2024-03-29T15:29:13Z
http://surface.syr.edu/do/oai/
oai:surface.syr.edu:phy_etd-1000
2010-09-13T15:46:04Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Beyond Standard Model physics on the lattice
Schneible, Joseph
2009-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Simon Catterall
Standard Model
Supersymmetry
Yang-Mills theory
Physical Sciences and Mathematics
Physics
We present numerical studies of two extensions of the Standard Model of particle physics. While there is no evidence which definitively disproves the Standard Model, there is much that hints at the existence of beyond Standard Model physics. The SM extension known as Technicolor seeks to resolve some of the theoretical discomfort with the Standard Model by replacing the elementary Higgs with a new strong sector, modeled closely on QCD. In order for Technicolor to achieve this goal and not be ruled out by experiment, it must exhibit dynamics which are different from QCD. We present simulation results which suggest that the specific model we studied, Minimal Walking Technicolor, has an infrared conformal fixed point, not seen in QCD. The other SM extension studied in this work, Supersymmetry, seeks to resolve issues with the Standard Model by proposing a symmetry between bosons and fermions. The model that we studied, [Special characters omitted.] = 4 Super Yang Mills, is dual to a Type IIB superstring theory in anti-de Sitter space. This superstring theory undergoes a Hawking-Page transition from a space containing a black hole to one without. In the dual SYM theory, one expects to see a phase transition between a confining and nonconfining phase. We present simulation results that hint at such a phase transition.
https://surface.syr.edu/phy_etd/3
oai:surface.syr.edu:phy_etd-1001
2010-09-13T15:50:54Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Biophysical applications of parallel cascade identification
Hawkins, Taviare L.
2009-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Edward D. Lipson
Parallel cascade identification
Intracellular signaling
Gesture recognition
Human-computer interfaces
Graphics and Human Computer Interfaces
Physical Sciences and Mathematics
Physics
Parallel Cascade Identification (PCI) (Korenberg, 1991) is an iterative algorithm that represents nonlinear systems by assembling parallel paths of cascades, each of which consists of a dynamic linear element followed by a static nonlinear element. This algorithm is based on a Volterra series expansion of a function that represents the unknown system. Knowing the stimulus (input) and response (output) of a system, we can use PCI to help us identify and model the dynamics of various systems. We have studied two biological systems: intracellular signal detection (in Chlamydomonas reinhardtii ) and gesture recognition.
For intracellular signal detection, a key feature in our approach is the use of multiple inputs with different dynamical rates. Since experimental data are not available yet, simulated results are shown.
For gesture recognition, parallel cascade has been modified to function as a classifier (Korenberg and Morin, 1997). We have adapted the parallel cascade to work in a real-time setting. Our experimental results on the gesture recognition project shows promise.
We conclude with a discussion on possible applications and open problems.
https://surface.syr.edu/phy_etd/2
oai:surface.syr.edu:phy_etd-1002
2010-09-14T17:20:20Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Dislocations in a vortex lattice and complexity of chlamydomonas ciliary beating
Amnuanpol, Sitichoke
2009-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Kenneth W. Foster
Chlamydomonas
Vortex lattice
Ciliary beating
Phototaxis
Superconductors
Biological and Chemical Physics
Physical Sciences and Mathematics
Physics
For the first topic the moving dislocations interrupt an orchestrating transport of vortices, leading to the different velocities of vortices at the different parts of a vortex lattice. Since the correlation of displacement grows algebraically in two dimensions rather than logarithmically in three dimensions, we emphasize the movement of edge dislocations on a single copper oxide plane. Effect of moving dislocations is particularly examined in connection to the velocity-force characteristics of vortices. Under the neutrality condition, the density of Burgers vectors of dislocations emerges in the equations of motion of vortices as a source term. Time evolution of the density of Burgers vectors is governed by a Fokker-Planck equation in which the drift and diffusion coefficients describe the interaction of dislocations and the thermal fluctuation, respectively. To find the Green's function of Fokker-Planck equation a perturbation series in the orders of drift coefficient which generally possesses the spatiotemporal dependence is constructed, analogous to the Born series of the time-dependent Schr¨odinger equation. In contrast, the drift coefficient shows up only with the even orders and the sign in a series alternates. Dislocations slow the velocity of vortices below their linear flux flow velocity, like the pinning. Free dislocations are more efficient to slow the velocity of vortices than interacting dislocations.
For the second topic the adaptation of Chlamydomonas ciliary beating to light stimulation during its phototaxis is studied by adopting a notion of memory believed to account for the slower responses. The influence of the past ciliary beating on the present one is expressed in terms of memory time estimated by a saturating point of Lipschitz number. Mutant cells seem to possess a memory time longer than wild type cells. Under a dark environment the ciliary beating shows strong time variability suitable for a temporal self-similarity study. The scaling exponent estimated by a detrended fluctuation analysis falls into two regimes, possibly signifying a behavioral transition, at least in the statistical sense, of ciliary beating. Using the time-delay coordinates of ciliary beating, the phase space of unknown differential equations underlying the phototaxis shows an 8-like shape.
https://surface.syr.edu/phy_etd/1
oai:surface.syr.edu:phy_etd-1003
2010-09-16T17:18:02Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Measurement of the branching fraction of D+ meson going to muon+ neutrino and the pseudoscalar decay constant fD+ using the full psi'' sample and search for neutral D meson going to proton-electron and neutral D meson going to antiproton-positron
Khalil, Sadia
2009-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Sheldon Stone
Branching fraction
Pseudoscalar decay constants
D mesons
Proton decay
fD form factor
Lepton violation
Physical Sciences and Mathematics
Physics
Two analysis have been described in this work. In the first analysis, we measure the decay constant of the D + meson by measuring [Special characters omitted.] ( D + [arrow right] μ + ν) = (3.86±0.32±0.09)×10 -4 using 818 pb -1 of data taken on the ψ(3770) resonance with the CLEO detector at the CESR collider. This is the full sample of taken acquired by CLEO-c at this center-of-mass energy. Taken along with precision measurement of the lifetime, and assuming | V cs | = | V ud |, we derive f D + = (205.8 ± 8.5 ± 2.5) MeV. We also set a 90% confidence upper limit on [Special characters omitted.] ( D + [arrow right] e + ν) < 8.8 × 10 -6 . In the second analysis we search for simultaneous baryon and lepton number violating decays of the D 0 meson. Specifically, we use 281 pb -1 of data taken on the ψ(3770) resonance with CLEO-c detector to look for decays D 0 [arrow right] p¯e + , D¯ 0 [arrow right] p¯e + , D 0 [arrow right] pe - and D¯ 0 [arrow right] pe - . We find no significant signals and set the following branching fraction upper limits: D 0 [arrow right] p¯e + ( D¯ 0 [arrow right] p¯e + ) < 1.1 × 10 -5 and D 0 [arrow right] pe - ( D¯ 0 [arrow right] pe - ) < 1.0 × 10 -5 , both at 90% confidence level.
https://surface.syr.edu/phy_etd/5
oai:surface.syr.edu:phy_etd-1004
2010-09-16T17:44:03Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Optimization and exact sampling algorithms for simulations of glassy materials
Thomas, Creighton Kays
2009-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
A. Alan Middleton
A. Alan Middleton
Spin glass
Planar lattice
Dimer
Ferromagnets
Condensed Matter Physics
Physical Sciences and Mathematics
Physics
Slow dynamics in disordered materials prohibits the direct simulation of their rich behavior. Clever algorithms are therefore needed to study low temperature states. This thesis presents three efficient algorithms for the numerical simulation of the Edwards Anderson model with Ising spins.
In two dimensions, the spin glass model is exactly mapped to a disordered dimer covering model. An efficient algorithm for finding minimum-weight perfect matchings is applied to rapidly compute the ground states of both models. Extended ground states in Ising spin glasses on a torus, which are optimized over all boundary conditions, are used to compute precise values for ground state energy densities.
Also, an exact sampling algorithm is presented that generates configurations of the two dimensional Ising spin glass at finite temperature, with probabilities proportional to their Boltzmann weights. The algorithm uses the above mapping, and adapts Wilson's algorithm for sampling dimer coverings on a planar lattice. This algorithm is recursive: it computes probabilities for spins along a "separator" that divides the sample in half. Given the spins on the separator, sample configurations for the two separated halves are generated by further division and assignment. For n spins and given floating point precision, the algorithm has an asymptotic run-time of O ( n 3/2 ).
Finally, a technique is presented for simulating the nonequilibrium behavior of spin glasses. "Patchwork dynamics" mimics the relaxation of a spin glass over a broad range of time scales by equilibrating or optimizing directly on successive length scales. This dynamics is used to study coarsening and to replicate memory effects for spin glasses and random ferromagnets. It is also used to find, with high confidence, exact ground states in large or toroidal samples.
https://surface.syr.edu/phy_etd/4
oai:surface.syr.edu:phy_etd-1006
2010-09-17T17:55:55Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Absolute branching fraction measurements for exclusives Ds semileptonic decays
Randrianarivony, Koloina A.
2008-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Marina Artuso
Branching fraction
Semileptonic decays
Cabibbo
Meson
Physical Sciences and Mathematics
Physics
We measure the absolute branching fractions of D s semileptonic decays where the hadron in the final state is one of [straight phi], η, η', [Special characters omitted.] , K *0 , and f 0 , using 2.8 × 10 5 e + e - [arrow right] D s [Special characters omitted.] decays collected in the CLEO-c detector at a center-of-mass energy close to 4170 MeV. We obtain [Special characters omitted.] ([Special characters omitted.] [arrow right] [straight phi] e + ν e ) = (2.29 ± 0.37 ± 0.11)%, [Special characters omitted.] ([Special characters omitted.] [arrow right] η e + ν e ) = (2.48 ± 0.29 ± 0.13)%, [Special characters omitted.] ([Special characters omitted.] [arrow right] η' e + ν e ) = (0.91 ± 0.33 ± 0.05)%, where the first uncertainties are statistical and the second are systematic. We also obtain [Special characters omitted.] ([Special characters omitted.] [arrow right] K 0 e + ν e ) = (0.37 ± 0.10 ± 0.02)%, and [Special characters omitted.] ([Special characters omitted.] [arrow right] K *0 e + ν e ) = (0.18 ± 0.07 ± 0.01)%, which are the first measurements of Cabibbo suppressed exclusive D s semileptonic decays, and, [Special characters omitted.] ([Special characters omitted.] [arrow right] f 0 e + ν e ) × [Special characters omitted.] ( f 0 [arrow right] π + π - ) = (0.13 ± 0.04 ± 0.01)%. This is the first direct evidence of a semileptonic decay including a scalar meson in the final state.
https://surface.syr.edu/phy_etd/9
oai:surface.syr.edu:phy_etd-1005
2010-09-17T17:31:05Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Unordinary order: A theoretical, computational and experimental investigation of crystalline order in curved space
Giomi, Luca
2009-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Mark John Bowick
Unordinary order
Crystalline order
Curved space
Geohetry
Condensed Matter Physics
Physical Sciences and Mathematics
Physics
Many systems in nature and the synthetic world involve ordered arrangements of units on two-dimensional surfaces. In this thesis I discuss the fundamental role payed by both the topology of the underlying surface and its detailed curvature. Topology dictates certain broad features of the defect structure of the ground state but curvature-driven energetics controls the detailed structured of ordered phases. Among the surprises are the appearance in the ground state of structures that would normally be thermal excitations and thus prohibited at zero temperature. Examples include excess dislocations in the form of grain boundary scars for spherical crystals above a minimal system size, dislocation unbinding for toroidal hexatics, interstitial fractionalization in spherical crystals and the appearance of well-separated disclinations for toroidal crystals. Much of the analysis leads to universal predictions that do not depend on the details of the microscopic interactions that lead to order in the first place. These predictions are subject to test by the many experimental soft and hard matter systems that lead to curved ordered structures such as colloidal particles self-assembling on droplets of one liquid in a second liquid. The defects themselves may be functionalized to create ligands with directional bonding. Thus nano to meso scale superatoms may be designed with specific valency for use in building supermolecules and novel bulk materials. Parameters such as particle number, geometrical aspect ratios and anisotropy of elastic moduli permit the tuning of the precise architecture of the superatoms and associated supermolecules. Thus the field has tremendous potential from both a fundamental and materials science/supramolecular chemistry viewpoint.
https://surface.syr.edu/phy_etd/10
oai:surface.syr.edu:phy-1000
2010-09-17T18:28:05Z
publication:coscde
publication:dphy
publication:phy
publication:cas
WebWork: Integrated Programming Environment Tools for National and Grand Challenges
Fox, Geoffrey C.
Furmanski, Wojtek
Chen, Marina
Rebbi, Claudio
Cowie, James H.
Working Paper
1995-01-01T08:00:00Z
integrated programming ; National Challenges ; Grand Challenges ; Integrated Challenge ; metaproblems ; parallel languages ; HPCC Initiative for Engineering e
Computer Engineering
Challenging-scale problems consistently demand solutions that fuse geographically distributed and
heterogeneous data, personnel, expertise, and resources. For example, national health care problems require collaboration among experts of fields as diverse as medical informatics, public policy, robotics, and high performance computing to solve problems ranging from telemedicine to cost management and quality control. Indeed, many National Challenges include Grand Challenges as subcomponents. We can pose the Integrated Challenge as the solution of etaproblems hosted on world-wide metacomputers linking all three aspects: simulation, information processing, and collaboration. We suggest a hybrid approach to Integrated Challenges that combines World-Wide Web (WWW) technologies with the current portable scalable software systems developed by the HPCC Initiative for Engineering and Scientific simulations. This combines the parallel languages and runtime of HPCC with the software engineering, collaboration and pervasive technology base of the WWW. The resultant
system will support collaborative rapid prototyping, applied to problem solving environments (PSE) at different scales. Support will extend from systems such as ELLPACK (parallel partial differential equation
PSE), NWChem (parallel computational chemistry PSE), MATLAB (uniprocessor matrix and signal
processing PSE), or Khoros (image processing/visualization PSE) in the simulation arena to complex National Challenges including education, manufacturing and healthcare. Roughly we consider the worldwide
metacomputer as a set of future generation WWW servers, each of which (individual workstation, cluster, SMP, or MPP) is implemented internally (in the closely-coupled homogeneous environment) using
appropriate HPCC technologies (e.g. HPF, MPI, PVM, Fortran-M, pC++, CC++, parallel Oracle, etc.). Then we link these servers together using generalized WWW technologies to allow executable program components to be published as services, and so create a distributed problem solving environment for prototyping large scale software.
https://surface.syr.edu/phy/1
oai:surface.syr.edu:phy_etd-1007
2010-09-17T18:29:25Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
A study of angular instability due to radiation pressure in LIGO gravitational wave detector
Hirose, Eiichi
2008-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Peter R. Saulson
Radiation pressure
Gravitational wave detector
Angular instability
Astrophysics and Astronomy
Atomic, Molecular and Optical Physics
Physical Sciences and Mathematics
Physics
We observed the effect of radiation pressure on the angular sensing and control system of the Laser Interferometer Gravitational-Wave Observatory (LIGO) interferometer's core optics at LIGO Hanford Observatory. This is the first measurement of this effect in a complete gravitational wave interferometer. Only one of the two angular modes survives with feedback control, since the other mode is suppressed when the control gain is sufficiently large. We developed a mathematical model to understand the physics of the system. The model indicates that the current system has substantial margin for higher laser power; angular instability due to radiation pressure won't occur until laser power reaches about eight times the power used in the initial LIGO configuration. This analysis was based on the degrees of freedom associated with differential motion between the mirrors in the interferometer's two arms. A more complete analysis including the common mode degrees of freedom will be left for future work.
https://surface.syr.edu/phy_etd/8
oai:surface.syr.edu:phy_etd-1008
2010-09-17T19:24:49Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Development and implementation of fully three-dimensional iterative reconstruction approaches in spect with parallel, fan- and cone-beam collimators
Ye, Hongwei
2008-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Andrzej Krol
Edward D. Lipson
Iterative reconstruction
Cone-beam collimators
Mesh-based reconstruction
Parallel collimators
Biological and Chemical Physics
Physical Sciences and Mathematics
Physics
As a noninvasive molecular imaging technique, Single Photon Emission Computed Tomography (SPECT) provides the distribution of radioactivity through reconstructing a projection dataset and allows us to visualize 3-dimentional (3D) functional information rather than anatomical information within a given organ. In this dissertation, three fully 3D iterative expectation maximization (EM) algorithms including maximum likelihood EM, ordered subsets EM and maximum a posteriori EM are studied in a variety of SPECT imaging systems with parallel-, fan-, and cone-beam collimators.
To improve reconstructed image quality with quantitative accuracy, volumetric system models including a strip-area system model (SASM), a fan-volume system model (FVSM) and a cone-volume system model (CVSM) have been developed and implemented for parallel-, fan-, and cone-beam collimators, respectively. These volumetric system models accurately describe the photon detection process due to system geometric factors, and provide more precise detection probability than other simple approximations such as a line-length system model (LLSM). Besides the novel development in system models, we have introduced almost all degrading factors into SPECT and investigated one-ray, two-ray or four-ray attenuation correction, distance-, and angle-dependent detector sensitivity and resolution correction, and scatter correction.
To suppress reconstruction noise in images, many regularization methods have also been compared and the 3D total variation method is the one most employed. Then, the performance of any new development has been evaluated both qualitatively and quantitatively through reconstruction of Monte Carlo simulations, experiments and clinical scans of numerical phantoms, physical phantoms, and patients. No matter what collimator is used in the projection acquisition, all results demonstrate that our new fully 3D iterative reconstruction approaches outperform the filtered backprojection (FBP) and EM algorithms with LLSM in terms of accuracy, bias, contrast-to-noise ratio, resolution, uniformity, and so on. Diagnostic performance of brain SPECT has also been evaluated on a group of patients and much higher sensitivity is observed in new approaches than that in FBP and EM-LLSM. To reduce the computational cost of our new reconstruction approaches, parallelized reconstruction using message passing interface has been proposed and studied on a cluster computer.
