The diagonal and off-diagonal quark number susceptibility of high temperature and finite density QCD

TL;DR

This paper investigates quark number susceptibilities in high-temperature QCD using lattice simulations of EQCD, revealing temperature-dependent deviations from perturbative results and consistency with 4d lattice data.

Contribution

It provides the first lattice-based analysis of both diagonal and off-diagonal quark susceptibilities at finite temperature and density in EQCD, including analytic continuation techniques.

Findings

Diagonal susceptibility aligns with perturbation theory above 20T_c.

Significant deviations from perturbative results below 20T_c.

Off-diagonal susceptibility agrees with perturbation theory at 10T_c.

Abstract

We study the quark number susceptibility of the hot quark-gluon plasma at zero and non-zero quark number density, using lattice Monte Carlo simulations of an effective theory of QCD, electrostatic QCD (EQCD). Analytic continuation is used to obtain results at non-zero quark chemical potential. We measure both flavor singlet (diagonal) and non-singlet (off-diagonal) quark number susceptibilities. The diagonal susceptibility approaches the perturbative result above 20T_c, but below that temperature we observe significant deviations. The results agree well with 4d lattice data down to temperatures 2T_c. The off-diagonal susceptibility is more prone to statistical and systematic errors, but the results are consistent with perturbation theory already at 10T_c.