Recent thermodynamic results from lattice QCD analyzed within a quasi-particle model

TL;DR

This paper analyzes recent lattice QCD results at high temperature using a quasi-particle model, highlighting differences in thermodynamic behavior and their implications for transport properties.

Contribution

It introduces a quasi-particle model to interpret recent lattice QCD results, examining discrepancies and their effects on thermodynamic and transport properties of QCD matter.

Findings

Recent lattice results show a slower increase in energy density.

Discrepancies affect predictions of shear and bulk viscosities.

The quasi-particle model accounts for differences in trace anomaly.

Abstract

The thermodynamic behavior of QCD matter at high temperature is currently studied by lattice QCD theory. The main features are the fast rise of the energy density $\epsilon$ around the critical temperature $T_c$ and the large trace anomaly of the energy momentum tensor $< \Theta_\mu^\mu >=\epsilon - 3 P$ which hints at a strongly interacting system. Such features can be accounted for by employing a massive quasi-particle model with a temperature-dependent bag constant. Recent lattice QCD calculations with physical quark masses by the Wuppertal-Budapest group have shown a slower increase of $\epsilon$ and a smaller $<\Theta_\mu^\mu>$ peak with respect to previous results from the hotQCD collaboration. We investigate the implications of such differences from the point of view of a quasi-particle model, also discussing light and strange quark number susceptibilities. Furthermore, we predict the impact of these discrepancies on the temperature-dependence of the transport properties of matter, like the shear and bulk viscosities.