Composite reweighting with Imaginary Chemical Potentials in SU(3)

TL;DR

This paper reviews the overlap issues in reweighting methods for finite density QCD and proposes using imaginary chemical potentials to build unbiased polynomial expansions for the Grand Canonical Partition function.

Contribution

It introduces a novel approach of constructing an unbiased polynomial expansion via parallel ensembles with imaginary chemical potentials, addressing overlap pathology.

Findings

Identifies systematic bias in reweighting methods due to overlap issues.

Proposes a series of parallel ensembles with imaginary chemical potentials to mitigate bias.

Contrasts this approach with secondary reweighting techniques.

Abstract

We review the overlap pathology of the Glasgow reweighting method for finite density QCD, and discuss the sampling bias that effects the determination of the ensemble-averaged fugacity polynomial expansion coefficients that form the Grand Canonical Partition function. The expectation of the difference in free energies between canonical partition functions generated with different measures is presented as an indicator of a systematic quark number dependent biasing in the reweighting approach. The advantages of building up an unbiased polynomial expansion for the Grand Canonical Partition function through a series of parallel ensembles generated by reweighting with imaginary chemical potentials are then contrasted with addressing the overlap pathology through a secondary reweighting.