The lattice QCD simulation of the quark-gluon mixed condensate g<\bar{q} \sigma G q> at finite temperature and the phase transition of QCD

TL;DR

This study uses lattice QCD simulations to analyze how the quark-gluon mixed condensate and quark condensate behave with temperature, revealing a sharp change at the QCD phase transition around 280MeV and showing their similar chiral behavior.

Contribution

First lattice QCD measurement of the temperature dependence of the quark-gluon mixed condensate near the QCD phase transition.

Findings

Both condensates sharply decrease around T_c  280MeV.

The ratio m_0^2 remains nearly constant across the phase transition.

Weak thermal effects observed below T_c.

Abstract

The thermal effects on the quark-gluon mixed condensate g<\bar{q} \sigma G q>, which is another chiral order parameter, are studied using the SU(3)c lattice QCD with the Kogut-Susskind fermion at the quenched level. We perform the accurate measurement of the mixed condensate as well as the quark condensate for 0MeV<=T<=500MeV. We observe the sharp decrease of both the condensates around T_c \simeq 280MeV, while the thermal effects below T_c are found to be weak. We also find that the ratio m_0^2 = g<\bar{q} \sigma G q>/<\bar{q}q> is almost independent of the temperature even in the very vicinity of T_c, which indicates that the two condensates have nontrivial similarity in the chiral behaviors. We also present the correlation between the condensates and the Polyakov loop to understand the vacuum structure of QCD.