Quasiparticle description of the hot and dense quark-gluon plasma

TL;DR

This paper analyzes the collective modes of the quark-gluon plasma at high temperatures and densities, exploring isotropic and anisotropic systems using the HTL approximation, and investigates implications for quark-star models and plasma stability.

Contribution

It provides a quasiparticle framework for understanding the thermodynamics and collective excitations of the quark-gluon plasma, including anisotropic effects and their impact on stability and energy loss.

Findings

Unstable modes exist in anisotropic momentum distributions.

Thermodynamic pressure and entropy are derived and compared with lattice results.

Anisotropy influences collisional energy loss in the plasma.

Abstract

The collective modes of QCD at temperatures and densities above its phase-transition are analyzed for isotropic systems as well as for systems having an anisotropy in momentum-space using the HTL approximation. For isotropic systems, results for the thermodynamic pressure and entropy at finite densities based on a phenomenological description of lattice calculations at vanishing densities are derived and compared to those following from different methods. From the resulting equation of state the mass-radius relationship of so-called quark-stars and other applications are investigated. It is shown that systems with anisotropic momentum-space distributions contain unstable modes in addition to the stable quasiparticle modes, which may be of great importance for the dynamical evolution of an incompletely thermalized quark-gluon plasma. Finally, the effects of the anisotropy on the collisional energy loss are studied.