Practical approach to the sign problem at finite theta-vacuum angle

TL;DR

This paper proposes a practical method to mitigate the sign problem in lattice QCD simulations at finite theta-vacuum angles by using the PNJL model and reweighting techniques, minimizing the P-odd mass term.

Contribution

It introduces a novel approach combining the PNJL model and reweighting to effectively address the sign problem in finite theta QCD simulations.

Findings

Identified a good reference system for reweighting in the PNJL model.

Estimated the average reweighting factor to validate the approach.

Demonstrated potential to improve lattice QCD simulations at finite theta.

Abstract

We investigate a way of circumventing the sign problem in lattice QCD simulations with a theta-vacuum term, using the PNJL model. We consider the reweighting method for the QCD Lagrangian after the U_A(1) transformation. In the Lagrangian, the P-odd mass term as a cause of the sign problem is minimized. In order to find out a good reference system in the reweighting method, we estimate the average reweighting factor by using the two-flavor PNJL model and eventually find a good reference system.