Lattice QCD with open boundary conditions and twisted-mass reweighting

TL;DR

This paper demonstrates that combining open boundary conditions with twisted-mass reweighting effectively addresses simulation challenges in lattice QCD at small lattice spacings and near-physical quark masses, enabling more stable and accurate computations.

Contribution

It shows that twisted-mass reweighting works with open boundary conditions in lattice QCD, improving simulation stability and enabling physical quantity calculations.

Findings

Twisted-mass reweighting is effective with open boundary conditions.

Algorithmic improvements enhance simulation stability.

Physical quantities can be reliably computed using this approach.

Abstract

Lattice QCD simulations at small lattice spacings and quark masses close to their physical values are technically challenging. In particular, the simulations can get trapped in the topological charge sectors of field space or may run into instabilities triggered by accidental near-zero modes of the lattice Dirac operator. As already noted in ref. [1], the first problem is bypassed if open boundary conditions are imposed in the time direction, while the second can potentially be overcome through twisted-mass determinant reweighting [2]. In this paper, we show that twisted-mass reweighting works out as expected in QCD with open boundary conditions and 2+1 flavours of O(a) improved Wilson quarks. Further algorithmic improvements are tested as well and a few physical quantities are computed for illustration.