A variant approach to the overlap action

TL;DR

This paper introduces a computationally efficient variant of the overlap action for lattice QCD, utilizing an approximate overlap action and eigenmodes to significantly reduce calculation costs while maintaining physical accuracy.

Contribution

It presents a novel implementation of the overlap action that is 15-20 times less expensive by using an approximate overlap action and eigenmodes, improving computational efficiency.

Findings

Achieved a 15-20 fold reduction in computational cost.

Successfully computed the quark condensate in finite volume.

Demonstrated the effectiveness of the approximate overlap approach.

Abstract

I describe an implementation of the overlap action, which is built from an action which is itself an approximate overlap action. It appears to be about a factor of 15-20 less expensive to use, than the usual overlap action with the Wilson fermion action as its kernel. Ingredients include a fat link to suppress coupling to dislocations and a free field action with a spectrum which resembles an overlap; much of the gain comes from the use of eigenmodes of the approximate action to begin the overlap calculation. As a physics example, I compute the quark condensate in finite volume in the quenched approximation.