Date of Award
8-22-2025
Date Published
September 2025
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Physics
Advisor(s)
Jay Hubisz
Keywords
Brane cosmology;Cosmological correlator;Cosmological quasi-particle;Extra dimension;Non-Gaussianities;Scaling law
Subject Categories
Physical Sciences and Mathematics | Physics
Abstract
It is well-established that the two-point correlator of a scalar field in AdS follows either of two scaling laws, ∆± =d/2 ± ν, where ν =Sqrt((d/2)^2+ m^2) is a function of the scalar bulk mass. The transition between these two scalings occurs in the renormalization group evolution from the UV to the IR of a dual 4D conformal theory deformed by a relevant double-trace deformation. In this thesis, we identify a new holographic scaling law, ∆UV = ν, in the context of the AdS/CFT correspondence where there exists a UV cutoff brane. Specifically, when ν > 1, the ∆− scaling that violates the unitarity bound, ∆ ≥d/2 −1, will be replaced by the ∆UV scaling which satisfies the unitarity bound. At the transition between ∆UV and ∆+ scaling, there is a particle-like feature in the spectral density of the two-point correlator. We show that in the 4D dual description, this new scaling behavior corresponds to the two-point function of a fundamental scalar field mixing with a CFT operator O with dimension ∆ ≥ 3 through an irrelevant coupling, λϕO. The interplay between cosmological inflation and strongly coupled dynamics yields transient spectral features, which may leave behind phenomenological signatures in the spectrum of primordial fluctuations, and cosmological observables at late times. We study the spectral features of cosmological correlators in a holographic setting during inflation. AdS/CFT arguments suggest that, for large N , in an inflationary background with Hubble rate H, the spectral density for a scalar operator is a gapped continuum. We demonstrate that there can be additional particle-like peak features in phenomenologically interesting regions in parameter space. We estimate their contribution to cosmological observables and find phenomena that are potentially observable in future experiments. We find the new scaling behavior ∆UV = ν with the existence of these quasi-particles. We comment on how stabilization of conformal symmetry breaking vacua can be correlated with these spectral features and their phenomenology. Sections 1, 3, and 4 review existing literature. Sections 2 and 5 feature original work
Access
Open Access
Recommended Citation
Li, He, "Holographic Scaling and Cosmological Correlators" (2025). Dissertations - ALL. 2210.
https://surface.syr.edu/etd/2210
