PHASE-TRANSITIONS OUT OF EQUILIBRIUM - DOMAIN FORMATION AND GROWTH

We study the dynamics of phase transitions out of equilibrium in weakly coupled scalar field theories. We consider the case in which there is a rapid supercooling from an initial symmetric phase in thermal equilibrium at temperature T(i) > T(c) to a final state at low temperature T(f) almost-equal-to 0. In particular we study the formation and growth of correlated domains out of equilibrium. It is shown that the dynamics of the process of domain formation and growth (spinodal decomposition) cannot be studied in perturbation theory, and a nonperturbative self-consistent Hartree approximation is used to study the long time evolution. We find in weakly coupled theories that the size of domains grows at long times as xi(D)(t) almost-equal-to square-root txi(0). The size of the domains and the amplitude of the fluctuations grow up to a maximum time t(s) which in weakly coupled theories is estimated to be [GRAPHICS] with xi(0) the zero-temperature correlation length. For very weakly coupled theories, their final size is several times the zero-temperature correlation length. For strongly coupled theories the final size of the domains is comparable to the zero-temperature correlation length and the transition proceeds faster.