Quantum decay of domain walls in cosmology .2. Hamiltonian approach

This paper studies the decay of a large, closed domain wall in a closed universe. Such walls can form in the presence of a broken, discrete symmetry. We study a novel process of quantum decay for such a wall, in which the vacuum fluctuates from one discrete state to another throughout one-half of the universe, so that the wall decays into pure field energy. Equivalently, the fluctuation can be thought of as the nucleation of a second closed domain wall of zero size, followed by its growth by quantum tunneling and its collision with the first wall, annihilating both. We therefore study the two-wall system coupled to a spherically symmetric gravitational field. We derive a simple form of the two-wall action, use Dirac quantization, obtain the two-wall wave function for annihilation, find from it the barrier factor for this quantum tunneling, and thereby get the decay probability. This is the second paper of a series. [S0556-2821(97)07120-8].