Quantized first-order phase transition and two sets of critical end point in droplet quark matter

TL;DR

This paper studies how finite-size effects influence the chiral phase transition in quark matter, revealing a quantized first-order transition and two critical end points due to zero-mode dominance in small systems.

Contribution

It introduces a finite-size analysis of the chiral phase transition using the NJL model, highlighting the emergence of a quantized transition and multiple critical end points.

Findings

Finite-size effects cause the chiral transition to split into two first-order transitions.

Zero-mode dominance leads to a quantized first-order phase transition.

Two sets of critical end points appear in the phase diagram.

Abstract

The finite-size effect on the chiral phase transition is investigated in the Nambu--Jona-Lasinio model. To take into account finite-size effects, momentum integrals are replaced by momentum summations. The ground state of quark matter at finite size is favored when applying the periodic spatial boundary condition for quarks. The zero-momentum contribution is taken into account in the periodic boundary condition, and its contribution becomes important when the system size is comparable with the pion wavelength. When the zero-mode contribution becomes dominant, the conventional first-order chiral phase transition at high baryon chemical potential splits into two first-order phase transitions in small system of quark matter, and two sets of critical end point show up in the temperature and chemical potential plane.