Translating topological benefits in very cold lattice simulations

TL;DR

This paper explores using very long temporal lattice extents in lattice QCD simulations with stabilized Wilson fermions to mitigate topological freezing effects, enabling more accurate calculations of certain observables at fine lattice spacings.

Contribution

It introduces a novel approach of using elongated time directions in lattice simulations to reduce topological freezing effects and improve observable calculations.

Findings

First results from $N_f=3$ ensembles with $T=2304$ and $a=0.055$ fm.

Identification of scalar-scalar meson correlator as a useful probe.

Demonstration of potential benefits of long-$T$ lattices in topological studies.

Abstract

Master-field simulations offer an approach to lattice QCD in which calculations are performed on a small number of large-volume gauge-field configurations. The latter is advantageous for simulations in which the global topological charge is frozen due to a very fine lattice spacing, as the effect of this on observables is suppressed by the spacetime volume. Here we make use of the recently developed Stabilised Wilson Fermions to investigate a variation of this approach in which only the temporal direction ($T$) is taken larger than in traditional calculations. As compared to a hyper-cubic lattice geometry, this has the advantage that finite-$L$ effects can be useful, e.g. for multi-hadron observables, while compared to open boundary conditions, time-translation invariance is not lost. In this proof-of-concept contribution, we study the idea of using very cold (i.e. long-$T$) lattices to topologically "defrost" observables at fine lattice spacing. We identify the scalar-scalar meson two-point correlation function as a useful probe and present first results from $N_f=3$ ensembles with time extents up to $T=2304$ and a lattice spacing of $a=0.055\,\rm{fm}$.