PhD Defenses

PHYSICS DISSERTATION DEFENSE: Evan Coleman

Date
Mon July 11th 2022, 12:00 - 1:00pm
Stanford Student Observatory

Linda Cicero

Ph.D. Candidate:  Evan Coleman

Research Advisor: 
Eva Silverstein

Date: July 11th, 2022
Time: 12pm — 1pm


Zoom Link: 
https://stanford.zoom.us/j/94356958113

Zoom Password: email nickswan [at] stanford.edu (nickswan[at]stanford[dot]edu) for password.

 

Title: 
Finite-Volume Holography and the Cosmological Constant

Abstract: 
Holographic duality has revolutionized research in quantum gravity over the past 25 years. It postulates that the partition functions of gravitational systems with negative cosmological constant (whose classical solutions are Anti-de Sitter or AdS spacetimes) correspond exactly to those of conformal field theories (CFTs) with one fewer spatial dimension. This "AdS/CFT correspondence" provides a tractable and non-perturbative computational framework which circumvents the traditional challenges presented by the direct quantization of gravity, which is non-renormalizable. However, observational evidence indicates that our universe has a positive cosmological constant, i.e. that its late-time description (ignoring metastability) is asymptotically de Sitter, rather than Anti-de Sitter. It is an open challenge to formulate holography consistently with such empirical observations, but restricting the duality to a causal patch of de Sitter spacetime gives us a number of handles on the problem. Recent research heavily indicates that the holographic degrees of freedom associated to bulk gravity in the de Sitter observer patch (the causal patch we in principle inhabit) should live at the cosmic horizon. In this thesis, I will demonstrate how proposals for a finite-volume formulation of Anti-de Sitter holography, stemming from properties of TTbar-deformed 2D quantum field theories, can be modified to account for the Gibbons-Hawking entropy in 3D de Sitter space and thus verify this statement. I also discuss various tests of the finite-volume correspondence, demonstrating how bulk boundary conditions can be changed, and presenting top-down analogs in string theory.