Lattice QCD at finite isospin density and/or temperature

TL;DR

This paper investigates the phase transitions of two-flavour lattice QCD at finite isospin density and temperature, identifying crossover and phase transition behaviors, including superfluid and quark-gluon plasma phases, using numerical simulations.

Contribution

It provides new insights into the phase structure of lattice QCD at finite isospin chemical potential and temperature, including the nature of phase transitions and effects of 4-fermion interactions.

Findings

Determined the crossover line from hadronic matter to quark-gluon plasma at small $I$.

Observed the superfluid pion-condensed phase transitioning to quark-gluon plasma at larger $I$.

Identified the change from second to first order phase transition as $I$ increases.

Abstract

We simulate two-flavour lattice QCD with at a finite chemical potential $\mu_I$ for isospin, and finite temperature. At small $\mu_I$, we determine the position of the crossover from hadronic matter to a quark-gluon plasma as a function of $\mu_I$. At larger $\mu_I$ we observe the phase transition from the superfluid pion-condensed phase to a quark-gluon plasma, noting its change from second order to first order as $\mu_I$ is increased. We also simulate two-flavour lattice QCD at zero quark mass, using an action which includes an additional 4-fermion interaction, at temperatures close to the chiral transition on $N_t=8$ lattices.