an:00006822
Zbl 0749.46045
L??ders, Christian; Roberts, John E.
Local quasiequivalence and adiabatic vacuum states
EN
Commun. Math. Phys. 134, No. 1, 29-63 (1990).
00156104
1990
j
46N50 81T20
determining the physically relevant states; curved spacetime; local quasiequivalence class; Klein-Gordon field; Robertson-Walker spacetime; adiabatic vacuum state
Summary: The problem of determining the physically relevant states acquires a new dimension in curved spacetime where there is, in general, no natural definition of a vacuum state. It is argued that there is a unique local quasiequivalence class of physically relevant states and it is shown how this class can be specified for the free Klein-Gordon field on a Robertson-Walker spacetime by using the concept of an adiabatic vacuum state. Any two adiabatic vacuum states of order two are locally quasiequivalent.