Finally, different from widely used pixel-based reconstruction, a method for nonuniform image sampling iterative reconstruction in SPECT has been developed and investigated, in which a content adaptive singularity-based triangular mesh (2D) is employed to represent images. Preliminary results indicate that mesh-based reconstruction is an efficient and promising approach with respect to image quality, computational cost, and potential in motion tracking.
https://surface.syr.edu/phy_etd/7
oai:surface.syr.edu:phy_etd-1009
2010-09-17T19:39:21Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Electronic transport in polyaniline films and polyaniline/silicon heterostructure solar cells
Wang, Weining
2008-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Electronic transport
Polyaniline films
Solar cells
Silicon heterostructures
Condensed Matter Physics
Physical Sciences and Mathematics
Physics
Experimental studies of the electronic transport and optical absorption in polyaniline (PANI) films and PANI/silicon heterostructure solar cells are reported. Most of the emeraldine salt PANI films were prepared by spin-casting from commercially prepared, acid-doped dispersions in xylene solution. It was discovered that diluting these dispersions about tenfold with additional xylene reduced the conductivity of the PANI films cast onto glass from 10 2 S/cm to 10 -4 S/cm or lower. This "dilution effect" is probably a variation of the well-known effect of dispersion pH upon the doping level of emeraldine salt PANI films. The optical absorption measurements on films from dispersions with varying xylene dilution were also similar to those previously reported for films prepared from dispersions with varying pH.
Heterostructure solar cells were prepared by casting p -type PANI films onto n-type crystalline silicon (c-Si) and onto hydrogenated amorphous silicon (a-Si:H) n/i structures. The open-circuit voltages ( V OC ) of the cells measured under strong (0.5 W/cm 2 ) white-light illumination probe the Fermi levels of the PANI films. Both the V OC measurements and temperature-dependent conductivity measurements on PANI films support a fixed bandedge model for transport. In this model, the variations in the film conductivities are determined by varying Fermi levels, and electronic transport occurs at a fixed valence bandedge level energy and bandedge conductivity (200 S/cm). We speculate that this bandedge is a mobility-edge. These conclusions differ significantly from previous models based on hopping transport or polaron bands.
For the PANI/Si cells, we conclude that V OC values of 0.7 V or higher are possible in principle, which would be of technological interest. The measured V OC values saturated at about 0.5 V for the highest conductivity films spun from xylene dispersions; high conductivity, water-based dispersions yielded a lower saturated V OC . We speculate that an interface effect is limiting V OC . No saturation was found for PANI/a-Si:H cells, but the largest V OC values of around 0.7 V are not of great technological interest.
https://surface.syr.edu/phy_etd/6
oai:surface.syr.edu:phy-1002
2010-09-20T14:52:47Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Group Cohomology, Modular Theory And Space-Time Symmetries
Brunetti, R.
Guido, D.
Longo, R.
Article
1994-01-01T08:00:00Z
group cohomology
modular theory
space-time symmetries
von Neumann algebras
extensions
Mathematics
The Bisognano-Wichmann property on the geometric behavior of the modular group of the von Neumann algebras of local observables associated to wedge regions in Quantum Field Theory is shown to provide an intrinsic sufficient criterion for the existence of a covariant action of the (universal covering of) the Poincar'e group. In particular this gives, together with our previous results, an intrinsic characterization of positive-energy conformal pre-cosheaves of von Neumann algebras. To this end we adapt to our use Moore theory of central extensions of locally compact groups by polish groups, selecting and making an analysis of a wider class of extensions with natural measurable properties and showing henceforth that the universal covering of the Poincar'e group has only trivial central extensions (vanishing of the first and second order cohomology) within our class.
https://surface.syr.edu/phy/3
oai:surface.syr.edu:phy-1004
2012-09-05T15:39:16Z
publication:coscde
publication:dphy
publication:phy
publication:cas
An Algebraic Approach to the Quantization of Cosntrained Systems: Finite Dimensional Examples
Tate, Ranjeet S.
Working Paper
1992-01-01T08:00:00Z
General Relativity and Quantum Cosmology
Cosmology, Relativity, and Gravity
<p>We discuss the statistical mechanics of magnetic flux lines in a finite-thickness slab of type-II superconductor. The long wavelength properties of a flux-line liquid in a slab geometry are described by a hydrodynamic free energy that incorporates the boundary conditions on the flux lines at the sample's surface as a surface contribution to the free energy. Bulk and surface weak disorder are modeled via Gaussian impurity potentials. This free energy is used to evaluate the two-dimensional structure factor of the flux-line tips at the sample surface. We find that surface interaction always dominates in determining the decay of translational correlations in the asymptotic long-wavelength limit. On the other hand, such large length scales have not been probed by the decoration experiments. Our results indicate that the translational correlations extracted from the analysis of the Bitter patterns are indeed representative of behavior of flux lines in the bulk.</p>
<p>124 pages, LaTeX (run twice before printing), SU-GP-92/8-1. (Minor corruption (extra blank line at line 2994) hopefully fixed.) Ph.D. Dissertation.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/6
oai:surface.syr.edu:phy-1003
2013-01-31T19:38:50Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Translational Correlations in the Vortex Array at the Surface of a Type-II Superconductor
Marchetti, M. Cristina
Nelson, David R.
Working Paper
1992-01-01T08:00:00Z
Condensed Matter
Physics
<p>We discuss the statistical mechanics of magnetic flux lines in a finite-thickness slab of type-II superconductor. The long wavelength properties of a flux-line liquid in a slab geometry are described by a hydrodynamic free energy that incorporates the boundary conditions on the flux lines at the sample's surface as a surface contribution to the free energy. Bulk and surface weak disorder are modeled via Gaussian impurity potentials. This free energy is used to evaluate the two-dimensional structure factor of the flux-line tips at the sample surface. We find that surface interaction always dominates in determining the decay of translational correlations in the asymptotic long-wavelength limit. On the other hand, such large length scales have not been probed by the decoration experiments. Our results indicate that the translational correlations extracted from the analysis of the Bitter patterns are indeed representative of behavior of flux lines in the bulk.</p>
<p>23 pages, 1 figure (not included), harvmac.tex macro needed (e-mail requests to marchetti@suhep.phy.syr.edu SU-CM-92-018</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/4
oai:surface.syr.edu:phy-1005
2012-09-21T13:20:14Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Vortex Dynamics in Superconducting Channels with Periodic Constrictions
Yu, Kang
Hesselberth, M.B.S.
Kes, P. H.
Plourde, B.L.T.
Working Paper
2010-01-01T08:00:00Z
superconductivity ; vortex dynamics
Physics
<p>Vortices confined to superconducting easy flow channels with periodic constrictions exhibit reversible oscillations in the critical current at which vortices begin moving as the external magnetic field is varied. This commensurability scales with the channel shape and arrangement, although screening effects play an important role. For large magnetic fields, some of the vortices become pinned outside of the channels, leading to magnetic hysteresis in the critical current. Some channel configurations also exhibit a dynamical hysteresis in the flux-flow regime near the matching fields.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/5
oai:surface.syr.edu:phy-1006
2010-09-20T18:16:23Z
publication:coscde
publication:dphy
publication:phy
publication:cas
To What Type of Logic Does the "Tetralemma" Belong?
Sorkin, Rafael D.
Working Paper
2010-01-01T08:00:00Z
logic ; general relativity and quantum cosmology ; quantum physics
Physics
Although the so called "tetralemma" might seem to be incompatible with any recognized scheme of logical inference, its four alternatives arise naturally within the "anhomomorphic" logics proposed recently in order to accommodate certain features of microscopic (i.e. quantum) physics. This suggests that non-classical logics of a similar type might have been known in ancient India.
plainTeX, 9 pages, no figures. Most current version is available at http://www.physics.syr.edu/~sorkin/some.papers/
https://surface.syr.edu/phy/7
oai:surface.syr.edu:phy_etd-1010
2010-09-20T17:16:43Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Hydrodynamics and rheology of mixtures of biopolymers and molecular motors
Ahmadi, Aphrodite
2008-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
M. Christina Marchetti
Active motor filaments
Cell motor activity
Hydrodynamics
Rheology
Biopolymers
Cytoskeleton dynamics
Condensed Matter Physics
Physical Sciences and Mathematics
Physics
Plasma and Beam Physics
I use tools and concepts from non-equilibrium statistical physics and polymer physics to describe the large-scale collective behavior of solutions of polar biofilaments and crosslinkers, in both quiescent and flowing solvents. I model the system as a polar liquid crystal with both excluded volume, and active interactions due to the crosslinkers. The role of mobile and stationary crosslinkers, which can induce filament alignment promoting polar or nematic order, in analogy with liquid crystalline phases, is taken into account. I start from a Smoluchowski equation for rigid filaments in solutions where pairwise crosslink-mediated interactions among the filaments yield translational and rotational currents. The large-scale properties of the system are described in terms of continuum equations for filament and motor densities, polarization and alignment tensor obtained by coarse-graining the Smoluchowski equation. The possible homogeneous states of the systems are obtained as stable solutions of the dynamical equations and are characterized in terms of experimentally accessible parameters. The activity of mobile crosslinkers, which cause exchange of forces and torques among the filaments, renders the homogeneous states unstable via filament bundling. Furthermore, I incorporate the coupling of the orientational order to flow into the hydrodynamic equations, and take into account the exchange of momentum between the filaments and the flowing solvent. Flow enhances the orientational order and suppresses orientational instability in the ordered states.
This model allows for an estimate of the various parameters in the hydrodynamic equations in terms of physical properties of the crosslinkers. Introducing a unified microscopic model to describe the non-equilibrium system of polar biofilaments and motor proteins with experimentally accessible parameters is the central result of this work.
https://surface.syr.edu/phy_etd/15
oai:surface.syr.edu:phy_etd-1013
2010-09-20T18:24:51Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Order, defects and dynamics on the sphere
Shin, Homin
2008-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Defect formation
Spherical crystals
Point defects
Liquid crystals
Elastic constants
Grain boundaries
Condensed Matter Physics
Physical Sciences and Mathematics
Physics
In this thesis we explore the rich physics of defect formation and dynamics in both spherical crystals and spherical nematics. For spherical crystals we describe the dynamics of scar defects and provide an analytical determination of the elastic spring constants of dislocations within scars using continuum elasticity theory with defect sources. Our results are compared to experimental observations of spherical crystals created in Pickering emulsions. We also discuss the remarkable behavior of interstitials and vacancies in spherical crystals. Interstitials or vacancies in a sufficiently large spherical crystal are, unlike in flat space, unstable to fragmentation into several individual dislocations, each of which glides towards the nearest disclination, eventually forming grain boundary scars. Using numerical simulations of the generalized Thomson problem we investigate interstitial fractionalization in some detail. We determine the dependence of final state energies on initial conditions and compare the position dependence of interstitial energies with the predictions of continuum elasticity theory on the sphere. For spherical nematics we combine Monte Carlo simulations and analytical calculations to explore the organization of defects in a system of hard and soft rods strictly confined to the two-dimensional sphere. In the ground state, orientationally ordered nematic phases with four type +1/2 disclinations are clearly observed. The disclinations are found to lie on a great circle rather than at the vertices of a tetrahedron. We explain this phenomenon in terms of the Frank free energy for an anisotropic spherical nematic in which splay deformations are far softer than bend deformations. We further examine the influence of the anisotropy of splay and bend elastic constants on the relative location of defects by minimizing the discretized strain energy from a mesoscopic Landau-de Gennes tensor model. From this we demonstrate that defect positions can be controlled by varying the anisotropy of the splay and bend moduli. Such control may prove useful in designing mesoscopic molecules and bulk materials by attaching ligands to functionalize the defect sites.
https://surface.syr.edu/phy_etd/12
oai:surface.syr.edu:phy_etd-1012
2010-09-20T18:18:11Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Numerical simulations for channel flow in disordered materials
Rodriguez Milla, Berta Elizabeth
2008-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Channel flow
Disordered materials
Numerical simulations
Pinning
Vortex flow
Type-II superconductors
Condensed Matter Physics
Physical Sciences and Mathematics
Physics
Results are presented for a coarse-grained model of collective transport in disordered materials, which generically incorporates both elastic and plastic viscous couplings. This model is motivated by the observation of both switching and macroscopic hysteresis in the driven transport of flux liquids (and in charge density waves). Such effects are ruled out when flux lines are coupled elastically. This anisotropic model is more general--it describes elastic channels interacting plastically. For exact mean-field calculations, this anisotropic model has a complex phase diagram with many interesting features, including a tricritical point which separates the non-hysteretic region from the region where there is a coexistence of stuck and moving states. This thesis examines this coarse-grained model in finite dimensions in detail to determine what features of the mean-field model remain. We integrate numerically the viscoelastic equation of motion, for two-channel, and two- and three-dimensional models. Strong evidence is presented for the existence of a tricritical point at finite viscosity in three dimensions. For the two-channel, and two-dimensional cases, it is unclear whether or not there is a critical point at zero viscous coupling. The shape of the phase diagram is significantly different from the mean-field calculations (e.g., the depinning force is viscous coupling-dependent). We find that the model exhibits hysteresis, which, for the two- and three-dimensional cases, increases with increasing viscous coupling strength, while for the two-channel case it may reach a constant value at a large viscous coupling. The hysteretic behavior might remain in the thermodynamic limit for the three-dimensional case. The equation of motion displays transient chaos, but we did not find evidence of strange attractors. This, along with sensitive dependence on initial conditions, complicates the analysis and conclusions.
https://surface.syr.edu/phy_etd/13
oai:surface.syr.edu:phy_etd-1011
2010-09-20T18:09:46Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Modifying gravity: Cosmic acceleration and the large scale structure of the universe
Silvestri, Alessandra
2008-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Modified gravity
Cosmic acceleration
Gravity
Structure formation
Cosmology
Late universe
Astrophysics and Astronomy
Physical Sciences and Mathematics
Physics
The late time acceleration of the universe poses a puzzle for modern cosmology. There exist several independent pieces of evidence pointing at cosmic acceleration, but we do not have yet a compelling theoretical explanation for it. General relativity applied to a universe that is homogeneous and isotropic on large scales and which contains only radiation and matter does not fit the observations. Assuming homogeneity and isotropy describes correctly the universe on large scales (as many observations indicate), the solution to this puzzle requires postulating either a new energy component, dark energy (be it the cosmological constant or a smoothly distributed dynamical field), or new gravitational dynamics on large scales - modified gravity .
In this thesis we focus on the latter approach and investigate models of modified gravity in the context of cosmic acceleration. In particular, we consider f ( R ) theories, in which the action for gravity is a general function of the Ricci scalar R , as well as constructing and studying a model inspired by these theories, which we dubbed Modified-Source Gravity.
For both theories we study in detail the cosmology of the homogeneous and isotropic background, to determine whether and under which conditions the models display a viable expansion history and satisfy the constraints imposed by local tests of gravity. We then proceed to study the evolution of the inhomogeneities around the background, which ultimately form large scale structure via gravitational instability. We apply the theory of cosmological perturbation to linear order in the fluctuations and derive predictions for the growth of structure.
We find that, in these theories of modified gravity, at the background level, there is sufficient freedom to reproduce the desired expansion history, and that this leads to a degeneracy between modified gravity and dark energy models. Nevertheless, at the level of large scale structure the modifications induce a peculiar scale dependent pattern of growth and the degeneracy may be broken. We find indeed that the Newton constant describing the clustering of dark matter is rescaled in a time- and scale-dependent way and can depart significantly from its general relativity value at late times on sufficiently small scales. Another peculiar feature common to the models we study is the introduction of a slip between the Newtonian potentials as well as a modification of their time dependence on small scales.
After identifying the signatures of the modifications at the level of large scale structure, we briefly give an overview of current and future surveys that could offer important tests of gravity.
https://surface.syr.edu/phy_etd/14
oai:surface.syr.edu:phy_etd-1014
2010-09-20T18:57:08Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Search for light Higgs in radiative decays of Upsilon(1 S)
Sultana, Nasra
2008-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Higgs boson
NMSSM
Upsilon
Energy
Physical Sciences and Mathematics
Physics
We have searched for non-SM-like CP-odd Higgs-boson ([Special characters omitted.] ) with [Special characters omitted.] < 2 m b in radiative decays of the Υ(1 S ), using 21.5M Υ(1 S ) mesons directly produced in e + e - annihilation. We investigate [Special characters omitted.] [arrow right] τ + τ - and [Special characters omitted.] [arrow right] μ + μ - decay channels. No significant signal is found. We obtain upper limits on the product of [Special characters omitted.] (Υ(1 S ) [arrow right] γ[Special characters omitted.] ) and [Special characters omitted.] ([Special characters omitted.] [arrow right] τ + τ - ) or [Special characters omitted.] ([Special characters omitted.] [arrow right] μ + μ - ). Our τ + τ - results are almost two orders of magnitude more stringent than previous upper limits. Our data provides no evidence for a Higgs state decaying to μ + μ - , with a mass of 214 MeV. Existence of such state was previously proposed as an explanation for 3 Σ + [arrow right] p μ + μ - events, with μ + μ - mass just above the kinematic threshold, claimed by the HyperCP experiment. Our results constrain NMSSM mode.
https://surface.syr.edu/phy_etd/11
oai:surface.syr.edu:phy_etd-1015
2010-09-21T17:36:04Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Topics in QCD and electroweak theory
Jora, Catalina Renata
2008-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Electroweak theory
Scalar mesons
Neutrinos
Physical Sciences and Mathematics
Physics
Two frontier topics, one in QCD (the light scalar meson puzzle) and the other one in electroweak theory (the problem of neutrino masses and mixings), are treated in this work.
