Effective noise reduction techniques for disconnected loops in Lattice QCD

TL;DR

This paper reviews advanced noise reduction techniques for stochastic estimation of all-to-all propagators in Lattice QCD, focusing on disconnected contributions to nucleon structure functions, achieving significant computational efficiency improvements.

Contribution

It introduces a combination of known and novel unbiased noise reduction methods tailored for Lattice QCD calculations of disconnected diagrams.

Findings

Reduced computational resources by an order of magnitude

Accurate estimation of strangeness contributions to nucleon properties

Demonstrated effectiveness on nucleon structure function calculations

Abstract

Many Lattice QCD observables of phenomenological interest include so-called all-to-all propagators. The computation of these requires prohibitively large computational resources, unless they are estimated stochastically. This is usually done. However, the computational demand can often be further reduced by one order of magnitude by implementing sophisticated unbiased noise reduction techniques. We combine both well known and novel methods that can be applied to a wide range of problems. We concentrate on calculating disconnected contributions to nucleon structure functions, as one realistic benchmark example. In particular we determine the strangeness contributions to the nucleon, <N|ss|N>, and to the spin of the nucleon, Delta s.