Taming the alpha-vacuum

By Hael Collins, Carnegie Mellon University

The invariant alpha-vacuum states of de Sitter space provide a tool for examining the sensitivity of the cosmic microwave background to initial state effects in inflation. In an interacting scalar theory, these states lead to apparent non-renormalizable divergences in the loop corrections. In this talk, I shall show that these divergences are removed by modifying the propagator to be the Green's function associated with point source and its image. This setting serves as an example of the more general problem of describing the propagation of a field theory from an initially defined state, whether in a flat or an expanding background.