Critical point and Bose-Einstein condensation in pion matter

TL;DR

This paper investigates the phase transition and Bose-Einstein condensation in interacting pion matter using phenomenological models, revealing an intersection of critical phenomena at a critical end point.

Contribution

It introduces two phenomenological models for pion matter and demonstrates their qualitative and quantitative agreement in describing phase transitions and Bose-Einstein condensation.

Findings

Models fit lattice QCD data on pion condensate density.

Both models show similar thermodynamic behavior.

Bose-Einstein condensation line intersects with the first order phase transition line.

Abstract

The Bose-Einstein condensation and the liquid-gas first order phase transition are studied in the interacting pion matter. Two phenomenological models are used: the mean-field model and the hybrid model. Free model parameters are fixed by fitting the lattice QCD data on the pion Bose condensate density at zero temperature. In spite of some minor differences the two model demonstrate an identical qualitative and very close quantitative behavior for the thermodynamic functions and electric charge fluctuations. A peculiar property of the considered models is an intersection of the Bose-Einstein condensation line and the line of the first order phase transition at the critical end point.