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Zibakhshshabgahi, Rana

University of British Columbia

In this thesis, we develop a holographic method through the anti de Sitter/conformal field theory (AdS/CFT) correspondence for analyzing the thermodynamic features of a class of strongly coupled quantum field theories and discuss the applications of our work for building cosmological models. We aim to explore cosmologies whose evolution is sourced by the equation of state of such class of holographic quantum field theories which are given by relevant deformations of a conformal field theory. AdS/CFT is a powerful duality which relates quantum gravity in asymptotically anti-de Sitter (AdS) spacetimes to conformal field theories (CFT) living on its boundary. Through this duality we can use classical gravity in five dimensions to tackle otherwise intractable problems on a class of strongly interacting quantum field theories in four dimensions. In our bottom up holographic approach which consists of Einstein gravity coupled to a scalar field, we find the equation of state associated to a deformation away from a conformal field theory fixed point in the UV. By analyzing the equation of state, we find that the low temperature limit is governed by a Casimir contribution with w = p/e = -1 while the high temperature behaviour is given by a conformal equation of state i.e., w=1/3. In our simplest model, we find a puzzle in the low temperature limit; the quantum field theory seems to possess negative specific heat. We believe this suggests a new branch of solutions which are beyond our semi-classical model of the bulk dual physics. We then proceed to construct a cosmological model which is sourced by holographic quantum matter. A major challenge in studying such cosmological models is that calculations via holography with dynamical background require fairly complicated numerical techniques. We simplify our construction by restricting our attention to cosmologies which expand slowly enough so that the quantum field theory remains in thermal equilibrium at all times. We characterize the parameter space in which our model would fall in this so called "quasi-static" regime. We also discuss the steps for finding the scale factor evolution sourced by the strongly coupled non-conformal matter within this scenario.

Text

2023-10-19

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/86234

Physics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/