Eigenvalue distribution of the Dirac operator at finite temperature with (2+1)-flavor dynamical quarks using the HISQ action

TL;DR

This study examines the eigenvalue distribution of the Dirac operator in finite-temperature (2+1)-flavor QCD using the HISQ action, revealing behavior of near-zero modes and critical phenomena near the phase transition.

Contribution

First detailed analysis of Dirac eigenvalue density in (2+1)-flavor QCD at finite temperature with HISQ action near the critical point.

Findings

Near-zero modes dominate below T_c and diminish with increasing temperature.

No clear gap in eigenvalue density up to 1.1 T_c.

Eigenvalue density near T_c shows power-law behavior consistent with critical scaling.

Abstract

We report on the behavior of the eigenvalue distribution of the Dirac operator in (2+1)-flavor QCD at finite temperature, using the HISQ action. We calculate the eigenvalue density at several values of the temperature close to the pseudocritical temperature. For this study we use gauge field configurations generated on lattices of size $32^3 \times 8$ with two light quark masses corresponding to pion masses of about 160 and 115 MeV. We find that the eigenvalue density below $T_c$ receives large contributions from near-zero modes which become smaller as the temperature increases or the light quark mass decreases. Moreover we find no clear evidence for a gap in the eigenvalue density up to 1.1$T_c$. We also analyze the eigenvalue density near $T_c$ where it appears to show a power-law behavior consistent with what is expected in the critical region near the second order chiral symmetry restoring phase transition in the massless limit.