We consider a generalized linear sigma model which contains two chiral nonets, one with a "two quark" structure, the other one with "four quark" fields. The model tries to explain, among other things, the inverted mass spectrum of the scalar mesons. We study this type of model using two approaches. The first one relies on the generating equations and leads to Ward identity type relations based only on the chiral symmetry. Using this approach we were able to find masses and mixings for the pseudoscalar and scalar states and also to prove that the low energy theorems for the pion-pion scattering hold in the limit of massless quarks. The second approach is based on a specific choice of terms in the Lagrangian. This allowed us to obtain information about all the masses and mixings in the model and also to give an exact numerical treatment for the scattering of two pions. Using both these methods we found consistently that while the lightest pseudoscalar states are mostly "quark-antiquark" structures, the lightest scalars have a large "four quark" component.
The instanton dynamics generates effective terms in the chiral lagrangian which violate explicitly the U(1) A symmetry. While the first term has the form of a determinant, the second one does not have a clear interpretation in the usual linear sigma model. We show that this this term can be viewed as mixing one between the "two quark" and "four quark" fields in our generalized model. This establishes a connections between the instanton approach and the effective Lagrangian one.
The leptonic mixing matrix in the electroweak theory is well known from experiments as being very close to the so-called tribimaximal form. This form is natural in the context of S 3 symmetry, where it is just the transformation matrix from the three dimensional defining representation to a sum of a one dimensional and a two dimensional irreducible representation. We consider that the S 3 symmetry holds as a first order approximation for the electroweak theory. We obtain in this way the desired tribimaximal form for the leptonic mixing matrix and we briefly discuss possible S 2 perturbation terms.
https://surface.syr.edu/phy_etd/18
oai:surface.syr.edu:phy_etd-1016
2010-09-21T17:52:06Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Toward a quantum dynamics for causal sets
Salgado, Roberto B.
2008-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Causal sets
Quantum gravity
Discrete spacetime
Posets
Physical Sciences and Mathematics
Physics
The Causal Set hypothesis for Quantum Gravity asserts that the smooth Lorentzian spacetime manifold of General Relativity is only an approximation to a fundamental microscopic discrete structure: a locally-finite partially-ordered set. The points of this set are akin to the point-events of the spacetime manifold, and the order-relations among these points are akin to the causal-relations among these point-events. The local-finiteness condition implies a fundamental discreteness and provides an important [conformal] factor needed for the continuum approximations.
In this dissertation, we address two aspects toward the formulation of a quantum dynamics for causal sets.
The first aspect concerns the dynamics of a zero-mass classical scalar field on a background causal set, Poisson-sampled from an Alexandrov interval in (1 + 1)-dimensional Minkowski spacetime. Our numerical simulations suggest that actions can be defined for such a scalar field, expressed solely in terms of the causal set and the scalar field, which approximates the corresponding classical action on the continuum Minkowski spacetime. This result may help us describe matter and gauge fields in a local and Lorentz-invariant way on a causal set, a discrete structure now being considered as the arena for spacetime physics. More importantly, it may help us formulate an action for the causal set itself, which would be used in a sum-over-histories approach to describe the quantum dynamics of causal sets.
The second aspect concerns Quantum Measure Theory, a new approach to quantum dynamics inspired by the sum-over-histories approach, which is better suited to formulating the dynamics of causal sets and of other alternative structures for spacetime. To better understand the mathematical structure underlying this new approach, we derive some algebraic identities involving the sum-rules of the Quantum Measure and its generalizations.
We conclude with a discussion on possible applications and open problems concerning these aspects.
https://surface.syr.edu/phy_etd/17
oai:surface.syr.edu:phy_etd-1017
2010-09-21T19:11:51Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Branching fraction measurements and SU(3) diagrammatic analysis of Cabibbo-suppressed D meson decays
Nisar, Shabana
2007-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
D meson
Cabibbo-suppressed decays
Branching fraction
SU(3) singlet
Physical Sciences and Mathematics
Physics
Using 281 p b -1 of data collected using the CLEO-c detector, we present new measurements of Cabibbo-suppressed decays of D mesons. We report first observations and measurements of the following branching fractions: B ( D 0 [arrow right] η'π 0 ) = (8.1±1.5±0.6)×10 -4 , B ( D 0 [arrow right] ηη) = (16.5±1.4±1.1)×10 -4 , B ( D 0 [arrow right] ηη') = (12.5±2.5±1.1)×10 -4 , B ( D 0 [arrow right] ηπ + π - ) = (10.9±1.3±1.0)×10 -4 , B ( D 0 [arrow right] η'π + π - ) = (4.3±1.6±0.6)×10 -4 , B ( D + [arrow right] ηπ + π 0 )=(13.8±3.2±1.6)×10 -4 , B ( D + [arrow right] η'π + π 0 ) = (15.8±4.3±2.6)×10 -4 . The uncertainties are statistical and systematic, respectively. We also present improved measurements of the branching fractions: B ( D 0 [arrow right] ηπ 0 ) = (6.3±1.0±0.4)×10 -4 , B ( D + [arrow right] ηπ + ) = (34.3±1.4±1.7)×10 -4 , and B ( D + [arrow right] η'π + ) = (44.4±2.5±2.6)×10 -4 . Several other modes are not observed, and we set the following 90% confidence level upper limits: B ( D 0 [arrow right] ηπ 0 π 0 ) ≤ (11.0×10 -4 ), B ( D 0 [arrow right] ηηπ 0 ) ≤ (21.0×10 -4 ), B ( D 0 [arrow right] ηηη) ≤ (8.0×10 -4 ), B ( D + [arrow right] ηK + ) ≤ (0.9×10 -4 ), and B ( D + [arrow right] η'K + ) ≤ (1.1×10 -4 ). We have also performed an SU (3) topological analysis and find reasonable agreement in the Color-suppressed and Exchange diagram amplitudes between Cabibbo-favored and Cabibbo-suppressed decays. If we allow for an additional singlet Exchange amplitude that couples to the SU(3) singlet part of the η and η', we find two solutions. The small solution which is about two standard deviations from 0, is favored over the larger solution, due to OZI-suppression.
https://surface.syr.edu/phy_etd/16
oai:surface.syr.edu:phy_etd-1018
2010-09-22T12:48:40Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Device physics of hydrogenated amorphous silicon solar cells
Liang, Jianjun
2006-12-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Eric Allan Schiff
Hydrogenated
Amorphous silicon
Solar cells
Physics
This dissertation reports measurements on and modeling of hydrogenated amorphous silicon (a-Si:H) nip solar cells. Cells with thicknesses from 200-900 nm were prepared at United Solar Ovonic LLC. The current density-voltage ( J-V ) relations were measured under laser illumination (685 nm wavelength, up to 200 mW/cm2) over the temperature range 240 K--350 K. The changes in the cells' open-circuit voltage during extended laser illumination (light-soaking) were measured, as were the cell properties in several light-soaked states. The J-V properties of cells in their as-deposited and light-soaked states converge at low-temperatures. Electromodulation spectra for the cells were also measured over the range 240 K--350 K to determine the temperature-dependent bandgap.
These experimental results were compared to computer calculations of J-V relations using the AMPS (©Pennsylvania State University) computer code. Bandtail parameters (for electron and hole mobility and recombination) were consistent with published drift-mobility and transient photocurrent measurements on a-Si:H. The open-circuit voltage and power density measurements on as-deposited cells, as a function of temperature and thickness, were predicted well. The calculations support a general "hole mobility limited" approach to analyzing a-Si:H solar cells, and indicate that the doped electrode layers, the as-deposited density of dangling bonds, and the electron mobility are of secondary importance to as-deposited cells.
For light-soaked a-Si:H solar cells, incorporation of a density of dangling bonds in the computer calculations accounted satisfactorily for the power and open-circuit voltage measurements, including the low-temperature convergence effect. The calculations indicate that, in the light-soaked state at room-temperature, electron recombination is split nearly evenly between holes trapped in the valence bandtail and holes trapped on dangling bonds. The result supports Stutzmann, Jackson, and Tsai's 1985 conjecture that dangling bond creation results only from bandtail recombination events.
We compared the predictions of the hydrogen-collision model proposed by Branz with the kinetics of the open-circuit voltage as light-soaking progressed. We obtained satisfactory agreement for the initial phases of light-soaking with the conjecture that only bandtail recombination leads to dangling bond creation, and the computer calculations for this recombination channel's diminishment in the cell as the dangling bond density grows.
https://surface.syr.edu/phy_etd/19
oai:surface.syr.edu:phy-1007
2010-09-22T13:52:47Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Nonperturbative Results for Yang-Mills Theories
Sannino, Francesco
Schechter, Joseph
Working Paper
2010-01-01T08:00:00Z
High Energy Physics
Phenomenology
High Energy Physics
Lattice
Physics
Some non perturbative aspects of the pure SU(3) Yang-Mills theory are investigated assuming a specific form of the beta function, based on a recent modification by Ryttov and Sannino of the known one for supersymmetric gauge theories. The characteristic feature is a pole at a particular value of the coupling constant, g. First it is noted, using dimensional analysis, that physical quantities behave smoothly as one travels from one side of the pole to the other. Then it is argued that the form of the integrated beta function g(m), where m is the mass scale, determines the mass gap of the theory. Assuming the usual QCD value one finds it to be 1.67 GeV, which is in surprisingly good agreement with a quenched lattice calculation. A similar calculation is made for the supersymmetric Yang-Mills theory where the corresponding beta function is considered to be exact.
RevTeX, 2colmuns, 6 pages and 7 figures
https://surface.syr.edu/phy/10
oai:surface.syr.edu:phy-1008
2012-12-05T16:01:23Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Light Scalar Puzzle in QCD
Fariborz, Amir H.
Jora, Renata
Schechter, Joseph
Working Paper
2010-01-01T08:00:00Z
Effective chiral Lagrangian
QCD
Light scalar mesons
Physics
<p>An approach to understanding the light scalar meson spectroscopy is briefly reviewed</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/9
oai:surface.syr.edu:phy-1009
2012-09-05T15:41:04Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Logic is to the Quantum as Geometry is to Gravity
Sorkin, Rafael D.
Working Paper
2010-01-01T08:00:00Z
Quantum Physics
General Relativity
Quantum Cosmology
High Energy Physics Theory
Physics
<p>will propose that the reality to which the quantum formalism implicitly refers is a kind of generalized history, the word history having here the same meaning as in the phrase sum-over-histories. This proposal confers a certain independence on the concept of event, and it modifies the rules of inference concerning events in order to resolve a contradiction between the idea of reality as a single history and the principle that events of zero measure cannot happen (the Kochen-Specker paradox being a classic expression of this contradiction). The so-called measurement problem is then solved if macroscopic events satisfy classical rules of inference, and this can in principle be decided by a calculation. The resulting conception of reality involves neither multiple worlds nor external observers. It is therefore suitable for quantum gravity in general and causal sets in particular.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/8
oai:surface.syr.edu:phy_etd-1019
2010-09-23T17:08:08Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Establishment of Bs meson production at the psi(5S) energy using beauty and charm decays
Sia, Radia
2007-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Sheldon Stone
Meson production
Beauty
Charm
Psi(5S)
Physical Sciences and Mathematics
Physics
The Υ(5S) resonance has long been thought to be a source of B s mesons, since it is massive enough to produce B s B s pairs. In this work, we establish the presence of B s mesons at the Υ(5S) energy and measure its production rate using both beauty and charm decays. We use all the e + e - collision data collected by the CLEO III detector at the Υ(5S) and at the Υ(4S) resonance energies. This data consists of 0.423 fb -1 on the Υ(5S) resonance, 6.34 fb -1 on the Υ(4S) and 2.32 fb -1 in the continuum below the Υ(4S). We also use 281 pb -1 data accumulated with the CLEO-c detector on the ψ (3770) resonance and another 195 pb -1 taken in the region near 4170 MeV center-of-mass energy.
In the first analysis, we measure the asymmetry of D s meson production in Υ(4S) and Υ(5S) decays as [Special characters omitted.] (Υ(5 S ) [arrow right] D s X )/[Special characters omitted.] (Υ(4S) [arrow right] D s X ) = (2:5 ± [Special characters omitted.] ). We take advantage of this asymmetry, which is due to the difference of B and B s meson production in the decays of the two resonances, to establish B s meson production in Υ(5S) decays and measure its fraction, f s , as (16:8±[Special characters omitted.] )% using a theoretical estimate of (92±11)% for the inclusive branching ratio [Special characters omitted.] ( B s [arrow right] D s X ). We also show the dependence of this measurement on the [Special characters omitted.] [arrow right] [straight phi]π + branching fraction.
Knowledge of the B s production rate at the Υ(5S) resonance is imperative for B s studies at the Υ(5S) using current B -factories, and for future e + e - Super- B Factories. We show in the second part of this work that the determination of f s in a model independent manner requires several tens of fb -1 . We present a method that provides a measurement of f s using the relative rates of like-sign versus opposite sign dileptons; the like-sign leptons result from B 0 and B s mixing. In addition, we show that determining the rates of single, double and triple [Special characters omitted.] mesons provides an alternative way of finding f s .
To constrain our knowledge of B s production at the Υ(5S) by making other measurements with other model dependencies, we examine CLEO-c data for other particle species than D s , that are produced with much higher rate in B s meson decays than in B meson decays. Such particle like η, η' and [straight phi], with their ss quark composition, are expected to be enhanced in D s than in D meson decays. We therefore measure the inclusive branching fractions of charm mesons, namely D 0 , D + and [Special characters omitted.] , into η X , η' X , and [straight phi] X decays. We find that the rates from [Special characters omitted.] are much larger than from D 0 and D + .
We use the inclusive [straight phi] meson yields which is higher by one order of magnitude in D s than in D decays to make a second measurement of [Special characters omitted.] (Υ(5 S ) [arrow right] [Special characters omitted.] ) using our model estimate of [Special characters omitted.] ( B s [arrow right] [straight phi] X ). We measure [Special characters omitted.] (Υ(5 S ) [arrow right] [straight phi] X ) = (13:8 ± [Special characters omitted.] )% and [Special characters omitted.] (Υ(4 S ) [arrow right] [straight phi] X ) = (7:1 ± 0:1 ± 0:6)%, the ratio of the two rates is (1:9 ± [Special characters omitted.] ). This is the first measurement of the [straight phi] meson yield from the Υ(5S). We measure f s = (24:6±[Special characters omitted.] )% and we also report on the total Υ(5 S ) hadronic cross section above continuum to be σ( e + e - Υ(5 S )) = (0:301 ± 0:002 ± 0:039) nb. This allows us to extract the fraction of B mesons as (58:9 ± 10:0 ± 9:2)%, equal to 1- f s . Averaging the three methods gives a model dependent result of f s = ([Special characters omitted.] )%.
https://surface.syr.edu/phy_etd/22
oai:surface.syr.edu:phy_etd-1020
2010-09-23T17:55:30Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Leptonic decays of charged D and Ds mesons
Menaa, Nabil
2007-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Sheldon Stone
Leptonic decays
D mesons
Physical Sciences and Mathematics
Physics
Using 281 pb -1 of data taken on the ψ(3770) resonance and 314 pb -1 of data near or at 4170 MeV collected with the CLEO-c detector, we present two analyses to study the purely leptonic decays of charmed and charmed strange charged mesons.
In the first analysis, we extract a relatively precise value for the decay constant of the D + meson by measuring [Special characters omitted.] ( D + [arrow right] μ + ν) = (4.40 ± [Special characters omitted.] ) × 10 -4 . We find f D + = (222.6 ± [Special characters omitted.] ) MeV, and compare with current theoretical calculations. We also set a 90% confidence upper limit on [Special characters omitted.] ( D + [arrow right] e + ν) < 2.4 × 10 -5 which constrains new physics models. Finally with this data sample, we test whether or not the τ lepton manifests the same couplings as the μ lepton by investigating the relative decay rates in purely leptonic D + meson decays. We limit [Special characters omitted.] ( D + [arrow right] τ + ν) < 2.1 × 10 -3 at 90% confidence level (C. L.), thus allowing us to place the first upper limit on the ratio R = Γ ( D + [arrow right] τ + ν)/Γ( D + [arrow right] μ + ν). The ratio of R to the Standard Model expectation of 2.65 then is <1.8 at 90% C. L., consistent with the prediction of lepton universality.
