We examine the constraints on the construction of Fock spaces for scalar fields in spatially flat Robertson-Walker space-times imposed by requiring that the vacuum state of the theory have a two-point function possessing the Hadamard singularity structure required by standard renormalization theory. It is shown that any such vacuum state must be a second-order adiabatic vacuum. We discuss the global requirements on the two-point function for it to possess the Hadamard form at all times if it possesses it at one time.
|Original language||English (US)|
|Number of pages||7|
|Journal||Physical Review D|
|State||Published - 1985|
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)