QCD phase diagram for nonzero isospin-asymmetry

TL;DR

This study explores the QCD phase diagram under isospin asymmetry using advanced lattice simulations, revealing the absence of pion condensation above 160 MeV and linking deconfinement to BEC-BCS crossover at high asymmetries.

Contribution

It introduces a novel extrapolation method employing the singular value representation to study the QCD phase diagram with physical quark masses under isospin asymmetry.

Findings

No pion condensation above approximately 160 MeV.

Deconfinement crossover connects to BEC-BCS crossover at high isospin asymmetries.

Simulation results align with effective theories and models.

Abstract

The QCD phase diagram is studied in the presence of an isospin asymmetry using continuum extrapolated staggered quarks with physical masses. In particular, we investigate the phase boundary between the normal and the pion condensation phases and the chiral/deconfinement transition. The simulations are performed with a small explicit breaking parameter in order to avoid the accumulation of zero modes and thereby stabilize the algorithm. The limit of vanishing explicit breaking is obtained by means of an extrapolation, which is facilitated by a novel improvement program employing the singular value representation of the Dirac operator. Our findings indicate that no pion condensation takes place above $T\approx 160$ MeV and also suggest that the deconfinement crossover continuously connects to the BEC-BCS crossover at high isospin asymmetries. The results may be directly compared to effective theories and model approaches to QCD.