In the second analysis, we examine e + e - [arrow right] [Special characters omitted.] and [Special characters omitted.] interactions at 4170 MeV using the CLEO-c detector in order to measure the decay constant [Special characters omitted.] . We use the [Special characters omitted.] [arrow right] [cursive l] + ν channel, where the [cursive l] + designates either a μ + or a τ + , when the τ + [arrow right] π + ν. Analyzing both modes independently, we determine [Special characters omitted.] ([Special characters omitted.] [arrow right] μ + ν) = (0.594 ± 0.066 ± 0.031)%, [Special characters omitted.] ([Special characters omitted.] [arrow right] τ + ν) = (8.0 ± 1.3 ± 0.4)%. We also analyze them simultaneously to find an effective value of [Special characters omitted.] ([Special characters omitted.] [arrow right] μ + ν) = (0.621 ± 0.058 ± 0.032)% and extract [Special characters omitted.] = 270 ± 13 ± 7 MeV. Combining with our previous determination of [Special characters omitted.] ( D + [arrow right] μ + ν), we also find the ratio [Special characters omitted.] = 1.21 ± 0.11 ± 0.04. We compare with current theoretical estimates. Finally, we limit [Special characters omitted.] ([Special characters omitted.] [arrow right] e + ν) < 1.3 × 10 -4 at 90% confidence level.
https://surface.syr.edu/phy_etd/21
oai:surface.syr.edu:phy_etd-1021
2010-09-23T18:25:51Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Parity-violating electron scattering on hydrogen and helium and strangeness in the nucleon
Benaoum, Hachemi
2007-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Paul Souder
Hydrogen
Helium
Parity violation
Strange form factors
Polarized electron scattering
Physical Sciences and Mathematics
Physics
The HAPPEX II measurement of the parity violating asymmetry A PV for longitudinally polarized 3 GeV electrons from both hydrogen and 4 He cryogenic targets, at a small scattering angle (6°), is reported in this thesis. The asymmetry for hydrogen is a function of a linear combination of [Special characters omitted.] and [Special characters omitted.] , the strange quark contributions to the electric and magnetic form factors of the nucleon respectively, and that for 4 He is a function solely of [Special characters omitted.] . The combination of the two measurements therefore allows [Special characters omitted.] and [Special characters omitted.] to be separately determined. The 4 He result is [Special characters omitted.] = +6.40 ± 0.23 (stat) ± 0.12 (syst) ppm. The hydrogen result is [Special characters omitted.] = -1.58 ± 0.12 (stat) ± 0.04 (syst) ppm. The strange quark form factors extracted from these asymmetries are [Special characters omitted.] = 0.002 ± 0.014 ± 0.007 at < Q 2 >= 0.077 GeV 2 , and [Special characters omitted.] + 0.09[Special characters omitted.] = 0.007 ± 0.011 ± 0.006 at < Q 2 >= 0.109 GeV 2 . These results significantly improve constraints on the electric and magnetic strange form factors with an unprecedented precision.
https://surface.syr.edu/phy_etd/20
oai:surface.syr.edu:phy-1011
2012-09-05T15:49:42Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Feasibility of Measuring the Shapiro Time Delay over Meter-Scale Distances
Ballmer, Stefan
Marka, S.
Shawhan, P.
Working Paper
2009-01-01T08:00:00Z
General Relativity
Quantum Cosmology
Physics
<p>The time delay of light as it passes by a massive object, first calculated by Shapiro in 1964, is a hallmark of the curvature of space-time. To date, all measurements of the Shapiro time delay have been made over solar-system distance scales. We show that the new generation of kilometer-scale laser interferometers being constructed as gravitational wave detectors, in particular Advanced LIGO, will in principle be sensitive enough to measure variations in the Shapiro time delay produced by a suitably designed rotating object placed near the laser beam. We show that such an apparatus is feasible (though not easy) to construct, present an example design, and calculate the signal that would be detectable by Advanced LIGO. This offers the first opportunity to measure space-time curvature effects on a laboratory distance scale.</p>
<p>13 pages, 6 figures; v3 has updated instrumental noise curves plus a few text edits; resubmitted to Classical and Quantum Gravity</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/12
oai:surface.syr.edu:phy-1010
2012-09-05T15:41:55Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Is the Spacetime Metric Euclidean Rather than Lorentzian?
Sorkin, Rafael D.
Working Paper
2009-01-01T08:00:00Z
General Relativity
Quantum Cosmology
High Energy Physics Theory
Mathematical Physics
Quantum Physics
Physics
<p>My answer to the question in the title is "No". In support of this point of view, we analyze some examples of saddle-point methods, especially as applied to quantum "tunneling" in nonrelativistic particle mechanics and in cosmology. Along the way we explore some of the interrelationships among different ways of thinking about path-integrals and saddle-point approximations to them.</p>
<p>plainTeX, 21 pages, 1 figure (in color). Correction made to eq. 6: a previous version erroneously gave Re(f(z)) rather than Im(f(z)). (Thanks to Adam Brown for this correction.) Most current version is available at this http URL (or wherever my home-page may be). To appear in {\it Recent Research in Quantum Gravity}, ed. A. Dasgupta</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/13
oai:surface.syr.edu:phy-1012
2012-09-21T13:32:42Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Picovoltmeter for Probing Vortex Dynamics in a Single Weak-Pinning Corbino Channel
Heitmann, T. W.
Yu, Kang
Song, C.
DeFeo, M P.
Plourde, B.L.T.
Working Paper
2008-01-01T08:00:00Z
Superconductivity
Physics
<p>We have developed a picovoltmeter using a Nb dc Superconducting QUantum Interference Device (SQUID) for measuring the flux-flow voltage from a small number of vortices moving through a submicron weak-pinning superconducting channel. We have applied this picovoltmeter to measure the vortex response in a single channel arranged in a circle on a Corbino disk geometry. The circular channel allows the vortices to follow closed orbits without encountering any sample edges, thus eliminating the influence of entry barriers.</p>
<p>4 pages, 3 figures, submitted to Review of Scientific Instruments</p>
<p>First author and SU authors listed, for additional authors see article.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/11
oai:surface.syr.edu:phy_etd-1022
2010-09-24T12:33:41Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Exact supersymmetry on the lattice
Ghadab, Sofiane
2006-12-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Simon Catterall
Supersymmetry
Lattice
Yang-Mills theory
Physics
We describe a new approach of putting supersymmetric theories on the lattice. The basic idea is to discretize a twisted formulation of the (extended) supersymmetric theory. One can think about the twisting as an exotic change of variables that modifies the quantum numbers of the original fields. It exposes a scalar nilpotent supercharge which one can be preserved exactly on the lattice. We give explicit examples from sigma models and Yang-Mills theories. For the former, we show how to deform the theory by the addition of potential terms which preserve the supersymmmetry and play the role of Wilson terms, thus preventing the appearance of doublers. For the Yang-Mills theories however, one can show that their twisted versions can be rewritten in terms of two real Kähler-Dirac fields whose components transform into each other under the twisted supersymmetry. Once written in this geometrical language, one can ensure that the model does not exhibit spectrum doubling if one maps the component tensor fields to appropriate geometrical structures in the lattice. Numerical study of the O (3) sigma models and U (2) and SU (2) Yang-Mills theories for the case [Special characters omitted.] = D = 2 indicates that no additional fine tuning is needed to recover the continuum supersymmetric models.
https://surface.syr.edu/phy_etd/28
oai:surface.syr.edu:phy-1013
2012-07-30T15:56:00Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Isotropic-Cholesteric Transition of a Weakly Chiral Elastomer Cylinder
Xing, Xiangjun
Baskaran, Aparna
Working Paper
2008-01-01T08:00:00Z
Soft Condensed Matter
Physics
<p>When a chiral isotropic elastomer is brought to low temperature cholesteric phase, the nematic degree of freedom tends to order and form a helix. Due to the nemato-elastic coupling, this also leads to elastic deformation of the polymer network that is locally coaxial with the nematic order. However, the helical structure of nematic order is incompatible with the energetically preferred elastic deformation. The system is therefore frustrated and appropriate compromise has to be achieved between the nematic ordering and the elastic deformation. For a strongly chiral elastomer whose pitch is much smaller than the system size, this problem has been studied by Pelcotivs and Meyer, as well as by Warner. In this work, we study the isotropic-cholesteric transition in the weak chirality limit, where the pitch is comparable or much larger than system size. We compare two possible solutions: a helical state as well as a double twist state. We find that the double twist state very efficiently minimizes both the elastic free energy and the chiral nematic free energy. On the other hand, the pitch of the helical state is strongly affected by the nemato-elastic coupling. As a result this state is not efficient in minimizing the chiral nematic free energy.</p>
<p>7 pages, 2 eps figures</p>
https://surface.syr.edu/phy/14
oai:surface.syr.edu:phy_etd-1025
2010-09-24T13:37:21Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
First measurements of the exclusive decays of the upsilon(5S) to B* meson B* bar meson pion pion final states and improved B*(s) meson mass measurements
Zhang, Hongshan (Kevin)
2006-11-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Steven Blusk
Upsilon
B mesons
Exclusive reconstruction
Cross section
particle physics
Physics
Using 420 pb -1 of data collected on the Υ(5 S ) resonance, we exploit exclusive reconstruction of B mesons in several channels to measure or set upper limits on the decay of the Υ(5 S ) into B ([low *]) B ([low *]) (π)(π) final states for the first time in the world. Using 25 B decay modes, we measure the inclusive B cross-section to be σ(Υ(5 S ) [arrow right] BBX ) = (0:177 ± 0.030±0.016) nb. We also establish first measurements of the production rate for Υ(5 S ) [arrow right] B * B * and Υ(5 S ) [arrow right] B B *, and measure their cross-sections to be: σ(Υ(5 S ) [arrow right] B * B *) = (0.119 ± 0.023 ± 0.013) nb, σ(Υ(5 S ) [arrow right] BB *) = (0.039 ± 0.015 ± 0.005) nb. In other decay channels, we establish 90% confidence level limits of σ(Υ(5 S ) [arrow right] BB ) < 0.038 nb, σ(Υ(5 S ) [arrow right] B ([low *]) B ([low *]) π) < 0.051 nb and σ(Υ(5 S ) [arrow right] BB ππ) < 0.029 nb. We also extract the most precise value of the [Special characters omitted.] mass to date, which is measured to be M ([Special characters omitted.] ) = (5411.7 ± 1.6 ± 0.6) MeV.
https://surface.syr.edu/phy_etd/25
oai:surface.syr.edu:phy_etd-1026
2010-09-24T13:42:54Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
First Observation of psi(3770) decays to photon chi(cJ)
Butt, Jamila Bashir
2006-05-01T07:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Tomasz Skwarnicki
Psi mesons
Chi mesons
Non-DDbar decays
Electromagnetic decays
particle physics
Physics
Using e + e - collision data acquired with the CLEO detector at CESR, we observe the non- DD¯ decay [psi](3770) [arrow right] [gamma][chi] cJ . We observe a highly significant signal (significance of 12.6[sigma]) for [psi](3770) [arrow right] [gamma][chi] c 0 , detected in four exclusive decays modes containing charged pions and kaons. For [psi](3770) [arrow right] [gamma][chi] c1 , we observe a signal of 6.6[sigma] significance in the two-photon cascades to J| [psi] ( J| [psi] [arrow right] [cursive l] + [cursive l] - ) and of 3.6[sigma] significance in four exclusive decays modes containing charged pions and kaons. We determine [Special characters omitted.] ([psi](3770) [arrow right] [gamma][chi] c 0 ) = (7.3 ± 0.9) × 10 -3 and [Special characters omitted.] ([psi](3770) [arrow right] [gamma][chi] c 1 ) = (2.9 ± 0.8) × 10 -3 . We also set 90% C.L. upper limits for the transition to [chi] c 2 : [Special characters omitted.] < 0.9 × 10 -3 .
https://surface.syr.edu/phy_etd/24
oai:surface.syr.edu:phy_etd-1023
2010-09-24T13:03:57Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Experimental investigations towards production of hyperpolarized xenon-129 through the condensed state
Balakishiyeva, Durdana Nazim
2006-08-01T07:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Arnold Honig
Hyperpolarized
Condensed state
Xenon-129
condensation
Physics
Nuclear spin relaxation of 129 Xe in solid xenon was investigated over a wide range of oxygen content, in the temperature range between 1.4 and 160K and in magnetic fields between 2.5 and 10 kOe. From the nuclear spin lattice relaxation measurements between 1.4 and 4.2K, the magnetic energy structure of the O 2 impurity was determined, notably a crystal field D term of 0.19 meV. An anomalous temperature dependence of the T 1n in that range was explained with a paramagnetic impurity model based on the magnetic structure. Dynamic nuclear polarization of the 129 Xe was observed near 2.0 K and a field of 2.8 kOe when moderate concentrations of the radical TEMPO were introduced into liquid xenon and the mixture frozen quickly. Nuclear spin polarization enhancement factors of up to 300 were obtained for the 129 Xe with several hundred milliwatts microwave pumping at frequencies in the 9 GHz range. The results cannot be explained with the unresolved 'solid effect' model, whereas the spin temperature reservoir theory is a good candidate. A moderately oxygen doped 129 Xe sample was brought from 1.4K to 150K quickly enough for the resulting material to be hyperpolarized with a polarization enhancement of about 80 with respect to the final T and B values.
https://surface.syr.edu/phy_etd/27
oai:surface.syr.edu:phy_etd-1024
2010-09-24T13:30:28Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
First indications of causal set cosmology
Ahmed, Maqbool
2006-11-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Rafael Sorkin
Causal set
Cosmology
Dark energy
Astrophysics
Cosmology, Relativity, and Gravity
A variety of observations indicate that the universe is dominated by a so-called "dark energy" with an effective negative pressure, one possibility for which is a cosmological constant. If the dark energy is a cosmological constant, a fundamental question is: Why has it become relevant at so late an epoch, making today the only time in the history of the universe at which the cosmological constant is of order the ambient density. We explore an answer to this question based on the conjugacy - and resulting uncertainty relationship - expected between spacetime volume and the cosmological term in any theory of quantum gravity (and clearly visible in, say, unimodular gravity), and on spacetime discreteness at the fundamental level. The first of these predicts fluctuations in the cosmological constant, and then a fundamentally discrete theory like causal set theory predicts the magnitude of these fluctuations. The resulting ansatz yields a fluctuating cosmological "constant" which is always of order the ambient energy density. The model is not only structurally stable but also does extremely well on the observational side.
https://surface.syr.edu/phy_etd/26
oai:surface.syr.edu:phy_etd-1027
2010-09-24T17:43:27Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Symmetries in noncommutative physics
Qureshi, Babar Ahmed
2007-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Noncommutative spaces
Symmetries
Twisted symmetries
Elementary Particles and Fields and String Theory
Physical Sciences and Mathematics
Physics
Quantum field theories on noncommutative spaces are an important area of research in high energy physics because of their importance as a tool to capture aspects of Planck scale physics, where one expects the spacetime to show noncommutative behavior, their emergence in string theory and also as a tool to regularize quantum field theories. An important issue in the study of noncommutative quantum field theories (NCQFT's) is that of symmetries. Introduction of noncommutativity explicitly breaks Lorentz invariance. However, the classical actions of noncommutative field theories are invariant under a twisted action of the Poincaré group. In this thesis we study the consequences of such twisted symmetries at the quantum level. We give complete construction of quantum field theories covariant under the twisted Poincaré action including the explicit form of the twisted Poincaré generators. We find some striking results such as twisting of Bose and Fermi statistics and removal of UV-IR mixing in the non-gauge theories. We also apply the idea of twisting to gauge symmetries and construct gauge theories covariant under twisted action of gauge and Poincaré groups. Any gauge group can be treated using our formulation, unlike the ordinary noncommutative gauge theories where only U ( N ) groups admit direct treatment. We derive the Feynman rules for this theory and find interesting results such as violation of Pauli principle and violation of Lorentz invariance due to failure of a generalized form of locality. We also treat the twisted form of supersymmetry. Finally we study the formulation of supersymmetry on fuzzy sphere and construct fuzzy supersymmetric instanton. We find the zero modes in the instanton sector and study their index theory.
https://surface.syr.edu/phy_etd/23
oai:surface.syr.edu:phy-1017
2012-01-20T21:11:18Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Topology of Smectic Order on Compact Substrates
Xing, Xiangiun
Working Paper
2007-01-01T08:00:00Z
Condensed Matter
Physics
<p>Smectic orders on curved substrates can be described by differential forms of rank one (1-forms), whose geometric meaning is the differential of the local phase field of density modulation. The exterior derivative of 1-form is the local dislocation density. Elastic deformations are described by superposition of exact differential forms. Applying this formalism to study smectic order on torus as well as on sphere, we find that both systems exhibit many topologically distinct low energy states, that can be characterized by two integer topological charges. The total number of low energy states scales as the square root of the substrate area. For smectic on a sphere, we also explore the motion of disclinations as possible low energy excitations, as well as its topological implications.</p>
<p>4 pages, 3 eps figures, accepted by physical review letters</p>
https://surface.syr.edu/phy/18
oai:surface.syr.edu:phy-1018
2012-09-05T15:23:17Z
publication:coscde
publication:dphy
publication:phy
publication:cas
The BTeV RICH Front End Electronics
Artuso, Marina
Presentation
2005-01-01T08:00:00Z
nstrumentation and Detectors
High Energy Physics Experiments
Physics
<p>We report on the design and testing of novel mixed analog and digital front end ASICs custom made for the single photon detectors considered for the BTeV RICH system. The key features are reviewed, as well as results achieved using electronics bench tests and beam studies.</p>
<p>7 pages, 4 figures, talk given at the 5th International Workshop on Ring Imaging Cherenkov Counters (RICH2004)</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/17
oai:surface.syr.edu:phy-1016
2013-01-29T17:44:34Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Numerical Results for the Ground-State Interface in a Random Medium
Middleton, Alan
Working Paper
1995-01-01T08:00:00Z
Condensed Matter
Physics
<p>The problem of determining the ground state of a $d$-dimensional interface embedded in a $(d+1)$-dimensional random medium is treated numerically. Using a minimum-cut algorithm, the exact ground states can be found for a number of problems for which other numerical methods are inexact and slow. In particular, results are presented for the roughness exponents and ground-state energy fluctuations in a random bond Ising model. It is found that the roughness exponent $\zeta = 0.41 \pm 0.01, 0.22 \pm 0.01$, with the related energy exponent being $\theta = 0.84 \pm 0.03, 1.45 \pm 0.04$, in $d = 2, 3$, respectively. These results are compared with previous analytical and numerical estimates.</p>
<p>10 pages, REVTEX3.0; 3 ps files (separate:tar/gzip/uuencoded) for figures</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/19
oai:surface.syr.edu:phy-1015
2010-09-28T11:36:36Z
publication:coscde
publication:dphy
publication:phy
publication:cas
A Historical Perspective on Cancer
Sorkin, Rafael D,
Report
2000-01-01T08:00:00Z
Biological physics. medical physics
cell behavior
molecular networks
tissues and organs
Cancer Biology
Cell and Developmental Biology
It is proposed that cancer results from the breakdown of universal control mechanisms which developed in mutual association as part of the historical process that brought individual cells together into multi-cellular communities. By systematically comparing the genomes of uni-celled with multi-celled organisms, one might be able to identify the most promising sites for intervention aimed at restoring the damaged control mechanisms and thereby arresting the cancer.
