A new possible quark-hadron mixed phase in protoneutron stars

TL;DR

This paper proposes a novel mixed phase of quark and hadronic matter in protoneutron stars, enabled by lepton number conservation during neutrino trapping, which could influence star evolution and observable signals.

Contribution

It introduces a new type of quark-hadron mixed phase in hot, lepton-rich matter, differing from cold matter by considering global lepton number conservation.

Findings

A new mixed phase with non-constant pressure can exist during neutrino trapping.

The mixed phase consists of spherical drops and bubbles without Coulomb lattice formation.

Disappearance of the mixed phase may cause delayed star collapse and neutrino/gravitational wave emissions.

Abstract

The phase transition from hadronic matter to quark matter at high density might be a strong first order phase transition in presence of a large surface tension between the two phases. While this implies a constant-pressure mixed phase for cold and catalyzed matter this is not the case for the hot and lepton rich matter formed in a protoneutron star. We show that it is possible to obtain a mixed phase with non-constant pressure by considering the global conservation of lepton number during the stage of neutrino trapping. In turn, it allows for the appearance of a new kind of mixed phase as long as neutrinos are trapped and its gradual disappearance during deleptonization. This new mixed phase, being composed by two electric neutral phases, does not develop a Coulomb lattice and it is formed only by spherical structures, drops and bubbles, which can have macroscopic sizes. The disappearance of the mixed phase at the end of deleptonization might lead to a delayed collapse of the star into a more compact configuration containing a core of pure quark phase. In this scenario, a significant emission of neutrinos and, possibly, gravitational waves are expected.