Determination of the chiral condensate from QCD Dirac spectrum on the lattice

TL;DR

This paper computes the QCD chiral condensate using lattice simulations with dynamical overlap fermions, matching eigenvalue spectra to chiral perturbation theory to determine the condensate in the massless quark limit.

Contribution

It introduces a precise lattice QCD method employing overlap fermions and spectral analysis to determine the chiral condensate, incorporating next-to-leading order chiral perturbation theory.

Findings

Chiral condensate values for 2, 2+1, and 3 flavor QCD.

Successful matching of lattice data with chiral perturbation theory.

Determination of the condensate in the chiral limit.

Abstract

We calculate the chiral condensate of QCD with 2, 2+1 and 3 flavors of sea quarks. Lattice QCD simulations are performed employing dynamical overlap fermions with up and down quark masses covering a range between 3 and 100 MeV. On L ~ 1.8-1.9 fm lattices at a lattice spacing ~ 0.11 fm, we calculate the eigenvalue spectrum of the overlap-Dirac operator. By matching the lattice data with the analytical prediction from chiral perturbation theory at the next-to-leading order, the chiral condensate in the massless limit of up and down quarks is determined.