Lattice-based QCD equation of state at finite baryon density: Cluster Expansion Model

TL;DR

This paper introduces a Cluster Expansion Model for the QCD equation of state at finite baryon density, accurately fitting lattice data using only two Fourier coefficients derived from simulations.

Contribution

The novel aspect is the development of a closed-form analytic model based on minimal lattice inputs, enabling precise descriptions at various baryon chemical potentials.

Findings

Excellent fit to lattice data at zero and imaginary chemical potential

Fourier coefficients can be reconstructed from baryon number susceptibilities

Model provides a practical analytic tool for QCD thermodynamics

Abstract

The QCD equation of state at finite baryon density is studied in the framework of a Cluster Expansion Model (CEM), which is based on the fugacity expansion of the net baryon density. The CEM uses the two leading Fourier coefficients, obtained from lattice simulations at imaginary $\mu_B$, as the only model input and permits a closed analytic form. Excellent description of the available lattice data at both $\mu_B = 0$ and at imaginary $\mu_B$ is obtained. We also demonstrate how the Fourier coefficients can be reconstructed from baryon number susceptibilities.