Logarithmic link smearing for full QCD

TL;DR

This paper introduces a Lie-algebra based logarithmic smearing technique for gauge links in lattice QCD, enabling differentiable fat links suitable for HMC algorithms and analyzing its impact on plaquette distributions and residual masses.

Contribution

It presents a novel logarithmic link smearing method that is differentiable and applicable to full QCD simulations, improving fermion action filtering.

Findings

Smearing affects plaquette distributions positively.

Residual mass of clover fermions is influenced by the smearing.

Method is compatible with HMC algorithms.

Abstract

A Lie-algebra based recipe for smoothing gauge links in lattice field theory is presented, building on the matrix logarithm. With or without hypercubic nesting, this LOG/HYL smearing yields fat links which are differentiable w.r.t. the original ones. This is essential for defining UV-filtered ("fat link") fermion actions which may be simulated with a HMC-type algorithm. The effect of this smearing on the distribution of plaquettes and on the residual mass of tree-level O(a)-improved clover fermions in quenched QCD is studied.