3 pages, plainTeX, no figures
https://surface.syr.edu/phy/15
oai:surface.syr.edu:phy-1014
2010-09-28T11:31:42Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Regge Calculus as a Fourth Order Method in Numerical Relativity
Miller, Mark A.
Working Paper
1995-02-27T08:00:00Z
Regge calculus
General relativity
Mathematics
Physics
The convergence properties of numerical Regge calculus as an approximation to continuum
vacuum General Relativity is studied, both analytically and numerically. The
Regge equations are evaluated on continuum spacetimes by assigning squared geodesic
distances in the continuum manifold to the squared edge lengths in the simplicial manifold.
It is found analytically that, individually, the Regge equations converge to zero
as the second power of the lattice spacing, but that an average over local Regge equations
converges to zero as (at the very least) the third power of the lattice spacing. Numerical studies using analytic solutions to the Einstein equations show that these averages actually converge to zero as the fourth power of the lattice spacing.
14 pages, LaTeX, 8 figures mailed in separate file or email author directly. his work was partially supported by a Fellowship from Syracuse University and NSF ASC 93 18152 / PHY 93 18152 (ARPA supplemented).
https://surface.syr.edu/phy/16
oai:surface.syr.edu:phy-1020
2012-01-20T21:00:20Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Covariant Quantum Fields on Noncommutative Spacetimes
Balachandran, A. P.
Ibort, A.
Marmo, G.
Martone, M.
Working Paper
2010-01-01T08:00:00Z
High Energy Physics
General relativity and Quantum Cosmology
Mathematical physics
Quantum Algebra
Mathematics
Physics
<p>A spinless covariant field $\phi$ on Minkowski spacetime $\M^{d+1}$ obeys the relation $U(a,\Lambda)\phi(x)U(a,\Lambda)^{-1}=\phi(\Lambda x+a)$ where $(a,\Lambda)$ is an element of the Poincar\'e group $\Pg$ and $U:(a,\Lambda)\to U(a,\Lambda)$ is its unitary representation on quantum vector states. It expresses the fact that Poincar\'e transformations are being unitary implemented. It has a classical analogy where field covariance shows that Poincar\'e transformations are canonically implemented. Covariance is self-reproducing: products of covariant fields are covariant. We recall these properties and use them to formulate the notion of covariant quantum fields on noncommutative spacetimes. In this way all our earlier results on dressing, statistics, etc. for Moyal spacetimes are derived transparently. For the Voros algebra, covariance and the *-operation are in conflict so that there are no covariant Voros fields compatible with *, a result we found earlier. The notion of Drinfel'd twist underlying much of the preceding discussion is extended to discrete abelian and nonabelian groups such as the mapping class groups of topological geons. For twists involving nonabelian groups the emergent spacetimes are nonassociative.</p>
<p>20 pages, SU-4252-914</p>
https://surface.syr.edu/phy/20
oai:surface.syr.edu:phy-1019
2011-03-02T14:00:23Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Quantum Geons and Noncommutative Spacetimes
Balachandran, A. P.
Ibort, A.
Marmo, G.
Martone, M.
Working Paper
2010-01-01T08:00:00Z
High Energy Physics
General relativity and Quantum Cosmology
Mathematical physics
Quantum Algebra
Mathematics
Physics
<p>Physical considerations strongly indicate that spacetime at Planck scales is noncommutative. A popular model for such a spacetime is the Moyal plane. The Poincare group algebra acts on it with a Drinfel'd-twisted coproduct. But the latter is not appropriate for more complicated spacetimes such as those containing the Friedman-Sorkin (topological) geons. They have rich diffeomorphism groups and in particular mapping class groups, so that the statistics groups for N identical geons is strikingly different from the permutation group SN. We generalise the Drinfel'd twist to (essentially) generic groups including to finite and discrete ones and use it to modify the commutative spacetime algebras of geons as well to noncommutative algebras. The latter support twisted actions of diffeos of geon spacetimes and associated twisted statistics. The notion of covariant fields for geons is formulated and their twisted versions are constructed from their untwisted versions. Non-associative spacetime algebras arise naturally in our analysis. Physical consequences, such as the violation of Pauli principle, seem to be the outcomes of such nonassociativity. The richness of the statistics groups of identical geons comes from the nontrivial fundamental groups of their spatial slices. As discussed long ago, extended objects like rings and D-branes also have similar rich fundamental groups. This work is recalled and its relevance to the present quantum geon context is pointed out.</p>
<p>41 pages, SU-4252-902</p>
https://surface.syr.edu/phy/21
oai:surface.syr.edu:phy-1021
2012-09-05T16:00:07Z
publication:coscde
publication:dphy
publication:phy
publication:cas
S-waves and the Extraction of Beta_s
Stone, Sheldon
Presentation
2010-01-01T08:00:00Z
High Energy Physics
Phenomenology
Physics
<p>The CP Violating asymmetry in Bs mixing (beta_s) is one of the most promising measurements where physics beyond the Standard Model could be revealed. As such, analyses need to be subjected to great scrutiny. The mode Bs -> J/psi\phi has been used, and the mode Bs -> \phi \phi proposed for future measurements. These modes both have two vector particles in the final state and thus angular analyses must be used to disentangle the contributions from CP+ and CP- configurations. The angular distributions, however, could be distorted by the presence of S-waves masquerading as low mass K+K- pairs, that could result in erroneous values of beta_s. The S-waves could well be the result of a final state formed from an s-quark anti-s-quark pair in a 0+ spin-parity state, such as the f0(980) meson. Data driven and theoretical estimates of the Bs decay rate into the CP+ final state J/psi f0(980) are given, when f0 -> pi+pi-. The S-wave contribution in J\psi\phi should be taken into account when determining beta_s by including a K+K- S-wave amplitude in the fit. This may change the central value of current results and will also increase the statistical uncertainty. Importantly, the J/psi f0(980) mode has been suggested as an alternative channel for measuring beta_s.</p>
<p>Invited talk presented at Flavor Physics and CP Violation 2010, May 2010, Torino, Italy; to appear in proceedings. 6 pages 4 figures</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/22
oai:surface.syr.edu:phy-1022
2012-09-05T16:06:26Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Discreteness and the Transmission of Light from Distant Sources
Dowker, Fay
Henson, Joe
Sorkin, Rafael
Working Paper
2010-01-01T08:00:00Z
General Relativity and Quantum Cosmology
Physics
<p>We model the classical transmission of a massless scalar field from a source to a detector on a background causal set. The predictions do not differ significantly from those of the continuum. Thus, introducing an intrinsic inexactitude to lengths and durations - or more specifically, replacing the Lorentzian manifold with an underlying discrete structure - need not disrupt the usual dynamics of propagation.</p>
<p>6 pages, 1 figure</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/23
oai:surface.syr.edu:phy_etd-1028
2010-09-28T18:01:41Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Absolute branching fraction measurements and electron spectrum of inclusive charged and neutral D meson semileptonic decays
Redjimi, Radia
2005-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Marina Artuso
Branching fraction
Electron spectrum
Semileptonic decays
D mesons
CLEO
Physical Sciences and Mathematics
Physics
We present a measurement of the inclusive branching fractions for the decays D + [arrow right] Xe + ν e and D 0 [arrow right] X e + ν e , using 281 pb -1 of data collected on the ψ(3770) resonance with the CLEO-c detector. We find [Special characters omitted.] ( D 0 [arrow right] X e + ν e ) = (6.46 ± 0.17 ± 0.13)% and [Special characters omitted.] ( D + [arrow right] X e + ν e ) = (16.13 0.20 ± 0.33)%.
https://surface.syr.edu/phy_etd/30
oai:surface.syr.edu:phy_etd-1029
2010-09-28T18:12:41Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
A method for the study of anelasticity in fused silica
Kittelberger, Scott Erich
2005-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Peter R. Saulson
Anelasticity
Fused silica
Thermal noise
Damping
Condensed Matter Physics
Physical Sciences and Mathematics
Physics
Abstract Not Available.
https://surface.syr.edu/phy_etd/29
oai:surface.syr.edu:phy_etd-1030
2010-09-30T19:49:19Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Supertubes, black strings and D-brane systems
Cabrera Palmer, Belkis
2005-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Donald Marolf
Supertubes
Black strings
D-brane
String theory
Elementary Particles and Fields and String Theory
Physical Sciences and Mathematics
Physics
In this dissertation, we focus on aspects of String Theory and General Relativity. The study of objects of various spatial dimensions, or branes, have become an intrinsic part of modern String Theory. Here, we focus on three concrete topics concerning the physics of branes: supertubes, quantum D-brane polarization, and the stability of black branes. We devote the final part of this work to the study of fast travel in 3+1 dimensional spherically symmetric configurations.
https://surface.syr.edu/phy_etd/32
oai:surface.syr.edu:phy_etd-1031
2010-09-30T19:58:03Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
The accelerating universe and other cosmological aspects of modified gravity models
De Felice, Antonio
2005-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Mark Trodden
Accelerating universe
Gravity
Dark energy
Astrophysics and Astronomy
Physical Sciences and Mathematics
Physics
I give a short introduction to standard cosmology and a review of what it is meant by "the dark energy enigma" in chapter l. In chapter 2, I mention and describe some attempts found in the literature of the past few years to attack this problem. Dark energy candidates for which the equation-of-state parameter w is less than -1 violate the dominant energy condition. In scalar-tensor theories of gravity, however, the expansion of the universe can mimic the behavior of general relativity with w < -1 dark energy, without violating any energy conditions. I examine, in chapter 3, whether this possibility is phenomenologically viable by studying Brans-Dicke models and characterizing both the naturalness of the models themselves, and additional observational constraints from limits on the time-dependence of Newton's constant. I find that only highly contrived models would lead observers to measure w < -1. In chapter 4, I consider general curvature-invariant modifications of the Einstein-Hilbert action that become important only in regions of extremely low space-time curvature. I investigate the far future evolution of the universe in such models, examining the possibilities for cosmic acceleration and other ultimate destinies. The models generically possess de Sitter space as an unstable solution and exhibit an interesting set of attractor solutions which, in some cases, provide alternatives to dark energy models. In chapter 5, I study a baryogenesis mechanism operating in the context of hyperextended inflation and making use of a coupling between the scalar field and a standard model global current, such as B or B - L . The method is efficient at temperatures at which these currents are not conserved due to some higher dimensional operator. The particle physics and cosmological phenomenology are discussed. I consider constraints stemming from nucleosynthesis and solar system experiments.
https://surface.syr.edu/phy_etd/31
oai:surface.syr.edu:phy_etd-1032
2010-10-01T17:16:33Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
The nonlinear phototaxis signaling network of Chlamydomonas investigated by observing ciliary responses of individual cells to green and red light
Josef, Keith
2005-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Kenneth Foster
Green light
Phototaxis
Ciliary
Red light
Intracellular signaling
Chlamydomonas
Biochemistry, Biophysics, and Structural Biology
Biological and Chemical Physics
Biophysics
Cell and Developmental Biology
Life Sciences
Physical Sciences and Mathematics
Physics
The unicellular alga Chlamydomonas samples environmental conditions (light, chemical, temperature, touch, gravity) with multiple receptors. Sensory information is processed and integrated to control motion of its two cilia that propel the cell through its aquatic environment. The cell tracks light with green-light sensitive receptors concentrated in its eyespot and makes decisions to swim toward (positive phototaxis), away from (negative phototaxis), or orthogonal (diaphototaxis) to the light. The phototaxis signaling pathway was investigated by a holding single cell on a micropipette and illuminating its fixed photoreceptors while monitoring the ciliary motion. The cilia, beating in a planar "breast stroke" motion, were imaged on a quadrant photodiode array. Modulated green light stimulated the photoreceptors while detailed motion of each cilium was recorded over each beat cycle. Measures of ciliary responses determined from detector signals included beat frequency, stroke velocity, and relative phase or synchrony. Recordings from 302 individual cells were analyzed to investigate the phototaxis signaling network. Each measure displayed nonlinear response to green square-wave stimulation. Green light modulated by a pseudorandom noise pattern correlated with each measure produced linear and nonlinear response functions. This compact organization allows efficient response comparisons under various experimental conditions and with different mutants. Each measure has duration of a few hundred milliseconds; however each exhibits a unique delay, shape, and response sign. In addition, the two cilia respond differently. Modeling suggests a common signaling pathway for each measure from photoreceptor to cilia. Each cilium modifies the signal differently to provide phototaxis. Red light stimulates different photoreceptors than does green light, with different time scale responses. Long-period red-light step experiments show responses persisting for several seconds. Beat frequency increased with exponential saturation when red light is turned on and decreased exponentially when red light is turned off. Additionally, beat frequency undergoes a large amplitude transient decrease when red light is turned off. Results with simultaneous green and red light stimulation indicate that red light is involved in phototaxis direction decision-making. Single fixed-cell response modeling was extended to predict light modulation sensed by a free-swimming cell.
https://surface.syr.edu/phy_etd/38
oai:surface.syr.edu:phy_etd-1033
2010-10-01T18:33:35Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
A search for new physics at the TeV scale via a precise measurement of the weak mixing angle in Moller scattering
Emam, Waled S.
2004-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Paul Souder
Moller scattering
Parity violation
Weak mixing angle
Physical Sciences and Mathematics
Physics
This dissertation reports on a precise measurement of the parity-violating asymmetry in electron-electron (Møller) scattering at a four-momentum transfer Q 2 = 0.03 (GeV/c) 2 . The observed parity-violating asymmetry is A PV = -128 ± 14 (stat.) ± 12 (syst.) × 10 -9 . This is the most precise asymmetry ever measured in a parity-violating electron scattering. In the context of the Standard Model, the APB result determines the weak mixing angle, which is one of the fundamental parameters of the model. The result is sin 2 [Special characters omitted.] = 0.2403 ± 0.0014, which is consistent with the Standard Model expectation at the current level of precision. The comparison between this measurement of the weak mixing angle at low Q 2 and at the Z 0 pole establishes the running of sin 2 [straight theta] W with 6.5σ significance.
In addition, we report on the first observation of a transverse asymmetry in electron-electron scattering. The observed asymmetry is [Special characters omitted.] = 2.7 × 10 -6 , which is consistent with the theoretical predictions. We also provide a new measurement of the transverse asymmetry in ep scattering [Special characters omitted.] = 2 × 10 -6 .
The consistency of the result with the theoretical prediction provides new limits on the TeV scale physics. A limit of 0.9 TeV was set on the mass of the extra Z ' boson in the SO(10) Model. A limit of 14 TeV and 6 TeV was set on the compositeness scales [Special characters omitted.] and [Special characters omitted.] , respectively. Finally a limit of 0.2 TeV was set on ratio of the doubly-charged Higgs mass to the ee Δ coupling [Special characters omitted.] .
https://surface.syr.edu/phy_etd/37
oai:surface.syr.edu:phy_etd-1035
2010-10-01T19:44:49Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Laboratory simulations of chemical reactions on dust grains in the interstellar medium
Roser, Joseph E.
2004-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Gianfranco Vidali
Dust
Interstellar medium
Hydrogen
Carbon dioxide
Astrophysics and Astronomy
Physical Sciences and Mathematics
Physics
Dust grains exert a major influence upon the chemical composition of the interstellar medium: photoelectrons emitted from the dust grains are the primary energy source for heating interstellar gas, dust grains in dense molecular clouds can accumulate layers of frozen interstellar gases that participate in solid phase chemical reactions, and the most abundant molecule in the Universe, molecular hydrogen, primarily forms from hydrogen atoms adsorbed onto grain surfaces. Molecular hydrogen influences the evolution of molecular clouds by acting as a coolant during the gravitational collapse of the cloud and serving as a precursor for the formation of many molecular species. A complete description of molecular hydrogen formation in molecular clouds requires an understanding of the efficiency of hydrogen atom recombination on ice surfaces. Observations of interstellar carbon dioxide ice have the potential for serving as a diagnostic sign of the evolution of interstellar ice layers but require a satisfactory explanation of the formation mechanisms of interstellar CO 2 .
This work describes a series of investigations that were designed to study the properties of interstellar dust grains and to obtain and analyze data for astrophysically important chemical reactions. We measured the recombination efficiency of H atoms on the surface of amorphous H 2 O ices and measured the kinetics of H 2 formation and desorption on different morphologies of ice substrate. We demonstrated that the hydrogen atom recombination kinetics depend upon the morphology of the ice layer and that the recombination efficiency is consistent with observations of molecular clouds. We also demonstrated that CO and O can be trapped within an amorphous H 2 O ice layer at temperatures greater than their sublimation temperatures and that the reaction CO (ads) + O (ads) [arrow right] CO 2,(ads) can produce appreciable amounts of CO2 within an interstellar ice layer in the absence of ultraviolet or cosmic-ray irradiation of the ice mantles. Extensions of these experimental techniques for future investigations of chemistry on the surfaces of interstellar dust grain analogues are also discussed.
https://surface.syr.edu/phy_etd/35
oai:surface.syr.edu:phy_etd-1034
2010-10-01T19:28:42Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Explorations in fuzzy physics and non-commutative geometry
Kurkcuoglu, Seckin
2004-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
A. P. Balachandran
Fuzzy physics
Noncommutative geometry
Supersymmetry
Quantum field theories
Physical Sciences and Mathematics
Physics
Fuzzy spaces arise as discrete approximations to continuum manifolds. They are usually obtained through quantizing coadjoint orbits of compact Lie groups and they can be described in terms of finite-dimensional matrix algebras, which for large matrix sizes approximate the algebra of functions of the limiting continuum manifold. Their ability to exactly preserve the symmetries of their parent manifolds is especially appealing for physical applications. Quantum Field Theories are built over them as finite-dimensional matrix models preserving almost all the symmetries of their respective continuum models.
