Phase transition dynamics for baryon-dense matter

TL;DR

This paper models the phase transition dynamics in baryon-rich matter, analyzing interface properties and unstable modes to assess the potential for spinodal decomposition in nuclear collisions.

Contribution

It introduces a simple two-phase equation of state with finite-range effects and studies the interface tension and unstable modes relevant to phase separation.

Findings

Estimate of interface tension between phases

Derivation of dispersion relation for unstable modes

Discussion on optimizing collision conditions for spinodal decomposition

Abstract

We construct a simple two-phase equation of state intended to resemble that of compressed baryon-rich matter and then introduce a gradient term in the compressional energy density to take account of fintie-range effects in non-uniform configurations. With this model we study the interface between the two coexisting phases and obtain estimates for the associated interface tension. Subsequently, we incorporate the finite-range equation of state into ideal or viscous fluid dynamics and derive the collective dispersion relation for the mechanically unstable modes of bulk matter in the spinodal region of the thermodynamic phase diagram. Combining these results with time scales extracted from existing dynamical transport simulations, we discuss the prospects for spinodal phase separation to occur in nuclear collisions. We argue that these can be optimized by a careful tuning of the collision energy to maximize the time spent by the bulk of the system inside the mechanically unstable spinodal region of the phase diagram. Our specific numerical estimates suggest cautious optimism that this phenomenon may in fact occur, though a full dynamical simulation is needed for a detailed assessment.