STRUCTURE OF PRIMORDIAL GRAVITATIONAL-WAVES SPECTRUM IN A DOUBLE INFLATIONARY MODEL

The gravitational waves (GW) background generated in a double inflatio nary model, with two scalar fields mutually interacting through gravit y only, and its relative contribution T/S to large-angle temperature f luctuations of the relic microwave background are investigated in deta il. The relation between T/S and the slope of the GW spectrum n(T) is shown to be a discriminative test between a slow-roll inflation driven by one scalar field and more complicated models. It is found that the GW amplitude is not exactly zero in minima of spectral oscillations, this property being an observational, in principle, manifestation of G W being in a squeezed vacuum state during inflation.