Improved stochastic estimation of quark propagation with Laplacian Heaviside smearing in lattice QCD

TL;DR

This paper introduces a novel stochastic estimation method using LapH smearing for accurate and efficient calculation of quark propagators in large-volume lattice QCD, improving variance reduction techniques.

Contribution

The paper presents a new stochastic estimation approach with LapH smearing and noise dilution, enhancing accuracy and efficiency in lattice QCD calculations of hadron correlators.

Findings

Effective variance reduction achieved with noise dilution.

Successful application to isoscalar mesons and two-pion systems.

Method suitable for large-volume lattice QCD computations.

Abstract

A new method of stochastically estimating the low-lying effects of quark propagation is proposed which allows accurate determinations of temporal correlations of single-hadron and multi-hadron operators in lattice QCD. The method is well suited for calculations in large volumes. Contributions involving quark propagation connecting hadron sink operators at the same final time can be handled in a straightforward manner, even for a large number of final time slices. The method exploits Laplacian Heaviside (LapH) smearing. ZN noise is introduced in a novel way, and variance reduction is achieved using judiciously-chosen noise dilution projectors. The method is tested using isoscalar mesons in the scalar, pseudoscalar, and vector channels, and using the two-pion system of total isospin I=0,1,2 on large anisotropic 24^3 x 128 lattices with spatial spacing a_s~0.12 fm and temporal spacing a_t~0.034 fm for pion masses mpi~390 and 240 MeV.