Dense $\textrm{QCD}_2$ with matrix product states

TL;DR

This paper applies matrix product states and DMRG to study one-flavor lattice QCD in 1+1 dimensions at zero temperature and finite density, revealing inhomogeneous phases and the transition from hadronic to quark degrees of freedom.

Contribution

It introduces a novel application of tensor network methods to lattice QCD in low dimensions, exploring phase structure and inhomogeneity at finite density.

Findings

Identification of inhomogeneous chiral condensate phases

Observation of baryon crystal formation at nonzero density

Analysis of the transition from hadronic to quark matter

Abstract

We study one-flavor $\mathrm{SU}(2)$ and $\mathrm{SU}(3)$ lattice QCD in ($1+1$) dimensions at zero temperature and finite density using matrix product states and the density matrix renormalization group. We compute physical observables such as the equation of state, chiral condensate, and quark distribution function as functions of the baryon number density. As a physical implication, we discuss the inhomogeneous phase at nonzero baryon density, where the chiral condensate is inhomogeneous, and baryons form a crystal. We also discuss how the dynamical degrees of freedom change from hadrons to quarks through the formation of quark Fermi seas.