Topological tunneling with Dynamical overlap fermions

TL;DR

This paper introduces a method to improve topological tunneling in lattice QCD simulations with dynamical overlap fermions, significantly reducing auto-correlation times at low fermion masses.

Contribution

The authors propose a novel approach that projects out small Wilson eigenvectors and treats the correction determinant exactly, enhancing tunneling efficiency without much extra computational cost.

Findings

Increased tunneling rates between topological sectors.

Reduced auto-correlation times at low fermion masses.

Effective method with minimal additional computational expense.

Abstract

Tunneling between different topological sectors with dynamical chiral fermions is difficult because of a poor mass scaling of the pseudo-fermion estimate of the determinant. For small fermion masses it is virtually impossible using standard methods. However, by projecting out the small Wilson eigenvectors from the overlap operator, and treating the correction determinant exactly, we can significantly increase the rate of topological sector tunneling and reduce substantially the auto-correlation time. We present and compare a number of different approaches, and advocate a method which allows topological tunneling even at low mass with little addition to the computational cost.