Anatomy of the sign-problem in heavy-dense QCD

TL;DR

This paper investigates the sign problem in heavy-dense QCD at finite chemical potential using the density-of-states method, providing high-precision calculations and insights into phase behavior and symmetries.

Contribution

It offers the first high-precision calculation of the phase factor expectation in heavy-dense QCD and compares results with reweighting methods to analyze the sign problem.

Findings

Confirmed particle-hole symmetry at low temperatures

Identified a strong sign problem at intermediate chemical potentials

Discovered an inverse Silver Blaze phenomenon near the onset chemical potential

Abstract

QCD at finite densities of heavy quarks is investigated using the density-of-states method. The phase factor expectation value of the quark determinant is calculated to unprecedented precision as a function of the chemical potential. Results are validated using those from a reweighting approach where the latter can produce a significant signal-to-noise ratio. We confirm the particle-hole symmetry at low temperatures, find a strong sign problem at intermediate values of the chemical potential, and an inverse Silver Blaze feature for chemical potentials close to the onset value: here, the phase quenched theory underestimates the density of the full theory.