Testing Fermion Actions: Scaling in the Schwinger Model

TL;DR

This paper evaluates the scaling properties of various fermion actions in the 2D Schwinger model and explores methods to efficiently simulate overlap fermions using approximations within Hybrid Monte Carlo algorithms.

Contribution

It introduces a new approach for dynamic overlap fermion simulation by using approximate operators and stochastic correction techniques.

Findings

Different fermion actions exhibit distinct scaling behaviors.

Approximate overlap operators can be effectively used in HMC simulations.

Stochastic correction methods improve the accuracy of approximate overlap simulations.

Abstract

We test the scaling behaviour of Wilson, hypercube, maximally twisted mass and overlap fermion actions in dynamical simulations of the 2-dimensional massive Schwinger model. We also present possibilities to simulate overlap fermions dynamically by replacing the exact overlap operator by an approximate version. This approximation is used either as only the guidance Hamiltonian, keeping the exact overlap operator as the accept/reject Hamiltonian or for both, the guidance and accept/reject Hamiltonian in the Hybrid Monte Carlo algorithm. In the latter case we test whether the approximation error can be corrected for by computing the determinant ratio of the exact and the approximate overlap operators stochastically.