Full QCD Algorithms towards the Chiral Limit

TL;DR

This paper reviews the performance of algorithms, especially the Hybrid-Monte-Carlo, for simulating full QCD as the sea-quark mass approaches the chiral limit, highlighting recent improvements and alternatives.

Contribution

It introduces a modified pseudo-fermion action for HMC and summarizes recent results from collaborations using this approach.

Findings

Improved HMC performance with modified pseudo-fermion action

Successful application of the approach in large-scale simulations

Discussion of alternative algorithms like Multiboson

Abstract

I discuss the behaviour of algorithms for dynamical fermions as the sea-quark mass decreases. I focus on the Hybrid-Monte-Carlo (HMC) algorithm applied to two degenerate flavours of Wilson fermions. First, I briefly review the performance obtained in large scale HMC simulations. Then I discuss a modified pseudo-fermion action for the HMC simulation that has been introduced three years ago. I summarize recent results obtained with this pseudo-fermion action by the QCDSF and the ALPHA collaborations. I comment on alternatives to the HMC, like the Multiboson algorithm and variants of it.