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QCD phase structure at finite isospin chemical potential and smaller-than-physical quark mass

Bastian B. Brandt, Volodymyr Chelnokov, Francesca Cuteri, Gergely Endrődi

Abstract

Introduction of a nonzero isospin chemical potential in QCD leads to the emergence of a pion condensed phase at sufficiently large $μ_I$, bounded by a second order transition line. At zero temperature the pion condensate appears at $μ_I = m_π/ 2$. Recent numerical studies at physical quark masses show that the pion condensation boundary remains vertical up to the meeting point with the chiral crossover line. If this result remains valid when the light quark mass (and the pion mass) goes to zero, then in the chiral limit at temperatures below the chiral transition pion condensation happens at arbitrary nonzero $μ_I$. We report on results of a lattice QCD simulation of a 2+1 flavour QCD at nonzero isospin chemical potential, at smaller-than-physical light quark mass, that support this scenario.

QCD phase structure at finite isospin chemical potential and smaller-than-physical quark mass

Abstract

Introduction of a nonzero isospin chemical potential in QCD leads to the emergence of a pion condensed phase at sufficiently large , bounded by a second order transition line. At zero temperature the pion condensate appears at . Recent numerical studies at physical quark masses show that the pion condensation boundary remains vertical up to the meeting point with the chiral crossover line. If this result remains valid when the light quark mass (and the pion mass) goes to zero, then in the chiral limit at temperatures below the chiral transition pion condensation happens at arbitrary nonzero . We report on results of a lattice QCD simulation of a 2+1 flavour QCD at nonzero isospin chemical potential, at smaller-than-physical light quark mass, that support this scenario.

Paper Structure

This paper contains 4 sections, 6 equations, 2 figures.

Table of Contents

  1. Introduction
  2. Lattice simulation setup
  3. Reweighting
  4. Summary

Figures (2)

  • Figure 1: (left) Pion condensation phase at physical light quark mass (taken from muI-phys-plot). (right) Singular value densities at $T=132.24$ MeV, for three different values of $\mu_I$.
  • Figure 2: (left) Reweighting of the pion condensate in pion source $\lambda$ and final extrapolation of the reweighted improved condensate to $\lambda=0$. (right) The pion condensation boundary points obtained at $m_\pi = m_{\pi,\mathrm{phys}} / \sqrt{2}$.