We study the cosmological consequences of spontaneous breaking of an approximate discrete symmetry. The breaking leads to the formation of protodomains of false and true vacuums separated by domain walls of thicknesses determined by the mass scale of the model. The cosmological evolution of the walls is extremely sensitive to the magnitude of the biasing; several scenarios are possible, depending on the interplay between the surface tension on the walls and the volume pressure from the biasing. Walls may disappear almost immediately after they form, or may live long enough to dominate the energy density of the Universe and cause power-law inflation. We obtain limits on the biasing that characterize each possible scenario.

• Received 24 October 1988

DOI:https://doi.org/10.1103/PhysRevD.39.1558