Professor Pedro Ferreira

Abstract:

To obtain further estimates of several cosmological parameters, the recent BOOMERANG-98 (B98) and MAXIMA-1 cosmic microwave background (CMB) anisotropy data, as well as COBE DMR, were analyzed. The resulting data support the chief predictions of the inflation paradigm, that the geometry of the Universe is flat, and that the initial density perturbations are scale invariant, and with the corollary that the density of mass energy in the Universe is dominated by a form other than ordinary matter.

Abstract:

We reexamine Wald's no-hair theorem for global anisotropy in the brane world scenarios. We derive a set of sufficient conditions which must be satisfied by the brane matter and bulk metric so that a homogeneous and anisotropic brane asymptotically evolves to a de Sitter spacetime in the presence of a positive cosmological constant on the brane. We discuss the violations of these sufficient conditions and we show that a negative nonlocal energy density or the presence of strong anisotropic stress (i.e., a magnetic field) may lead the brane to collapse. We discuss the generality of these conditions.