Cosmological evolution of a ghost scalar field

Abstract

We consider a scalar field with a negative kinetic term minimally coupled to gravity. We obtain an exact non-static spherically symmetric solution which describes a wormhole in a cosmological setting. The wormhole is shown to connect two homogeneous spatially flat universes expanding with acceleration. Depending on the wormhole's mass parameter m the acceleration can be constant (the de Sitter case) or infinitely growing.