A Numerical Study of Partially Twisted Boundary Conditions

TL;DR

This paper explores the application of partially twisted boundary conditions in lattice QCD simulations, enabling access to a wider range of hadronic momenta with minimal finite-volume errors and noise, improving momentum resolution.

Contribution

It demonstrates that partially twisted boundary conditions effectively improve momentum resolution in lattice simulations without significant additional errors or noise.

Findings

Confirmed the momentum shift effect of twisted boundary conditions.

Showed that these conditions do not add appreciable noise.

Validated the exponential suppression of finite-volume errors.

Abstract

We investigate the use of partially twisted boundary conditions in a lattice simulation with two degenerate flavours of improved Wilson sea quarks. The use of twisted boundary conditions on a cubic volume (L^3) gives access to components of hadronic momenta other than integer multiples of 2*pi/L. Partial twisting avoids the need for new gluon configurations for every choice of momentum, while, as recently demonstrated, keeping the finite-volume errors exponentially small for the physical quantities investigated in this letter. In this study we focus on the spectrum of pseudo scalar and vector mesons, on their leptonic decay constants and on Z_P, the matrix element of the pseudo scalar density between the pseudo scalar meson and the vacuum. The results confirm the momentum shift imposed by these boundary conditions and in addition demonstrate that they do not introduce any appreciable noise. We therefore advocate the use of partially twisted boundary conditions in applications where good momentum resolution is necessary.