Vanishing Thermal Mass in the Strongly Coupled QCD/QED medium

TL;DR

This paper nonperturbatively studies thermal quasifermions in strongly coupled QCD/QED, revealing that their thermal mass diminishes and vanishes at strong coupling, with implications for quark-gluon plasma properties.

Contribution

It provides the first nonperturbative analysis showing the thermal mass of quasifermions vanishes in strong coupling regimes using Dyson-Schwinger equations.

Findings

Thermal mass decreases with increasing coupling and disappears at strong coupling.

Imaginary part of the mass function indicates a persistent decay width proportional to g^2 T log(1/g).

Results imply quasifermions in quark-gluon plasma are effectively massless at strong coupling.

Abstract

In this paper we perform a nonperturbative analysis of a thermal quasifermion in thermal QCD/QED by studying its self-energy function through the Dyson-Schwinger equation with the hard-thermal-loop resummed improved ladder kernel. Our analysis reveals several interesting results, some of which may force us to change the image of the thermal quasifermion: (1) The thermal mass of a quasifermion begins to decrease as the coupling gets stronger and finally disappears in the strong coupling region,(2) the imaginary part of the chiral invariant mass function (i.e., the decay width of the quasifermion) persists to have $O(g^2 T \log (1/g))$ behavior. Present results suggest that in the recently produced strongly coupled quark-gluon-plasma, the thermal mass of a quasifermion should vanish. We also briefly comment on evidence of the existence of a massless, or an ultrasoft mode.