In this dissertation, we first focus our attention to the study of fuzzy supersymmetric spaces. In this regard, we obtain the fuzzy supersphere [Special characters omitted.] through quantizing the supersphere, and demonstrate that it has exact supersymmetry. We derive a finite series formula for the [low *]-product of functions over [Special characters omitted.] and analyze the differential geometric information encoded in this formula. Subsequently, we show that quantum field theories on [Special characters omitted.] are realized as finite-dimensional supermatrix models, and in particular we obtain the non-linear sigma model over the fuzzy supersphere by constructing the fuzzy supersymmetric extensions of a certain class of projectors. We show that this model too, is realized as a finite-dimensional supermatrix model with exact supersymmetry.
Next, we show that fuzzy spaces have a generalized Hopf algebra structure. By focusing on the fuzzy sphere, we establish that there is a [low *]-homomorphism from the group algebra SU (2)* of SU (2) to the fuzzy sphere. Using this and the canonical Hopf algebra structure of SU (2)* we show that both the fuzzy sphere and their direct sum are Hopf algebras. Using these results, we discuss processes in which a fuzzy sphere with angular momenta J splits into fuzzy spheres with angular momenta K and L .
Finally, we study the formulation of Chern-Simons (CS) theory on an infinite strip of the non-commutative plane. We develop a finite-dimensional matrix model, whose large size limit approximates the CS theory on the infinite strip, and show that there are edge observables in this model obeying a finite-dimensional Lie algebra, that resembles the Kac-Moody algebra.
https://surface.syr.edu/phy_etd/36
oai:surface.syr.edu:phy_etd-1036
2010-10-01T20:05:17Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Numerical studies of electron transport in disordered quantum dot arrays
Jha, Shantenu
2004-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
A. Alan Middleton
Electron transport
Quantum dot
Critical voltage
Capacitance disorder
Physical Sciences and Mathematics
Physics
Using analytical and numerical methods; we investigate transport of electrons, in a model of quantum clot arrays in the presence of impurities at zero temperature. The presence of disorder results in a critical voltage ( V T ) that must be exceeded before the array can conduct. We investigate the behavior of these arrays in three voltage regimes: below the critical voltage, at the critical voltage and above. Using a transfer-matrix style algorithm we compute the "first path" at V T and study both the structural properties and the current density profiles of this first path. Although just the first path can be studied using this approach, it helps understand the important energy and length scales. We find that the properties of the first conducting path are essentially unchanged in the presence of capacitative or tunneling resistance disorder to those in the presence of only a background charge disorder. We investigate the effects of capacitative disorder and tunneling resistance disorder in such arrays along with the random background potential. We find that the presence of a random background potential also dominates the qualitative behaviour above threshold; rather than capacitative or tunneling disorder. We use finite size scaling analysis and other statistical physics techniques to explore the nonlinear scaling of I-V about V T . We find that below V T , the presence of capacitative disorder introduces some changes. In spite of differences in the underlying microscopic details, we find that the dynamic I-V characteristics of arrays in the presence and absence of capacitance disorder are qualitatively similar.
https://surface.syr.edu/phy_etd/34
oai:surface.syr.edu:phy_etd-1037
2010-10-01T20:15:10Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Photon spectroscopy of heavy quarkonia
Muramatsu, Hajime
2004-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Tomasz Skwarnicki
Quarkonia
Branching ratios
Bottomonium
Physical Sciences and Mathematics
Physics
We have studied the inclusive photon spectrum in [Special characters omitted.] (2 S ), Υ(2 S ), and Υ(3 S ) decays using the CLEO III detector. We present the most precise measurements of electric dipole (E1) photon transition rates and photon energies for [Special characters omitted.] (2 S ) [arrow right] γχ cJ (1 P ), Υ(2 S ) [arrow right] γχ cJ (1 P ), and Υ(3 S ) [arrow right] γχ bJ (2 P ) ( J = 0, 1, 2). The rate for rare E1 transition, Υ(3 S ) [arrow right] γχ b0 (1 P ) is measured for the first time. We also confirm the hindered magnetic dipole (M1) transition, [Special characters omitted.] (2 S ) [arrow right] γη c (1 S ). However, the direct M1 transition [Special characters omitted.] (2 S ) [arrow right] γη c (2 S ) observed by the Crystal Ball as a narrow peak at a photon energy of 91 MeV is not found in our data.
We have also searched for the spin-singlet bottomonium states η b (1 S ) and η b (2 S ) via the hindered magnetic dipole (M1) photon transitions Υ(3 S ) [arrow right] γη b (1 S ), Υ(3 S ) [arrow right] γη b (2 S ); and Υ(2 S ) [arrow right] γη b (1 S ). No evidence for such transitions are found. We set upper limits on the branching ratios which rule out some of the theoretical calculations.
https://surface.syr.edu/phy_etd/33
oai:surface.syr.edu:phy-1024
2012-09-05T16:08:16Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Empirical Relations Between Static and Dynamic Exponents for Ising Model Cluster Algorithms
Coddington, Paul D.
Baillie, Clive F.
Article
1992-01-01T08:00:00Z
Autocorrelations
Swendsen-Wang cluster algorithm
Wolff cluster algorithm
Ising model
Physics
<p>We have measured the autocorrelations for the Swendsen-Wang and the Wolff cluster update algorithms for the Ising model in 2, 3 and 4 dimensions. The data for the Wolff algorithm suggest that the autocorrelations are linearly related to the specific heat, in which case the dynamic critical exponent zW int,E = α/ν. For the Swendsen-Wang algorithm, scaling the autocorrelations by the average maximum cluster size gives either a constant or a logarithm, which implies that zSW int,E = β/ν for the Ising model.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/25
oai:surface.syr.edu:phy-1025
2010-10-05T15:42:20Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Gravity And Electromagnetism In Noncommutative Geometry
Landi, Giovanni
Viet, Nguyen Ai
Wali, Kameshwar C.
Article
1994-01-01T08:00:00Z
Gravity
Electromagnetism
Z2 Noncommunicative differential calculus
Kaluza-Klein theory
Algebraic Geometry
Cosmology, Relativity, and Gravity
Electromagnetics and Photonics
Physics
We present a unified description of gravity and electromagnetism in the framework of a Z 2 non-commutative differential calculus. It can be considered as a “discrete version” of Kaluza-Klein theory, where the fifth continuous dimension is replaced by two discrete points. We derive an action which coincides with the dimensionally reduced one of the ordinary Kaluza-Klein theory.
https://surface.syr.edu/phy/26
oai:surface.syr.edu:phy-1026
2012-09-10T16:14:48Z
publication:coscde
publication:dphy
publication:phy
publication:cas
The Solution Space of the Unitary Matrix Model String Equation and the Sato Grassmannian
Anagnostopoulos, Konstantinos N.
Bowick, Mark
Schwarz, Albert
Article
1991-01-01T08:00:00Z
Symmetric unitary one-matrix model
String equation
Mathematics
Physics
<p>The space of all solutions to the string equation of the symmetric unitary one-matrix model is determined. It is shown that the string equation is equivalent to simple conditions on points V 1 and V 2 in the big cell Gr (0) of the Sato Grassmannian Gr. This is a consequence of a well-defined continuum limit in which the string equation has the simple form [P; Q \Gamma ] = 1, with P and Q \Gamma 2 \Theta 2 matrices of differential operators. These conditions on V 1 and V 2 yield a simple system of first order differential equations whose analysis determines the space of all solutions to the string equation. This geometric formulation leads directly to the Virasoro constraints L n (n 0), where L n annihilate the two modified-KdV -functions whose product gives the partition function of the Unitary Matrix Model.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/27
oai:surface.syr.edu:phy-1023
2012-09-10T15:47:13Z
publication:coscde
publication:dphy
publication:phy
publication:cas
An Operator Formalism for Unitary Matrix Models
Anagnostopoulos, Konstantinos N.
Bowick, Mark
Ishibashi, N.
Report
1991-01-01T08:00:00Z
double scaling limit
trigonometric orthogonal polynomials
Mathematics
<p>We analyze the double scaling limit of unitary matrix models in terms of trigonometric orthogonal polynomials on the circle. In particular we find a compact formulation of the string equation at the k th multicritical point in terms of pseudo-differential operators and a corresponding action principle. We also relate this approach to the mKdV hierarchy which appears in the analysis in terms of conventional orthogonal polynomials on the circle.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/24
oai:surface.syr.edu:phy_etd-1038
2010-10-05T19:42:10Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Upper limit for electron-positron decaying to neutral Lambda(baryon)-antineutral Lamba(baryon) cross section and R in the center-of-mass energy range from 11.230 to 11.382 GeV
Dorjkhaidav, Orlokh
2004-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Sheldon Stone
Electron-positron
Hadron
Cross section
Lambdab
Physical Sciences and Mathematics
Physics
We have searched for [Special characters omitted.] resonance production using data taking by CLEO III detector and set an upper limit for such a cross section to be on the order of 0.05-0.10 units of R in 95% confidence level in the scanning range at Center Mass of Energies from 11.230 to 11.382 GeV. The measurement of R = σ( e + e - [arrow right] hadrons)/σ( e + e - [arrow right] μ + μ - ) has been made in this scan range as well. The measured R value near Λ b threshold is R = 4.01 ± 0.15
https://surface.syr.edu/phy_etd/41
oai:surface.syr.edu:phy_etd-1039
2010-10-07T18:44:17Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
A measurement of parity-violating asymmetry with polarized electrons scattered from protons and implications for strange form factors
Tonguc, Baris Tamer
2003-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Paul A. Souder
Parity-violating
Asymmetry
Polarized electrons
Protons
Strange form factors
Physical Sciences and Mathematics
Physics
We have measured the parity violating asymmetry with polarized electrons scattered elastically from protons. The result is A = -15.05 ± 0.98( stat ) ± 0.56( syst ) ppm at the kinematic point [left angle bracket][straight theta] lab [right angle bracket] = 12.3° and [left angle bracket] Q 2 [right angle bracket] = 0.477( GeV/c ) 2 . The value for the linear combination of the strange form factors found using A is [Special characters omitted.] + 0.392[Special characters omitted.] = 0.025 ± 0.020 ± 0.014 where the first error is experimental and the second stems from the uncertainties in the electromagnetic form factors.
https://surface.syr.edu/phy_etd/40
oai:surface.syr.edu:phy_etd-1040
2010-10-07T20:34:23Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
First observation of the parity violating asymmetry in Moller scattering
Younus, Imran
2003-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Paul Souder
Parity violating asymmetry
Moller scattering
Calorimeter
Physical Sciences and Mathematics
Physics
This thesis reports on the E158 experiment at Stanford Linear Accelerator Center (SLAC), which has made the first observation of the parity non-conserving asymmetry in Moller scattering. Longitudinally polarized 48 GeV electrons are scattered off unpolarized (atomic) electrons in a liquid hydrogen target with an average Q 2 of 0.027 GeV 2 . The asymmetry in this process is proportional to (¼ - sin 2 [straight theta] W ), where sin 2 [straight theta] W gives the weak mixing angle.
The thesis describes the experiment in detail, with a particular focus on the design and construction of the electromagnetic calorimeter. This calorimeter was the primary detector in the experiment used to measure the flux of the scattered Moller electrons and eP electrons. It employed the quartz fiber calorimetey technique, and was built at Syracuse University.
The preliminary results from the first experimental data taken in spring 2002 give A PV = -151.9 ± 29.0( stat ) ± 32.5( syst ) parts per billion. This in turn gives sin 2 [straight theta] W = 0.2371 ± 0.0025 ± 0.0027, which is consistent with the Standard Model prediction (0.2386 ± 0.0006).
https://surface.syr.edu/phy_etd/39
oai:surface.syr.edu:phy_etd-1041
2010-10-11T13:22:10Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Lepton energy moments, operator product expansion and the CKM parameter matrix element, V(cb)
Boulahouache, Chaouki
2002-08-01T07:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Marina Artuso
Cabibbo-Kobayashi-Maskawa matrix
Lepton
Energy moments
Operator product expansion
Elementary Particles and Fields and String Theory
Physics
We have determined [Special characters omitted.] and [Special characters omitted.] from truncated moments of the lepton energy spectra for both e ± and μ ± . Combining both lepton species, we measured two lepton energy moments: [Special characters omitted.] = 0.6187 ± 0.0014 ± 0.0016 and [Special characters omitted.] = 1.7810 ± 0.0007 ± 0.0009. The extracted values for [Special characters omitted.] and [Special characters omitted.] through order 1/[Special characters omitted.] in the non-perturbative expansion and [Special characters omitted.] in the perturbative one in the MS scheme, are: [Special characters omitted.] = -0.25 ± 0.02 ± 0.05 ± 0.14 and [Special characters omitted.] = 0.39 ± 0.03 ± 0.06 ± 0.12, where the uncertainties are statistical, systematic and theoretical respectively. The theoretical expression needed to extract | V cb | from the measured semileptonic width is evaluated using these HQE parameters. Using the world average for the semileptonic width, we find: [Special characters omitted.] . Finally, the short range mass of the b-quark [Special characters omitted.] is evaluated and found to be 4.82 ± 0.07| exp ± 0.11| th .
https://surface.syr.edu/phy_etd/47
oai:surface.syr.edu:phy_etd-1042
2010-10-11T17:14:59Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Interface modulation spectroscopy and doping physics in amorphous silicon
Zhu, Kai
2003-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Eric A. Schiff
Interface modulation spectroscopy
Doping
Amorphous silicon
Solar cells
Physical Sciences and Mathematics
Physics
We have developed an interface-modulation spectroscopy that probes the optical spectra of dopants and defects at interface regions a few nanometers wide in semiconductor devices such as p-i-n diodes. The method involves detecting the modulation of the optical transmittance or reflectance of diodes due to modulation of the electrical space-charge accumulated near these interfaces. We have applied the method to diodes based on hydrogenated amorphous silicon (a-Si:H). The samples that we obtained varied widely in their doped, n-type and p-type layers.
The results are far more complex than expected in the context of the "standard" doping model for a-Si:H due to Street. In this standard model, only a small fraction of dopant atoms incorporated into a-Si:H are electronic donors (or acceptors), and such donors and acceptors are created in conjunction with compensating densities of dangling bond defects. This standard model predicts that the modulation spectra should be negative and nearly featureless for a broad range of optical energies less than the semiconductor bandgap (about l.75 eV for a-Si:H), and we do observe such spectra in several samples. In addition, we found an interesting, sharp (0.l eV wide) positive spectral line near 0.8 eV, which we believe is due to an internal optical transition of a dopant-defect complex incorporating a fourfold coordinated phosphorus and a dangling bond. For one series of samples with varying phosphorus-doping levels, this line was absent for doping levels below 0.5%, and was nearly fully developed for levels greater than 1.0%. This line was absent for other series of samples prepared by the same laboratory under somewhat different deposition conditions. These measurements suggest the possibility of a phase transition in the structure of phosphorus-doped a-Si:H for sufficiently large phosphorus concentrations.
https://surface.syr.edu/phy_etd/46
oai:surface.syr.edu:phy_etd-1043
2013-01-31T19:10:45Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Neutrinos in particle physics and cosmology
Nasri, Salah
2003-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Joseph Schechter
Joseph Schechter
Neutrinos
Particle physics
Cosmology
Fermions
Physical Sciences and Mathematics
Physics
<p>One of the outstanding problems in particle physics is the understanding of the origin of the fermion masses and mixings. In particular the explanation of the smallness of neutrino masses and the largeness of the mixing angles is of great importance. We propose a model for generating small Majorana neutrino masses at the TeV scale. The smallness of the neutrino masses in this model is not due to the largeness of the right handed neutrino mass, but to the smallness of the Dirac masses which are induced at the one loop level. The generation of the baryon asymmetry of the universe through the lepton asymmetry is also discussed within this model. The mixing angle in the leptonic sector is studied using triangular mass matrices for the charged leptons and the neutrinos. We found that the large mixing angles in both the atmospheric and solar neutrino anomalies can be obtained within these textures. Motivated by the unification of the b quark and the τ lepton in SO (10) we investigated the ansatz Tr M ν = 0. From the information of two neutrino squared mass differences and the leptonic mixing matrix one can reconstruct the neutrino mass matrix. Using the accurately known value of the Z width we investigated in detail the coupling of two neutrinos to the Majoron. Bounds on the coupling constants are obtained in both the "3 + 1" and "(3 + 1 + N )" dimensional case, with the Majoron free to travel in the N compact extra dimensions.</p>
https://surface.syr.edu/phy_etd/45
oai:surface.syr.edu:phy_etd-1044
2010-10-11T18:33:40Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Role of light scalar resonances in strongly interacting chiral effective Lagrangians
Abdel-Rehim, Abdou M.
