Phase conversion in a weakly first-order quark-hadron transition

TL;DR

This paper studies the phase conversion process in a weakly first-order quark-hadron transition, combining lattice QCD and resonance gas models to analyze nucleation and spinodal decomposition, with implications for cosmology and heavy-ion collisions.

Contribution

It presents a detailed numerical analysis of bubble nucleation and phase conversion mechanisms in a weakly first-order transition, highlighting the dominance of spinodal decomposition over nucleation.

Findings

Nucleation dominates in cosmological scenarios with high expansion rates.

Spinodal decomposition is the main mechanism at lower expansion rates.

Results differ from strongly first-order transition models like the MIT bag model.

Abstract

We investigate the process of phase conversion in a thermally-driven {\it weakly} first-order quark-hadron transition. This scenario is physically appealing even if the nature of this transition in equilibrium proves to be a smooth crossover for vanishing baryonic chemical potential. We construct an effective potential by combining the equation of state obtained within Lattice QCD for the partonic sector with that of a gas of resonances in the hadronic phase, and present numerical results on bubble profiles, nucleation rates and time evolution, including the effects from reheating on the dynamics for different expansion scenarios. Our findings confirm the standard picture of a cosmological first-order transition, in which the process of phase conversion is entirely dominated by nucleation, also in the case of a weakly first-order transition. On the other hand, we show that, even for expansion rates much lower than those expected in high-energy heavy ion collisions, nucleation is very unlikely, indicating that the main mechanism of phase conversion is spinodal decomposition. Our results are compared to those obtained for a strongly first-order transition, as the one provided by the MIT bag model.