Rust, Felix (2009): Inmedium effects in the holographic quarkgluon plasma. Dissertation, LMU München: Faculty of Physics 

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Abstract
In this dissertation we use the gauge/gravity duality to investigate various properties of strongly coupled gauge theories, which we interpret as models for the quarkgluon plasma (QGP). In particular, we use variants of the D3/D7 setup as an implementation of the topdown approach of connecting string theory with phenomenologically relevant gauge theories. We focus on the effects of finite temperature and finite density on fundamental matter in the holographic quarkgluon plasma, which we model as the N=2 hypermultiplet in addition to the N=4 gauge multiplet of supersymmetric YangMills theory. As a key ingredient we develop a setup in which we can describe vector meson spectra in the holographic plasma at finite temperature and either baryon or isospin density. The resulting spectral functions are valid for all values of quark mass and temperature. They show the expected features of meson melting at high temperatures and are in agreement with the previously derived spectra for the zero temperature and zero density limit. Moreover, we are able to give a description of inmedium effects of finite particle density which are in qualitative agreement with phenomenological models and experimental observations. The description of vector meson excitations furthermore allows for a demonstration of the splitting of their spectrum at finite isospin chemical potential. In the effort to better understand transport processes in the QGP, we then study various diffusion coefficients in the quarkgluon plasma, including their dependence on temperature and particle density. In particular, we perform a simple calculation to obtain the diffusion coefficient of baryon charge and we derive expressions to obtain the isospin diffusion coefficient. Furthermore, we make use of an effective model to study the diffusion behavior of mesons in the plasma by setting up a kinetic model. The setup we chose allows to carry out computations at weak and strong coupling which we compare in order to estimate the effects of the coupling strength on mesonic diffusion and therewith equilibration processes in the QGP. Finally, we observe the implications of finite temperature and finite baryon or isospin density on the phase structure of fundamental matter in the holographic plasma. As one consequence we find a phase transition in the baryon diffusion coefficient which vanishes at a critical value of the particle density. The critical density we quantify matches the values of the according critical densities previously found in the phase transitions of other quantities. More important, we observe a new phase transition occurring when the isospin chemical potential excesses a critical bound, which depends on the temperature of the medium. Beyond this point we observe an instability of the system under consideration. In this way we trace out the border of a new phase in the phase diagram of fundamental matter in the holographic plasma.
Item Type:  Thesis (Dissertation, LMU Munich) 

Keywords:  AdS/CFT, Dbranes, holography, quarkgluon plasma 
Subjects:  600 Natural sciences and mathematics 600 Natural sciences and mathematics > 530 Physics 
Faculties:  Faculty of Physics 
Language:  English 
Date Accepted:  4. August 2009 
1. Referee:  Erdmenger, Johanna 
Persistent Identifier (URN):  urn:nbn:de:bvb:19104729 
MD5 Checksum of the PDFfile:  f62ca36e8b754cde0e69a9bcf319c7b9 
Signature of the printed copy:  0001/UMC 17979 
ID Code:  10472 
Deposited On:  25. Aug 2009 12:17 
Last Modified:  16. Oct 2012 08:30 