SPECTRA OF PERTURBATIONS PRODUCED BY DOUBLE INFLATION WITH AN INTERMEDIATE MATTER-DOMINATED STAGE

The spectra of adiabatic perturbations generated in a realistic double-inflationary model with two massive scalar fields is calculated, including the case when m(h) >> m(l) and there exists an intermediate power-law regime a(t) is-proportional-to t2/3 between the two phases of inflation. In the latter case, the spectrum has a non-flat step-like behaviour in terms of the quantity k3/2 PHI(k) where PHI is a r.m.s. gravitational potential, with larger amplitude at large scales. Transition from the upper plateau to the lower one goes through a very short period of fall-off is-proportional-to k-3 (modulated by oscillations) followed by a k-1 behaviour and, finally, by a fall-off is-proportional-to k-5.5 until the lower plateau is reached. The spectrum of gravitational waves produced in this model is found, too. It has a different structure in the transition region between the two plateaus. Back reaction of generated inhomogeneities on the background is considered in the case of the power-law regime.