Finite density lattice QCD without extrapolations

TL;DR

This paper demonstrates a method to study finite density lattice QCD directly in the canonical formulation using physical quark masses, avoiding unreliable extrapolations in chemical potential.

Contribution

It introduces a canonical approach to finite density lattice QCD with physical quark masses, enabling direct access to baryon and strangeness densities without extrapolation.

Findings

Computed QCD pressure as a function of baryon and strangeness densities.

Determined chemical potentials corresponding to various densities.

Validated the canonical formulation with high-statistics simulations.

Abstract

Finite density lattice QCD usually relies on extrapolations in baryon chemical potential ($\mu_B$), be it Taylor expansion, T' expansion (\cite{Borsanyi:2021sxv}) or analytical continuation. However, their range of validity is difficult to control. In the canonical formulation, the baryon density is the parameter of the system, not $\mu_B$. Here we demonstrate that we can access finite density QCD in the canonical formulation with physical quark masses. We present first results with both the strangeness ($n_S$) and baryon ($n_B$) densities as parameters. Specifically, we compute the QCD pressure and chemical potentials as functions of $n_B$ and $n_S$. Our computations rely on high-statistics simulations with 2+1 4HEX-staggered fermions.