Instantons from over-improved cooling

TL;DR

This paper introduces a method using over-improved cooling and modified lattice actions to identify large instantons in lattice gauge theories, providing numerical evidence for their properties and connection to sphaleron tunneling.

Contribution

It proposes a novel approach combining over-improved cooling and twisted boundary conditions to study large instantons in lattice gauge theories, with numerical validation.

Findings

Largest instantons found in toroidal geometry

Existence of multi-parameter instantons proven with twisted boundaries

Numerical results support the method's effectiveness

Abstract

Lattice artefacts are used, through modified lattice actions, as a tool to find the largest instantons in a toroidal geometry [0,L]^3X[0,T] for T to infinity. It is conjectured that the largest instanton is associated with tunnelling through a sphaleron. Existence of instantons with at least 8 parameters can be proven with the help of twisted boundary conditions in the time direction. Numerical results for SU(2) gauge theory obtained by cooling are presented to demonstrate the viability of the method.