Relativistic hydrodynamics with spinodal decomposition

TL;DR

This work develops a covariant relativistic hydrodynamic framework that incorporating spinodal decomposition to model phase separation during first-order transitions in QCD matter. By adding a gradient (surface-tension) term with coefficient $K$, the authors modify the stress-energy tensor and baryon current, and they close the system with an equation of state that matches lattice results at zero baryon chemical potential while extending into metastable regions. They specialize to Bjorken flow to derive and solve the reduced equations for energy density and baryon density, comparing $K=0$ and $K=5\times10^{-5}$ MeV$^{-4}$, with an EOS that interpolates between perturbative QCD and hadron gas and includes a critical point. The results illustrate how spinodal surface terms imprint persistent structure as the system traverses the coexistence region, providing a tool to study signatures of a first-order transition in heavy-ion collisions and neutron star mergers.

Abstract

We introduce the equations of relativistic hydrodynamics that incorporate phase separation via spinodal decomposition. These equations consider surface effects between the two phases and are applicable for simulating intermediate-energy heavy-ion collisions and binary neutron star mergers, where a first-order phase transition is expected. We solve these equations in the context of Bjorken flow, which offers the relevant geometric framework for ion collisions.

Figures (3)

• Figure 1: System phase at different spacetime points.
• Figure 2: Baryon density evolution at different times. From top to bottom, curves correspond to $\tau =10$ fm, 10.5 fm, 11.5 fm, 12.5 fm and 13.5 fm.
• Figure 3: Energy density evolution at two different values of $\tau$.