Applications of Holography to Strongly Coupled Plasmas

Abstract

This thesis is concerned with the analysis of universal properties of several physical observables in strongly coupled plasmas as they are studied in heavy-ion collisions – for example at the LHC. The focus lies on the energy loss of a uniformly moving and of a rotating quark, the running coupling as defined via the free energy of static quark-antiquark (QQbar)-pairs and the maximum distance (screening distance) of a (QQbar)-pair in the hot plasma. All of them have been computed using the AdS/CFT correspondence. In order to discover a universal behaviour in the observables, computations have been worked out in the free gravity theory in AdS5 space-time which is dual to N=4 supersymmetric Yang–Mills theory as well as in three deformed, non-conformal metric models. Two of these are solutions to Einstein equations derived from a supergravity action. It has been shown that the energy loss of uniformly moving and of rotating quarks is very robust in all deformed models compared to the conformal results. In the case of the running coupling the introduction of deformations leads to a universal increase for larger (QQbar)-distances. This is qualitatively consistent with lattice QCD simulations. For the screening distance a proof has been presented for the conjecture that the conformal N=4T value for the screening distance is a lower bound for small perturbations around the conformal solution. Such a behaviour had been observed before in numerical studies in all of the above-mentioned deformed metric models.