The University of Southampton
University of Southampton Institutional Repository

Entanglement and excitations in gauge/gravity duality

Entanglement and excitations in gauge/gravity duality
Entanglement and excitations in gauge/gravity duality
Gauge/gravity duality, also known as holography, relates quantum field theories to theories of gravity. When one theory is strongly coupled, and therefore difficult to study directly, the other is weakly coupled. In this thesis, we study a variety of phenomena in strongly coupled quantum field theories by performing calculations in their gravitational duals.
We compute entanglement entropy in a variety of holographic systems, paying particular attention to its long-distance behaviour, characterised by a term proportional to surface area. This term is known to decrease along Lorentz-invariant renormalisation group flows, suggesting that it may count massless degrees of freedom. We find that more general deformations may increase this area term, possibly indicating an enhanced number of long-distance degrees of freedom. We observe a correlation between this enhancement and the emergence of new scaling symmetry at long distances.
Next, we study the spectrum of collective excitations in a holographic model of a non-Fermi liquid. At high temperatures, the spectrum of collective excitations includes hydrodynamic sound waves. As in similar models, we observe that sound-like modes also exist at low temperatures. Such modes are known as holographic zero sound. We study the changing properties of holographic zero sound and the emergence of hydrodynamic behaviour at high temperatures as we vary the parameters of the model. We find that for certain values of the parameters, the temperature-dependence of holographic zero sound qualitatively resembles that of a normal Fermi liquid.
Finally, we study the entanglement entropy contribution of surface defects in a six dimensional quantum field theory of relevance to M-theory, which is a candidate theory of quantum gravity. We find that the entanglement entropy does not monotonically decrease along renormalisation group flows on these defects, ruling it out as a potential measure of degrees of freedom. On the other hand, we find that two of the contributions of the defect to the Weyl anomaly of the quantum field theory decrease along all of the flows that we study.
University of Southampton
Rodgers, Ronald, James
50624100-db56-478e-9b46-0db869df1020
Rodgers, Ronald, James
50624100-db56-478e-9b46-0db869df1020
O'bannon, Andrew
f0c14b6c-5b74-4319-8432-f9eba1e20cf3

Rodgers, Ronald, James (2019) Entanglement and excitations in gauge/gravity duality. University of Southampton, Doctoral Thesis, 201pp.

Record type: Thesis (Doctoral)

Abstract

Gauge/gravity duality, also known as holography, relates quantum field theories to theories of gravity. When one theory is strongly coupled, and therefore difficult to study directly, the other is weakly coupled. In this thesis, we study a variety of phenomena in strongly coupled quantum field theories by performing calculations in their gravitational duals.
We compute entanglement entropy in a variety of holographic systems, paying particular attention to its long-distance behaviour, characterised by a term proportional to surface area. This term is known to decrease along Lorentz-invariant renormalisation group flows, suggesting that it may count massless degrees of freedom. We find that more general deformations may increase this area term, possibly indicating an enhanced number of long-distance degrees of freedom. We observe a correlation between this enhancement and the emergence of new scaling symmetry at long distances.
Next, we study the spectrum of collective excitations in a holographic model of a non-Fermi liquid. At high temperatures, the spectrum of collective excitations includes hydrodynamic sound waves. As in similar models, we observe that sound-like modes also exist at low temperatures. Such modes are known as holographic zero sound. We study the changing properties of holographic zero sound and the emergence of hydrodynamic behaviour at high temperatures as we vary the parameters of the model. We find that for certain values of the parameters, the temperature-dependence of holographic zero sound qualitatively resembles that of a normal Fermi liquid.
Finally, we study the entanglement entropy contribution of surface defects in a six dimensional quantum field theory of relevance to M-theory, which is a candidate theory of quantum gravity. We find that the entanglement entropy does not monotonically decrease along renormalisation group flows on these defects, ruling it out as a potential measure of degrees of freedom. On the other hand, we find that two of the contributions of the defect to the Weyl anomaly of the quantum field theory decrease along all of the flows that we study.

Text
thesis_Final - Version of Record
Available under License University of Southampton Thesis Licence.
Download (3MB)

More information

Published date: September 2019

Identifiers

Local EPrints ID: 437363
URI: http://eprints.soton.ac.uk/id/eprint/437363
PURE UUID: 76c17e7f-6ca0-4da8-9075-e62c3f46cc02
ORCID for Ronald, James Rodgers: ORCID iD orcid.org/0000-0002-4826-6540
ORCID for Andrew O'bannon: ORCID iD orcid.org/0000-0001-7862-783X

Catalogue record

Date deposited: 24 Jan 2020 17:33
Last modified: 27 Jan 2020 13:49

Export record

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×