3.4 Nucleosynthesis3 RELATIVISTIC COSMOLOGY3.2 Inflation

3.3 Quark-Hadron Phase Transition 

The standard picture of cosmology assumes that a phase transition (associated with chiral symmetry breaking after the electroweak transition) occurred at approximately image seconds after the Big Bang to convert a plasma of free quarks and gluons into hadrons. Although this transition can be of significant cosmological importance, it is not known with certainty whether it is of first order or higher, and what the astrophysical consequences might be on the subsequent state of the Universe. For example, the transition may give rise to significant baryon number inhomogeneities which can influence the outcome of primordial nucleosynthesis as evidenced in the distribution and averaged light element abundances. The QCD transition and baryon inhomogeneities may also play a significant and potentially observable role in the generation of primordial magnetic fields.

Rezolla et al. [47] considered a first order phase transition and the nucleation of hadronic bubbles in a supercooled quark-gluon plasma, solving the relativistic Lagrangian equations for disconnected and evaporating quark regions during the final stages of the phase transition. They numerically investigated a single isolated quark drop with an initial radius large enough so that surface effects can be neglected. The droplet evolves as a self-similar solution until it evaporates to a sufficiently small radius that surface effects break the similarity solution and increase the evaporation rate. Their simulations indicate that, in neglecting long-range energy and momentum transfer (by electromagnetically interacting particles) and assuming that the baryon number is transported with the hydrodynamical flux), the baryon number concentration is similar to what is predicted by chemical equilibrium calculations.

Kurki-Suonio and Laine [37] studied the growth of bubbles and the decay of droplets using a spherically symmetric code that accounts for a phenomenological model of the microscopic entropy generated at the phase transition surface. Incorporating the small scale effects of the finite wall width and surface tension, but neglecting entropy and baryon flow through the droplet wall, they demonstrate the dynamics of nucleated bubble growth and quark droplet decay. They also find that evaporating droplets do not leave behind a global rarefaction wave to dissipate any previously generated baryon number inhomogeneity.

3.4 Nucleosynthesis3 RELATIVISTIC COSMOLOGY3.2 Inflation

image Computational Cosmology: from the Early Universe to the Large Scale Structure
Peter Anninos
© Max-Planck-Gesellschaft. ISSN 1433-8351
Problems/Comments to livrev@aei-potsdam.mpg.de