Spontaneous parity breaking, gauge coupling unification, and consistent cosmology with transitory domain walls

Abstract

The formation of transitory domain walls is quite generic in theories with spontaneous breaking of discrete symmetries. Since these walls are in conflict with cosmology, there has to be some mechanism which makes them disappear. We study one such mechanism by incorporating Planck-scale suppressed operators within the framework of left-right symmetric models where left-right parity (D parity) is spontaneously broken. We find that this mechanism cannot make the walls disappear in minimal versions of left-right symmetric models. We propose two viable extensions of this model and show that Planck-scale suppressed operators can give rise to the successful disappearance of domain walls provided the scale of parity breaking obeys certain limits. We also constrain the scale of parity breaking by demanding successful gauge-coupling unification and make a comparison of the unification and cosmology bounds.