Dynamical FLIC Fermions

TL;DR

This paper introduces a new projection technique for FLIC fermions in lattice QCD that enables the use of standard Hybrid Monte Carlo algorithms for dynamical simulations, overcoming previous differentiability issues.

Contribution

It proposes an alternative reunitarisation method for fat link actions that allows efficient dynamical fermion simulations with standard HMC algorithms.

Findings

New projection technique enables differentiable fat link reunitarisation.

Allows the use of standard HMC algorithms for dynamical FLIC fermions.

Facilitates more efficient lattice QCD simulations with fat link actions.

Abstract

The use of APE smearing or other blocking techniques in fermion actions can provide many advantages. There are many variants of these fat link actions in lattice QCD currently, such as FLIC fermions. The FLIC fermion formalism makes use of the APE blocking technique in combination with a projection of the blocked links back into the special unitary group. This reunitarisation is often performed using an iterative maximisation of a gauge invariant measure. This technique is not differentiable with respect to the gauge field and thus prevents the use of standard Hybrid Monte Carlo simulation algorithms. The use of an alternative projection technique circumvents this difficulty and allows the simulation of dynamical fat link fermions with standard HMC and its variants.