Dynamical overlap fermion simulations with a preconditioned Hybrid Monte Carlo force

TL;DR

This paper introduces a new method for simulating 2-flavour Schwinger model using dynamical Ginsparg-Wilson fermions with an overlap hypercube operator, demonstrating algorithmic viability and accurate physical results.

Contribution

It presents a novel approach to dynamical overlap fermion simulations using a hypercube kernel, improving computational efficiency and confirming theoretical predictions.

Findings

High locality of the formulation

Successful evaluation of the chiral condensate at light masses

Good agreement with analytic predictions at weak coupling

Abstract

We present simulation results for the 2-flavour Schwinger model with dynamical Ginsparg-Wilson fermions. Our Dirac operator is constructed by inserting an approximately chiral hypercube operator into the overlap formula, which yields the overlap hypercube operator. Due to the similarity with the hypercubic kernel, a low polynomial of this kernel can be used as a numerically cheap way to evaluate the fermionic part of the Hybrid Monte Carlo force. We verify algorithmic requirements like area conservation and reversibility, and we discuss the viability of this approach in view of the acceptance rate. Next we confirm a high level of locality for this formulation. Finally we evaluate the chiral condensate at light fermion masses, based on the density of low lying Dirac eigenvalues in different topological sectors. The results represent one of the first measurements with dynamical overlap fermions, and they agree very well with analytic predictions at weak coupling.