Pion condensation at lower than physical quark masses

TL;DR

This paper investigates pion condensation in QCD at lower than physical quark masses, exploring how the Bose-Einstein Condensation boundary shifts towards the chiral limit through lattice simulations.

Contribution

It provides the first lattice simulation results of the BEC transition at half the physical quark masses, comparing with the physical point to understand chiral limit effects.

Findings

BEC transition occurs at lower isospin chemical potential at reduced quark masses.

The BEC boundary shifts closer to zero chemical potential as quark masses decrease.

Results suggest the chiral limit significantly influences the phase transition boundary.

Abstract

In QCD at large enough isospin chemical potential Bose-Einstein Condensation (BEC) takes place, separated from the normal phase by a phase transition. From previous studies the location of the BEC line at the physical point is known. In the chiral limit the condensation happens already at infinitesimally small isospin chemical potential for zero temperature according to chiral perturbation theory. The thermal chiral transition at zero density might then be affected, depending on the shape of the BEC boundary, by its proximity. As a first step towards the chiral limit, we perform simulations of 2+1 flavors QCD at half the physical quark masses. The position of the BEC transition is then extracted and compared with the results at physical masses.