Topological susceptibility in 2+1 flavors lattice QCD with domain-wall fermions

TL;DR

This paper measures the topological susceptibility in 2+1 flavor lattice QCD with domain-wall fermions, confirming theoretical predictions and extracting the chiral condensate.

Contribution

It provides the first lattice QCD calculation of topological susceptibility with 2+1 flavors using domain-wall fermions and derives the chiral condensate from it.

Findings

Topological susceptibility agrees with chiral effective theory in small quark mass regime.

Chiral condensate estimated as (259(6)(9) MeV)^3.

Method demonstrates reliable computation of topological charge in lattice QCD.

Abstract

We measure the topological charge and its fluctuation for the gauge configurations generated by the RBC and UKQCD Collaborations using 2+1 flavors of domain-wall fermions on the 16^3 x 32 lattice (L \simeq 2 fm) with length 16 in the fifth dimension at inverse lattice spacing a^{-1} \simeq 1.62 GeV. From the spectral flow of the Hermitian operator H_w (2 + \gamma_5 H_w)^{-1}, we obtain the topological charge Q_t of each gauge configuration in the three ensembles with light sea quark masses m_q a = 0.01, 0.02, and 0.03, and with the strange quark mass fixed at m_s a = 0.04. From our result of Q_t, we compute the topological susceptibilty \chi_t = < Q_t^2 > /volume. In the small m_q regime, our result of \chi_t agrees with the chiral effective theory. Using the formula \chi_t = \Sigma / (m_u^{-1} + m_d^{-1} + m_s^{-1}) by Leutwyler-Smilga, we obtain the chiral condensate \Sigma^MSbar(2 GeV) = [259(6)(9) MeV]^3.