Quark-gluon plasma physics

Nuclear matter under extreme conditions, such as those generated in heavy-ion collisions and presumably existing in the interior of compact stars, dissolves into the otherwise confined degrees of freedom of quarks and gluons which are described by the fundamental theory of quantum chromodynamics. Recent results from the ultrarelativistic heavy-ion collider RHIC at Brookhaven indicate unexpectedly strong collective phenomena in this new state of matter such as an apparent ratio of viscosity over entropy density much lower than ever observed in any physical system and extremely early thermalization. In the comparatively low-temperature but ultra-dense state of matter in the interior of neutron stars the existence of quark matter could reveal itself through anomalous cooling properties. The aim of this project is to investigate equilibrium and nonequilibrium properties of the quark-gluon plasma that are relevant to these phenomena, namely so-called non-Fermi-liquid effects on specific heat and neutrino emissitivity in ultradegenerate quark matter, and chromomagnetic instabilities in ultra\-relativistically hot anisotropic quark-gluon plasma.

Project P19526 "Quark-gluon-plasma physics" has produced new results on the dynamics of subnuclear particles in the novel state of matter called "quark-gluon plasma" that can nowadays be produced in high-energy collisions of gold and lead ions and which is believed to have filled the entire universe during the first few microseconds after the Big Bang. Since November 2010 the Large Hadron Collider at CERN has begun to investigate the quark-gluon plasma at much higher energies than previously possible, and the results of this project indicate that the dynamics in the first few yoctoseconds is governed by plasma instabilities known from conventional electrodynamic plasmas, but complicated by the specific selfinteractions of gluons. Using the new supercomputer VSC, these plasma instabilities have been simulated in extremely time- and memory-intensive numerical calculations, and will be used in future comparisons with heavy-ion data. A comparatively cold but equally dense form of the quark-gluon plasma could exist in the interior of certain extremely dense compact stars, where it may be in a superconducting state with the charge of quarks and gluons playing the role of electric charge. A further main focus of the project has been the exploration of the possible phases of dense quark matter and quantitative calculations of its properties.