Quark spectral density and a strongly-coupled QGP

TL;DR

This paper uses the maximum entropy method to analyze the quark spectral density in a strongly-coupled quark-gluon plasma, revealing a persistent zero mode above the chiral symmetry restoration temperature.

Contribution

It introduces a nonperturbative zero mode in the quark spectral density at high temperatures, indicating a strongly-coupled quark-gluon plasma state.

Findings

Identification of a zero mode in the spectral function above T_c

Persistence of the zero mode up to 1.8 T_c

System behaves as a strongly-coupled state near T_c

Abstract

The maximum entropy method is used to compute the dressed-quark spectral density from the self-consistent numerical solution of a rainbow truncation of QCD's gap equation at temperatures above that for which chiral symmetry is restored. In addition to the normal and plasmino modes, the spectral function also exhibits an essentially nonperturbative zero mode for temperatures extending to 1.4-1.8-times the critical temperature, T_c. In the neighbourhood of T_c, this long-wavelength mode contains the bulk of the spectral strength and so long as this mode persists, the system may fairly be described as a strongly-coupled state of matter.