  We set up a consistent renormalizable perturbation theory of a scalar field
in a nontrivial alpha vacuum in de Sitter space. Although one representation of
the effective action involves non-local interactions between anti-podal points,
we show the theory leads to causal physics, and we prove a spectral theorem for
the interacting two-point function. We construct the renormalized stress energy
tensor and show this develops no imaginary part at leading order in the
interactions, consistent with stability.
