Dynamical Theory of Phase Transitions and Topological Defect Formation in the Early Universe

摘要

We review the current issues of nonequilibrium phase transitions, inparticular, in the early universe. Phase transitions cannot maintain thermalequilibrium and become nonequilibrium when the thermal relaxation time scale isgreater than the dynamical time scale. Nonequilibrium phase transitions wouldhave happened in certain evolution stages of the early universe because therapid expansion quenched matter fields. We apply the recently introducedLiouville-von Neumann method, another canonical method, to nonequilibrium phasetransitions in the Minkowski spacetime and find the scaling behavior of domainsizes. Topological defects are thus determined by the dynamical processes ofnonequilibrium phase transitions. However, the expansion of the universefreezes domain growth in the comoving frame and thus leads to a scale-invariantdomain size. We also discuss the physical implications of nonequilibrium phasetransitions in the early universe.