Ngo Thanh, Hai (2011): Gauge/gravity duality: From quantum phase transitions towards outofequilibrium physics. Dissertation, LMU München: Faculty of Physics 

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Abstract
In this dissertation we use gauge/gravity duality to investigate various phenomena of strongly coupled field theories. Of special interest are quantum phase transitions, quantum critical points, transport phenomena of charges and the thermalization process of strongly coupled medium. The systems studied in this thesis might be used as models for describing condensed matter physics in a superfluid phase near the quantum critical point and the physics of quarkgluon plasma (QGP), a deconfinement phase of QCD, which has been recently created at the Relativistic Heavy Ion Collider (RHIC). Moreover, we follow the line of considering different gravity setups whose dual field descriptions show interesting phenomena of systems in thermal equilibrium, slightly outofequilibrium and farfromequilibrium. We first focus on systems in equilibrium and construct holographic superfluids at finite baryon and isospin charge densities. For that we use two different approaches, the bottomup with an U(2) EinsteinYangMills theory with backreaction and the topdown approach with a D3=D7 brane setup with two coincident D7brane probes. In both cases we observe phase transitions from a normal to a superfluid phase at finite and also at zero temperature. In our setup, the gravity duals of superfluids are Antide Sitter black holes which develop vectorhair. Studying the order of phase transitions at zero temperature, in the D3=D7 brane setup we always find a second order phase transition, while in the EinsteinYangMills theory, depending on the strength of the backreaction, we obtain a continuous or first order transition. We then move to systems which are slightly outofequilibrium. Using the D3/D7 brane setup with Nc coincident D3branes and Nf coincident D7brane probes, we compute transport coefficients associated with massive N = 2 supersymmetric hypermultiplet fields propagating through an N = 4 SU(Nc) super YangMills plasma inthe limit of Nf << Nc. Introducing a baryon number density and arbitrary constant electric and magnetic fields, we compute all components of the conductivity tensor associated with transport of baryon number charge. Determining the contribution that the flavor degrees of freedom make to the stressenergy tensor, we are able to identify the rates of energy and momentum loss of the flavor field to the plasma. Going towards systems farfromequilibrium, we investigate a timedependent geometry consisting of a mirror moving in the bulk of the Antide Sitter space. This geometry can be seen as a toy model which is relevant to the formulation of holographic thermalization in strongly coupled field theory. For this configuration, we establish a procedure for calculating timedependent twopoint functions of scalar fluctuations, based on a WKB approximation. We test our method on two sample trajectories for the mirror, and find that the singularity structure of the twopoint functions is in agreement with the geometric optics.
Item Type:  Thesis (Dissertation, LMU Munich) 

Keywords:  AdS/CFT correspondence, holographic superfluid, quantum phase transitions, quantum critical point, flavor transport, holographic thermalization 
Subjects:  600 Natural sciences and mathematics 600 Natural sciences and mathematics > 530 Physics 
Faculties:  Faculty of Physics 
Language:  English 
Date Accepted:  14. July 2011 
1. Referee:  Erdmenger, Johanna 
Persistent Identifier (URN):  urn:nbn:de:bvb:19133143 
MD5 Checksum of the PDFfile:  52af8052b6ee0798abff6de95a897c6b 
Signature of the printed copy:  0001/UMC 19659 
ID Code:  13314 
Deposited On:  23. Aug 2011 08:28 
Last Modified:  16. Oct 2012 08:52 