The Sign Problem via Imaginary Chemical Potential

TL;DR

This paper investigates the sign problem in lattice QCD by analyzing the average phase factor at imaginary chemical potential, confirming analytical predictions and highlighting the role of low-lying Dirac eigenvalues.

Contribution

It provides lattice calculations of the average phase factor at imaginary chemical potential, aligning with analytical results and emphasizing the significance of the lowest-lying Dirac eigenvalues.

Findings

Lattice results agree with analytical predictions in the microscopic regime.

The average phase factor is dominated by the lowest-lying Dirac eigenvalues.

Results hold for both quenched and phase-quenched QCD.

Abstract

We calculate an analogue of the average phase factor of the staggered fermion determinant at imaginary chemical potential. Our results from the lattice agree well with the analytical predictions in the microscopic regime for both quenched and phase-quenched QCD. We demonstrate that the average phase factor in the microscopic domain is dominated by the lowest-lying Dirac eigenvalues.