The first order phase transition of a vacuum and baryon-number domain structure of the universe

If CP-nonconservation arises from spontaneous symmetry breaking in the very early universe, the universe will have a domain structure of baryon number. A model of the early universe is proposed in which domains are stretched exponentially and the radius of the domains is much greater than that of the standard big bang model, provided that the GUT phase transition is of first order. If the size of the stretched domains is sufficiently big to avoid pair annihilations of baryon and antibaryon domains, the difficulties of the baryon symmetric universe may be removed.