2003-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Joseph Schechter
Mesons
Higgs mass
Scalar resonances
Chiral effective Lagrangians
Elementary Particles and Fields and String Theory
Nuclear
Physical Sciences and Mathematics
Physics
We studied the role of a putative nonet of light scalar mesons in the isospin violating decay η [arrow right] 3π. The framework is a non-linear chiral effective Lagrangian. The contributions from the scalars is found to enhance the result for the decay width by 15% at leading order. Due to cancellations among different scalar contributions, their effect is less than expected. A preliminary discussion of the related process η ' [arrow right] 3π is given. We apply the K-matrix unitarization method to the case of strongly coupled Higgs sector of the electro-weak theory. The complex pole position of the scattering amplitude of the Goldstone bosons are evaluated for the whole range of bare Higgs masses. We compare the unitarized amplitude obtained from the K-matrix to the Breit-Wigner shape for narrow resonances. We apply the same technique to study the effect of final state interactions in the gluon fusion process. Finally, the K-matrix unitarization is used to study the properties of the scalar resonances σ(550) and f 0 (980) in the framework of non-linear chiral Lagrangian. The physical mass and width of these resonances are determined from the pole position of the I = 0, J = 0 partial wave of the ππ scattering amplitude. It is found that, to a great extent, the results are very similar to those obtained in the framework of linear chiral Lagrangian unitarized by the K-matrix method or the nonlinear chiral Lagrangian approximately unitarized by a modified Breit-Wigner resonance shape. A discussion of the effect of σ(550) and f 0 (980) in the I = 1, J = 1 and I = 2, J = 0 partial waves, where the ρ(770) vector resonance dominates, is given.
https://surface.syr.edu/phy_etd/44
oai:surface.syr.edu:phy_etd-1045
2010-10-11T18:38:32Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Search for eta(b) in the CLEO-II Upsilon(3S) and Upsilon(2S) data
Bukin, Konstantin Vladimirovich
2003-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Towasz Skwarnicki
Upsilon meson
Eta mesons
Supersymmetry
Branching ratios
Elementary Particles and Fields and String Theory
Physical Sciences and Mathematics
Physics
We searched for η b via hindered M1 transitions Υ(3 S ) [arrow right] γη b and Υ(2 S ) [arrow right] γη b using CLEO-II data. No significant evidence for such transitions was found, and we set upper limits on the corresponding branching ratios that contradict many phenomenological estimates for the rates of these transitions.
https://surface.syr.edu/phy_etd/43
oai:surface.syr.edu:phy_etd-1046
2010-10-11T19:08:03Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Supersymmetric theories on the lattice
Karamov, Sergey Alexandrovich
2003-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Simon Catterall
Lattice
Supersymmetry
Wess-Zumino models
Fermions
Physical Sciences and Mathematics
Physics
Both theoretical and computational aspects involved in non-perturbative studies of supersymmetric field theories are discussed. Specifically this thesis focuses on Wess-Zumino models in one and two dimensions. In two of the three models considered a lattice action which preserves an exact supersymmetry may be derived. In the third case no such action is possible, nevertheless a lattice theory can be written down which preserves supersymmetry at the quantum level to all orders in perturbation theory in the limit of vanishing lattice spacing. Dynamical fermion simulations are carried out using improved algorithms for all these models and the numerical results for mass spectra and Ward identities compared with theoretical expectations. For the third case evidence for spontaneous supersymmetry breaking via tunneling effects in finite volumes is presented.
https://surface.syr.edu/phy_etd/42
oai:surface.syr.edu:phy_etd-1047
2010-10-12T13:20:18Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Optical switching and memory using tungsten oxide
Osman, Joseph Michael
2002-05-01T07:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Joseph Chaiken
Photochromic
Electrochromic
Optical switching
Tungsten oxide
Optical memory
Atomic, Molecular and Optical Physics
In order to develop optical switches for optical computing, we searched for a candidate optically nonlinear material system that could be optimized for use in the fabrication of a nonlinear interface optical switch (NIOS). We chose thin films of tungsten oxide clusters. While experimentally verifying the optical nonlinearity of tungsten oxide cluster films, we discovered a latching color transition of WO 3 powder from yellow to blue using two wavelengths of light, one blue-green and one infrared. We then experimentally verified the yellow to blue color transition and determined how to recover the yellow state from the blue state using a single infrared wavelength. We used this knowledge to develop a photochromic optical memory system. We explored the optical power dependence of the photochromic process. These studies led us to believe that the writing process involves electronic transitions due to the blue-green wavelength and thermal softening of the lattice due to the infrared wavelength. This leads to reduction of the yellow media during the subsequent cooling into a substoichiometric blue state. This change of state is a latching process, as the blue state remains until it is erased. The erase process involves heating of the medium in contact with O 2 or some other oxidant to return it to the thermodynamic ground state of the tungsten-oxygen system, yellow WO 3 . The NIOS concept was then combined with the results of our new understanding of the photochromism of tungsten oxide to produce latching optical switches.
https://surface.syr.edu/phy_etd/49
oai:surface.syr.edu:phy-1027
2012-12-11T17:08:33Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Exact Lattice Supersymmetry: the Two-Dimensional N = 2 Wess-Zumino Model
Catterall, Simon
Karamov, Sergey
Article
2008-01-01T08:00:00Z
High Energy Physics Lattice
High Energy Physics Theory
Physics
<p>We study the two-dimensional Wess-Zumino model with extended N = 2 supersymmetry on the lattice. The lattice prescription we choose has the merit of preserving exactly a single supersymmetric invariance at finite lattice spacing a. Furthermore, we construct three other transformations of the lattice fields under which the variation of the lattice action vanishes to O(ga2) where g is a typical interaction coupling. These four transformations correspond to the two Majorana supercharges of the continuum theory. We also derive lattice Ward identities corresponding to these exact and approximate symmetries. We use dynamical fermion simulations to check the equality of the massgaps in the boson and fermion sectors and to check the lattice Ward identities. At least for weak coupling we see no problems associated with a lack of reflection positivity in the lattice action and findgood agreement with theory. At strong coupling we provide evidence that problems associated with a lack of reflection positivity are evaded for small enough lattice spacing.</p>
<p>SU-4252-735, Journal reference: Phys.Rev. D65 (2002) 094501 DOI: 10.1103/PhysRevD.65.094501 Cite as: arXiv:hep-lat/0108024v2</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/29
oai:surface.syr.edu:phy-1028
2012-12-11T17:11:04Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Supersymmetric Lattices - a Brief Introduction
Catterall, Simon
Article
2009-01-01T08:00:00Z
Lattice
High Energy Physics
Physics
<p>Recently, new theoretical ideas have allowed the construction of lattice actions which are explicitly invariant under one or more supersymmetries. These theories are local and free of doublers and in the case of Yang-Mills theories also possess exact gauge invariance. In this talk these ideas are reviewed with particular emphasis being placed on ${\cal N}=4$ super Yang-Mills theory.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/28
oai:surface.syr.edu:phy_etd-1048
2013-01-24T19:15:14Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Critical behavior of spin models on fluctuating bounded geometries
McGuire, Scott V.
2001-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Simon Catterall
Critical behavior
Spin
Fluctuating bounded geometries
Quantum gravity
Triangulation
Physical Sciences and Mathematics
Physics
<p>This dissertation describes the use of Monte Carlo simulations to study systems consisting of simple matter fields coupled to 2-d quantum gravity. Explicitly, we have studied Ising spins in interaction with a discrete triangulated geometry with the topology of a disk. Two classes of lattice model were examined; in the first the Ising spins were placed on the vertices of the triangulation and in the second they were associated with centers of triangles. In both cases we have utilized an Ising action which contains a boundary magnetic field. For the case of Ising spins on the vertices and zero boundary magnetic field, it is shown that the model possesses three phases. For one of these the boundary length grows linearly with disk area while the other two phases are characterized by a boundary length on the order of the cut-off. A line of continuous magnetic transitions separates the two small boundary phases. The critical exponents of the continuous magnetic phase transition are determined and related to predictions from continuum 2-d quantum gravity. This line of continuous transitions terminates on a line of discontinuous phase transitions dividing the small boundary phases from the large boundary phase. The scaling of bulk magnetization and boundary magnetization as a function of boundary magnetic field in the vicinity of this tricritical point are examined. The corresponding tricritical point for the model with Ising spins on the triangles is found. The scaling of bulk magnetization and boundary magnetization as a function of boundary magnetic field in the vicinity of this tricritical point are examined as well. We discuss the results in the context of universality of lattice models.</p>
https://surface.syr.edu/phy_etd/48
oai:surface.syr.edu:phy_etd-1049
2010-10-13T13:27:40Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Statistical mechanics of self-avoiding crystalline membranes and topological defect formation
Cacciuto, Angelo
2002-06-01T07:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Mark J. Bowick
Cosmology
Self-avoiding
Crystalline membranes
Defect formation
Condensed Matter Physics
Elementary Particles and Fields and String Theory
Physics
This thesis investigates two important topics in modern statistical mechanics. The first three chapters are devoted to the statistical mechanics of random surfaces. We present an analysis of extensive large-scale Monte Carlo simulations of Self-avoiding fixed-connectivity membranes for sizes (number of faces) ranging from 512 to 17672 (triangular) plaquettes. Self-avoidance is implemented via impenetrable plaquettes . We simulate the impenetrable plaquettes model in both three and four bulk dimensions. In both cases we find the membrane to be flat for all temperatures: The size exponent in three dimensions is ν = 0.95(5). The single flat phase appears, furthermore, to be equivalent to the large bending rigidity phase of phantom membranes; the roughness exponent in three dimensions is ζ = 0.63(4) and its Poisson ratio σ = -0.37(6). These results suggest that there is a unique universality class for flat crystalline membranes without attractive interaction. The last chapter deals with the Formation and Dynamics of Topological Strings in a U(1) Linear Sigma model in three spatial dimensions. For over-damped Langevin dynamics we find that defect production is suppressed by an interaction between correlated domains that reduce the effective spatial variation of the phase of the order field. The degree of suppression is sensitive to the quench rate. A detailed description of the numerical methods used to analyze the model is reported.
https://surface.syr.edu/phy_etd/50
oai:surface.syr.edu:phy_etd-1050
2010-10-15T12:33:32Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Thermal noise in low loss flexures
Gretarsson, Andri Marcus
2002-06-01T07:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Peter R. Saulson
Flexures
Fused silica fibers
Gravitational waves
Thermal noise
Astrophysics and Astronomy
Physics
Flexures with low mechanical noise are needed in several types of experiment. This dissertation presents a study of the fundamental sources of mechanical noise in flexures at room temperature. Fused silica fibers are perhaps the lowest noise flexure currently avail able, and thermal noise in fused silica fibers is given the largest emphasis. The dissertation has three main sections: (1) Description of a simple sensor capable of monitoring excitations of a thin flexure at the level of thermal noise. The sensor is used to verify the theoretical prediction for the level of thermal noise, and to search for fundamental sources of non-thermal noise occurring in tungsten and fused silica fibers under different loads. (2) Record of measurements of intrinsic dissipation in fused silica fibers as a function of fiber diameter and mode frequency. The results show that in fused silica fibers of diameter less than about 1 mm, most of the loss occurs at the fiber surface. (3) Application of the results of the previous sections to the prediction of thermal noise in advanced interferometric gravitational wave detectors. Thermal noise from the surfaces of fused silica fibers suspending the test masses of such detectors provides a small but not insignificant contribution to the overall noise budget. Application of the formalism developed to treat surface loss in fibers to recent theoretical and experimental results indicates that the loss associated with the reflective optical coatings on the test mass faces may seriously limit the astronomical reach of future gravitational wave detectors.
https://surface.syr.edu/phy_etd/53
oai:surface.syr.edu:phy_etd-1051
2010-10-15T15:08:04Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
A measurement of the strange quark content of the proton
Kahl, William Edward
2000-02-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Paul A. Souder
Strange quark
Proton
Parity-violating
Weak neutral current
Atomic, Molecular and Optical Physics
Elementary Particles and Fields and String Theory
Physics
We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from the proton. The kinematic point [[left angle bracket][straight theta] lab [right angle bracket] = 0.48( GeV / c ) 2 ] is chosen to provide sensitivity, at a level that is of theoretical interest, to the strange electric form factor [Special characters omitted.] The result, A = -14.5 ± 2.2 ppm, is consistent with the electroweak standard model and no additional contributions from strange quarks. In particular, the measurement implies [Special characters omitted.] + 0.39[Special characters omitted.] = 0.023 ± 0.034(stat) ± 0.026([Special characters omitted.] ), where the last uncertainty arises from the estimated uncertainty in the neutron electric form factor.
https://surface.syr.edu/phy_etd/52
oai:surface.syr.edu:phy-1029
2012-09-21T15:42:30Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Plasmonic Light-trapping and Quantum Efficiency Measurements on Nanocrystalline Silicon Solar Cells and Silicon-On-Insulator Devices
Schiff, Eric A
Zhao, Hui
Ozturk, Birol
Yan, Baojie
Yang, Jeff
Conference Document
2010-01-01T08:00:00Z
Plasmonic Light-trapping
Nanocrystalline Silicon Solar Cells
Physics
<p>Quantum efficiency measurements in nanocrystalline silicon (nc-Si:H)solar cells deposited onto textured substrates indicate that these cells are close to the "stochastic lighttrapping limit" proposed by Yablonovitch in the 1980s. An interesting alternative to texturing is "plasmonic" light-trapping based on non-textured cells and using an overlayer of metallic nanoparticles to produce light-trapping. While this type of light-trapping has not yet been demonstrated for nc-Si:H solar cells, significant photocurrent enhancements have been reported on silicon-on-insulator devices with similar optical properties to nc-Si:H. Here we report our measurements of quantum efficiencies in nc-Si:H solar cells and normalized photoconductance spectra in SOI photodetectors with and without silver nanoparticle layers. As was done previously, the silver nanoparticles were created by thermal annealing of evaporated silver thin films. We observed enhancement in the normalized photoconductance spectra of SOI photodetectors at longer wavelengths with the silver nanoparticles. For nc-Si:H solar cells, we have not yet observed significant improvement of the quantum efficiency with the addition of annealed silver films.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/30
oai:surface.syr.edu:phy_etd-1052
2010-10-15T18:06:08Z
publication:coscde
publication:dphy
publication:phy_etd
publication:phy
publication:etd
publication:cas
Dynamics of causal sets
Rideout, David Porter
2001-01-01T08:00:00Z
Dissertation
Doctor of Philosophy (PhD)
Physics
Rafael D. Sorkin
Causal sets
Quantum gravity
Random graph theory
Physical Sciences and Mathematics
Physics
The Causal Set approach to quantum gravity asserts that spacetime, at its smallest length scale, has a discrete structure. This discrete structure takes the form of a locally finite order relation, where the order, corresponding with the macroscopic notion of spacetime causality, is taken to be a fundamental aspect of nature.
After an introduction to the Causal Set approach, this thesis considers a simple toy dynamics for causal sets. Numerical simulations of the model provide evidence for the existence of a continuum limit. While studying this toy dynamics, a picture arises of how the dynamics can be generalized in such a way that the theory could hope to produce more physically realistic causal sets. By thinking in terms of a stochastic growth process, and positing some fundamental principles, we are led almost uniquely to a family of dynamical laws (stochastic processes) parameterized by a countable sequence of coupling constants. This result is quite promising in that we now know how to speak of dynamics for a theory with discrete time. In addition, these dynamics can be expressed in terms of state models of Ising spins living on the relations of the causal set, which indicates how non-gravitational matter may arise from the theory without having to be built in at the fundamental level.
These results are encouraging in that there exists a natural way to transform this classical theory, which is expressed in terms of a probability measure, to a quantum theory, expressed in terms of a quantum measure. A sketch as to how one might proceed in doing this is provided. Thus there is good reason to expect that Causal Sets are close to providing a background independent theory of quantum gravity.
https://surface.syr.edu/phy_etd/51
oai:surface.syr.edu:phy-1030
2012-09-05T16:21:17Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Transit Time Measurements of Charge Carriers in Disordered Silicons: Amorphous, Nanocrystalline, and Nanoporous
Schiff, Eric A
Article
2009-01-01T08:00:00Z
a-Si:H; microcrystalline silicon; mobility; porous silicon
Physics
<p>We summarize published hole transit-time measurements for hydrogenated amorphous silicon, microcrystalline silicon, and light-emitting nanoporous silicon in terms of drift mobilities and dispersion parameters. For amorphous and microcrystalline silicon, the anomalously dispersive measurements are broadly consistent with multiple-trapping by bandtail traps with an exponential distribution of energy depths. One unexplained result has been that the trap emission prefactor frequency is about 1000 times smaller in microcrystalline silicon than in amorphous silicon. We present a model incorporating both detailed-balance effects and a previously proposed Meyer–Neldel variation of with trap-depth; the model accounts for the factor 1000. We discuss general trap distributions incorporating variations of both trap depth and prefactor frequency; a model for which dispersion is due entirely to prefactor variation accounts for measurements on nanoporous silicon.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/31
oai:surface.syr.edu:phy-1032
2012-11-28T16:04:07Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Hole Drift Mobility Measurements on a-Si:H using Surface and Uniformly Absorbed Illumination
Dinca, Steluta A.
Schiff, Eric A
Guha, S.
Yan, Baojie
Yang, Jeff
Conference Document
2009-01-01T08:00:00Z
Disordered solids
Photoconduction and photovoltaic effects
Charge carriers: generation
recombination
lifetime
and trapping
Physics
<p>The standard, time-of-flight method for measuring drift mobilities in semiconductors uses strongly absorbed illumination to create a sheet of photocarriers near an electrode interface. This method is problematic for solar cells deposited onto opaque substrates, and in particular cannot be used for hole photocarriers in hydrogenated amorphous silicon (a-Si:H) solar cells using stainless steel substrates. In this paper we report on the extension of the time-of-flight method that uses weakly absorbed illumination. We measured hole drift-mobilities on seven a-Si:H nip solar cells using strongly and weakly absorbed illumination incident through the n-layer. For thinner devices from two laboratories, the drift-mobilities agreed with each other to within a random error of about 15%. For thicker devices from United Solar, the driftmobilities were about twice as large when measured using strongly absorbed illumination. We propose that this effect is due to a mobility profile in the intrinsic absorber layer in which the mobility decreases for increasing distance from the substrate.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/33
oai:surface.syr.edu:phy-1031
2012-09-05T16:24:16Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Solvent-Washable Polymer Templated Synthesis of Mesoporous Materials and Solic-Acid Nanocatalysts in One-Pot
Mishler, Richard E., II
Biradar, Ankush V.
