Abstract
We investigate the process of phase conversion in a thermally driven 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.
Highlights
It is widely accepted that experiments in high-energy heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) have produced clear signals that nuclear matter undergoes a phase transition to a deconfined partonic phase at sufficiently large values of energy density [1, 2]
Using two different equations of state, a realistic matching of hadron gas of resonances and Lattice quantum chromodynamics (QCD) for Nf = 2 + 1 on one side, and the bag model on the other, we calculated both static and dynamical features of homogeneous bubble nucleation in a weakly first-order quark-hadron transition scenario, which is physically appealing if one takes into account results from the lattice and from experiments, as well as the nonequilibrium nature of the phase conversion process, especially in the case of high-energy heavy ion collisions
This indicates that an adequate approach to the dynamics of nucleation away from Tc should take into account exact bubble profiles φ(r), which in general have to be calculated numerically
Summary
It is widely accepted that experiments in high-energy heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) have produced clear signals that nuclear matter undergoes a phase transition to a deconfined partonic phase at sufficiently large values of energy density [1, 2]. Most hydrodynamic calculations within high-energy heavy ion collisions adopt an equation of state which provides a strongly first-order transition [1] Another point that is seldom mentioned is that, being built on equilibrium assumptions, Lattice QCD thermodynamics does not provide any information on the dynamical nature of the deconfining transition. Bubble nucleation is one of different simplified mechanisms used to describe the dynamics of a first-order phase transition [8] In this kind of transition, for temperatures slightly lower than the critical temperature, Tc, the thermodynamic potential exhibits a metastable minimum besides the global minimum. 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.
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