Talk abstract details

We remind and precise the notion of creatable universe which has recently appeared in the literature.

We consider the FRW universes with positive or zero 3-space curvature, and allow for small scalar and tensor perturbations. In the first case of a positive 3-space curvature, it is easily seen that the resulting universes are creatable universes, as it was to be expected if the notion of creatable universe is to make sense. In the second case of vanishing 3-space curvature, we show how the power spectrum of some time decaying modes must behave in order to guaranty the creativeness of the considered universe.

The above creativeness makes severe restrictions to a possible anisotropy of the above perturbations. We consider the creativeness of some of these anisotropic universes, which have been considered recently in the literature in order to explain some cosmic observations, among them some observed features of the CMB spectrum.