Duncan, Cole T.
Schiff, Eric A
Asefa, Tewodros
Article
2009-01-01T08:00:00Z
mesoporous silica
Physics
<p>We report a new and simple one-pot synthetic method to produce mesoporous silica and nanoporous solid acid catalyst capable of catalyzing pinacole-pinacolone rearrangement and esterification reactions, by preparing a solvent washable phosphonated triblock copolymer template and self-assembling it in the presence of alkoxysilane.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/32
oai:surface.syr.edu:phy-1033
2012-09-05T16:25:38Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Carrier Drift-Mobilities and Solar Cell Models for Amorphous and Nanocrystalline Silicon
Schiff, Eric A
Conference Document
2009-01-01T08:00:00Z
amorphous silicon
nanocrystalline silicon
Physics
<p>Hole drift mobilities in hydrogenated amorphous silicon (a-Si:H) and nanocrystalline silicon (nc-Si:H) are in the range of 10-3 to 1 cm2/Vs at room-temperature. These low drift mobilities establish corresponding hole mobility limits to the power generation and useful thicknesses of the solar cells. The properties of as-deposited a-Si:H nip solar cells are quite close to their hole mobility limit, but the corresponding limit has not been examined for nc-Si:H solar cells. We explore the predictions for nc-Si:H solar cells based on parameters and values estimated from hole drift-mobility and related measurements. The indicate that the hole mobility limit for nc-Si:H cells corresponds to an optimum intrinsic-layer thickness of 2-3 2m, whereas the best nc-Si:H solar cells (10% conversion efficiency) have thicknesses around 2 2m.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/34
oai:surface.syr.edu:phy-1034
2012-09-05T16:27:49Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Polyaniline on Crystalline Silicon Heterojunction Solar Cells
Wang, Weining
Schiff, Eric A
Article
2007-01-01T08:00:00Z
solar cells
Physics
<p>Organic/inorganic heterojunction solar cells were fabricated on the (100) face of n-type silicon crystals using acid-doped polyaniline PANI with widely varying conductivities. For films with conductivities below 10−1 S/cm, the open-circuit voltage VOC increases with increasing film conductivity as expected when VOC is limited by the work function of the film. Extrapolation of these results to the higher conductivity films indicates that PANI could support VOC of 0.7 V or larger. VOC measurements for the cells with higher conductivity PANI saturated at 0.51 V. We speculate that uncontrolled surface states at the PANI/Si interface are reducing these values.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/35
oai:surface.syr.edu:phy-1035
2012-09-07T13:28:41Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Hole Mobilities and the Physics of Amorphous Silicon Solar Cells
Schiff, Eric A.
Article
2006-01-01T08:00:00Z
Silicon
Solar cells
Conductivity
Physics
<p>The effects of low hole mobilities in the intrinsic layer of pin solar cells are illustrated using general computer modeling; in these models electron mobilities are assumed to be much larger than hole values. The models reveal that a low hole mobility can be the most important photocarrier transport parameter in determining the output power of the cell, and that the effects of recombination parameters are much weaker. Recent hole drift-mobility measurements in a-Si:H are compared. While hole drift mobilities in intrinsic a-Si:H are now up to tenfold larger than two decades ago, even with recent materials a-Si:H cells are low-mobility cells. Computer modeling of solar cells with parameters that are consistent with drift-mobility measurements give a good account for the published initial power output of cells from United Solar Ovonic Corp.; deep levels (dangling bonds) in the intrinsic layer were not included in this calculation. Light-soaking creates a sufficient density of dangling bonds to lower the power from cells below the mobility limit, but in contemporary a-Si:H solar cells degradation is not large. We discuss the speculation that light-soaking is ‘self-limiting’ in such cells.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/36
oai:surface.syr.edu:phy-1036
2012-09-21T15:43:08Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Hole Mobility Limit of Amorphous Silicon Solar Cells
Liang, Jiang
Schiff, Eric A
Guha, S.
Yan, Baojie
Yang, Jeff
Article
2006-01-01T08:00:00Z
amorphous silicon
solar cells
Physics
<p>We present temperature-dependent measurements and modeling for a thickness series of hydrogenated amorphous silicon nip solar cells. The comparison indicates that the maximum power density (PMAX) from the as-deposited cells has achieved the hole-mobility limit established by valence bandtail trapping, and PMAX is thus not significantly limited by intrinsic-layer dangling bonds or by the doped layers and interfaces. Measurements of the temperature-dependent properties of light-soaked cells show that the properties of as-deposited and light-soaked cells converge below 250 K; a model perturbing the valence band tail traps with a density of dangling bonds accounts adequately for the convergence effect.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/37
oai:surface.syr.edu:phy-1040
2012-09-07T13:48:54Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Conducting Polymer and Hydrogenated Amorphous Silicon Hybrid Solar Cells
Williams, Evan L.
Jabbour, Ghassan E.
Wang, Qi
Shaheen, Sean E.
Schiff, Eric A
Article
2005-01-01T08:00:00Z
solar cells
Physics
<p>An organic-inorganic hybrid solar cell with a p-i-n stack structure has been investigated. The p-layer was a spin coated film of PEDOT:PSS poly 3,4-ethylenedioxythiophene polystyrenesulfonate. The i-layer was hydrogenated amorphous silicon a-Si:H, and the n-layer was microcrystalline silicon c-Si. The inorganic layers were deposited on top of the organic layer by the hot-wire chemical vapor deposition technique at 200 °C. These hybrid devices exhibited open circuit voltages VOC as large as 0.88 V and solar conversion efficiencies as large as 2.1%. Comparison of these devices with those incorporating a-SiC:H:B p-layers indicates that the organic layer is acting as an electrically ideal p-layer.</p>
<p>First author and SU author listed for additional authors see the article.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/41
oai:surface.syr.edu:phy-1038
2012-09-07T13:44:45Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Hole Drift-Mobility Measurements in Microcrystalline Silicon
Dylla, T.
Finger, F.
Schiff, Eric A
Article
2005-01-01T08:00:00Z
microcrystalline silicon
photocurrents
Physics
<p>We have measured transient photocurrents on several p-i-n solar cells based on microcrystalline silicon. For two of these samples, we were able to obtain conclusive hole drift-mobility measurements. Despite the predominant crystallinity of these samples, temperature-dependent measurements were consistent with an exponential-bandtail trapping model for transport, which is usually associated with noncrystalline materials. We estimated valence bandtail widths of about 31 meV and hole band mobilities of 1–2 cm2 /V s. The measurements support mobility-edge transport for holes in these microcrystalline materials, and broaden the range of materials for which mobility-edge transport corresponds to an apparently universal band mobility of order 1 cm2/V s.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/39
oai:surface.syr.edu:phy-1044
2010-10-16T23:31:03Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Hole Drift-Mobility Measurements and Multiple-Trapping in Microcrystalline Silicon
Dylla, T.
Finger, F.
Schiff, Eric A
Conference Document
2004-01-01T08:00:00Z
microcrystalline silicon
Physics
We present photocarrier time-of-flight measurements of the hole drift-mobility in
microcrystalline silicon samples with a high crystalline volume fraction; typical roomtemperature
values are about 1 cm2/Vs. Temperature-dependent measurements are consistent
with the model of multiple-trapping in an exponential bandtail. While this model has often been
applied to amorphous silicon, its success for predominantly crystalline samples is unexpected.
The valence bandtail width is 31 meV, which is about 10-20 meV smaller than values reported
for a-Si:H, and presumably reflects the greater order in the microcrystalline material. The hole
band-mobility is about 1 cm2/Vs – essentially the same magnitude as has been reported for
electrons and for holes in amorphous silicon, and suggesting that this magnitude is a basic
characteristic of mobility-edges, at least in silicon-based materials. The attempt-frequency υ is
about 109 s-1; this value is substantially smaller than the values 1011 - 1012 s-1 typically reported
for holes in amorphous silicon, but the physical significance of the parameter remains obscure.
https://surface.syr.edu/phy/45
oai:surface.syr.edu:phy-1045
2012-09-07T13:56:42Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Low-Mobility Solar Cells: a Device Physics Primer with Application to Amorphous Silicon
Schiff, Eric A
Article
2003-01-01T08:00:00Z
amorphous silicon
Physics
<p>The properties of pin solar cells based on photogeneration of charge carriers into lowmobility materials were calculated for two models. Ideal p- and n-type electrode layers were assumed in both cases. The first, elementary case involves only band mobilities and direct electron–hole recombination. An analytical approximation indicates that the power in thick cells rises as the 1 4 power of the lower band mobility, which reflects the buildup of space-charge under illumination. The approximation agrees well with computer simulation. The second model includes exponential bandtail trapping, which is commonly invoked to account for very low hole drift mobilities in amorphous silicon and other amorphous semiconductors. The two models have similar qualitative behavior. Predictions for the solar conversion efficiency of amorphous silicon-based cells that are limited by valence bandtail trapping are presented. The predictions account adequately for the efficiencies of present a-Si :H cells in their ‘‘asprepared’’ state (without light-soaking), and indicate the improvement that may be expected if hole drift mobilities (and valence bandtail widths) can be improved.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/46
oai:surface.syr.edu:phy-1042
2012-11-28T16:02:10Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Temperature-Dependent Open-Circuit Voltage Measurements and Light-Soaking in Hydrogenated Amorphous Silcon Solar Cells
Liang, Jianjun
Schiff, Eric A
Guha, S.
Yan, Baojie
Yang, Jeff
Conference Document
2005-01-01T08:00:00Z
amorphous silicon
solar cells
Physics
<p>We present temperature-dependent measurements of the open-circuit voltage VOC(T) in hydrogenated amorphous silicon nip solar cells prepared at United Solar. At room-temperature and above, VOC measured using near-solar illumination intensity differs by as much as 0.04 V for the as-deposited and light-soaked states; the values of VOC for the two states converge below 250 K. Models for VOC based entirely on recombination through deep levels (dangling bonds) do not account for the convergence effect. The convergence is present in a model that assumes the recombination traffic in the as-deposited state involves only bandtails, but which splits the recombination traffic fairly evenly between bandtails and defects for the light-soaked state at room-temperature. Recombination mechanisms are important in understanding light-soaking, and the present results are inconsistent with at least one well-known model for defect generation.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/43
oai:surface.syr.edu:phy-1039
2012-11-28T16:01:41Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Light-Soaking Effects on the Open-Circuit Voltage of a-Si:H Solar Cells
Liang, Jianjun
Schiff, Eric A
Guha, S.
Yan, Baojie
Yang, J.
Conference Document
2005-01-01T08:00:00Z
solar cells
Physics
<p>We present measurements on the decline of the open-circuit voltage VOC in a-Si:H solar cells during extended illumination (light-soaking) at 295 K. We used a near-infrared laser that was nearly uniformly absorbed in the intrinsic layer of the cell. At the highest photogeneration rate (about 2x1021 cm-3), a noticeable decline (0.01 V) occurred within about 10 minutes; VOC stabilized at 0.04 V below its initial value after about 200 hours. We found that both the kinetics and the magnitudes of VOC are reasonably consistent with the predictions of a calculation combining a bandtail+defect picture for recombination and a hydrogen-collision model for defect generation. The version of the hydrogen-collision model that we used assumes that only bandtail recombination drives the hydrogen collision processes. Within this picture, the crossover between bandtail and defect recombination occurs on the same timescale as the “light-induced annealing” process that accounts for stabilization of the optoelectronic properties for long lightsoaking times.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/40
oai:surface.syr.edu:phy-1041
2012-09-07T13:51:57Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Temperature Dependence of the Electron Diffusion Coefficient in Electrolyte-Filled TiO2 Nanoparticle Films: Evidence Against Multiple Trapping in Exponential Conduction-Band Tails
Kopidakis, Nikos
Benkstein, Kurt D.
van de Lagemaat, Jao
Yuan, Quan
Schiff, Eric A
Article
2006-01-01T08:00:00Z
Nanocrystalline materials
Photoconduction and photovoltaic effects
Disordered solids
Physics
<p>The temperature and photoexcitation density dependences of the electron transport dynamics in electrolytefilled mesoporous TiO2 nanoparticle films were investigated by transient photocurrent measurements. The thermal activation energy of the diffusion coefficient of photogenerated electrons ranged from 0.19–0.27 eV, depending on the specific sample studied. The diffusion coefficient also depends strongly on the photoexcitation density; however, the activation energy has little, if any, dependence on the photoexcitation density. The light intensity dependence can be used to infer temperature-independent dispersion parameters in the range 0.3–0.5. These results are inconsistent with the widely used transport model that assumes multiple trapping of electrons in an exponential conduction-band tail. We can also exclude a model allowing for widening of a band tail with increased temperature. Our results suggest that structural, not energetic, disorder limits electron transport in mesoporous TiO2. The analogy between this material and others in which charge transport is limited by structural disorder is discussed.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/42
oai:surface.syr.edu:phy-1043
2012-09-07T13:55:30Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Drift-Mobility Measurements and Mobility Edges in Disordered Silicons
Schiff, Eric A
Article
2004-01-01T08:00:00Z
disordered silicons
Physics
<p>Published electron and hole drift-mobility measurements in hydrogenated amorphous silicon (a-Si:H), amorphous silicon alloys (a-SiGe:H and a-SiC:H), and microcrystalline silicon (μc-Si:H) are analysed in terms of the exponential bandtail trapping model. A three-parameter model was employed using an exponential bandtail width E, the band mobility μ0, and the attempt-toescape frequency ν. Low-temperature measurements indicate a value around μ0 = 1 cm2 V−1 s−1 for both the conduction and valence bands over the entire range of materials. High temperature-measurements for electrons in a-Si:H suggest a larger value of 7 cm2 V−1 s−1. These properties and those of the frequency ν are discussed as possible attributes of a mobility edge.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/44
oai:surface.syr.edu:phy-1047
2012-09-07T13:58:27Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Hole Drift-Mobility Measurements in Contemporary Amorphous Silicon
Dinca, S.
Schiff, Eric A
Vlahos, V.
Wronski, C. R.
Yuan, Q.
Conference Document
2003-01-01T08:00:00Z
amorphous silicon
Physics
<p>We present hole drift-mobility measurements on hydrogenated amorphous silicon from several laboratories. These temperature-dependent measurements show significant variations of the hole mobility for the differing samples. Under standard conditions (displacement/field ratio of 2×10-9 cm2/V), hole mobilities reach values as large as 0.01 cm2/Vs at room-temperature; these values are improved about tenfold over drift-mobilities of materials made a decade or so ago. The improvement is due partly to narrowing of the exponential bandtail of the valence band, but there is presently little other insight into how deposition procedures affect the hole drift-mobility.</p>
<p>First author and SU authors listed for additional authors see the article.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/48
oai:surface.syr.edu:phy-1037
2012-09-07T13:43:19Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Temperature Dependence of the Electron Diffusion Coefficient in Electrolyte-Filled TiO2
Kopidakis, Nikos
Benkstein, Kurt D.
Frank, Arthur J.
Yuan, Quan
Schiff, Eric A
Article
2006-01-01T08:00:00Z
Nanocrystalline materials
Photoconduction and photovoltaic effects
Disordered solids
Physics
<p>The temperature and photoexcitation density dependences of the electron transport dynamics in electrolytefilled mesoporous TiO2 nanoparticle films were investigated by transient photocurrent measurements. The thermal activation energy of the diffusion coefficient of photogenerated electrons ranged from 0.19–0.27 eV, depending on the specific sample studied. The diffusion coefficient also depends strongly on the photoexcitation density; however, the activation energy has little, if any, dependence on the photoexcitation density. The light intensity dependence can be used to infer temperature-independent dispersion parameters in the range 0.3–0.5. These results are inconsistent with the widely used transport model that assumes multiple trapping of electrons in an exponential conduction-band tail. We can also exclude a model allowing for widening of a band tail with increased temperature. Our results suggest that structural, not energetic, disorder limits electron transport in mesoporous TiO2. The analogy between this material and others in which charge transport is limited by structural disorder is discussed.</p>
<p>First author and SU authors listed, for additional authors see the article.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/38
oai:surface.syr.edu:phy-1046
2012-09-07T13:57:20Z
publication:coscde
publication:dphy
publication:phy
publication:cas
Amorphous Silicon Based Solar Cells
Deng, Xunming
Schiff, Eric A
Book Chapter
2003-01-01T08:00:00Z
amorphous silicon
solar cells
Physics
<p>Crystalline semiconductors are very well known, including silicon (the basis of the integrated circuits used in modern electronics), Ge (the material of the first transistor), GaAs and the other III-V compounds (the basis for many light emitters), and CdS (often used as a light sensor). In crystals, the atoms are arranged in near-perfect, regular arrays or lattices. Of course, the lattice must be consistent with the underlying chemical bonding properties of the atoms. For example, a silicon atom forms four covalent bonds to neighboring atoms arranged symmetrically about it. This “tetrahedral” configuration is perfectly maintained in the “diamond” lattice of crystal silicon.</p>
http://creativecommons.org/licenses/by/3.0/
https://surface.syr.edu/phy/47
1460113/simple-dublin-core/100//