Quark mass, scale and volume dependence of topological charge density correlator in Lattice QCD

TL;DR

This study investigates how the topological charge density correlator in lattice QCD depends on quark mass, lattice spacing, and volume, revealing detailed behaviors of the correlator and implications for topological susceptibility.

Contribution

It provides a comprehensive analysis of the topological charge density correlator's dependence on lattice parameters and quark mass, elucidating mechanisms behind susceptibility suppression.

Findings

The TCDC is negative beyond a positive core, which shrinks with decreasing lattice spacing.

Decreasing volume reduces the contact term and positive core radius, increasing negative peak and suppressing susceptibility.

Lower quark mass decreases the contact term and positive core radius, while increasing the negative peak, leading to susceptibility suppression.

Abstract

We study the two-point Topological Charge Density Correlator (TCDC) in lattice QCD with two degenerate flavours of naive Wilson fermions and unimproved Wilson gauge action at two values of lattice spacings and different volumes, for a range of quark masses. Configurations are generated with DDHMC algorithm and smoothed with HYP smearing. In order to shed light on the mechanisms leading to the observed suppression of topological susceptibility with respect to the decreasing quark mass and decreasing volume, in this work, we carry out a detailed study of the two-point TCDC. We have shown that, (1) the TCDC is negative beyond a positive core and radius of the core shrinks as lattice spacing decreases, (2) as the volume decreases, the magnitude of the contact term and the radius of the positive core decrease and the magnitude of the negative peak increases resulting in the suppression of the topological susceptibility as the volume decreases, (3) the contact term and radius of the positive core decrease with decreasing quark mass at a given lattice spacing and the negative peak increases with decreasing quark mass resulting in the suppression of the topological susceptibility with decreasing quark mass, (4) increasing levels of smearing suppresses the contact term and the negative peak keeping the susceptibility intact and (5) both the contact term and the negative peak diverge in nonintegrable fashion as lattice spacing decreases.