The taming of the alpha-vacuum
  When examining a field theory in a general state, the propagator must be made consistent with that state and new counterterms are allowed if the state breaks some of the space-time's symmetries. This talk describes the specific example of how the propagator for the alpha-vacua of de Sitter space must become the Green's function for two antipodal sources to obtain a renormalizable theory. 
Hael Collins (Carnegie Mellon University and University of   Massachusetts, Amherst)