3 research outputs found
Primordial perturbations in a non singular bouncing universe model
We construct a simple non singular cosmological model in which the currently
observed expansion phase was preceded by a contraction. This is achieved, in
the framework of pure general relativity, by means of a radiation fluid and a
free scalar field having negative energy. We calculate the power spectrum of
the scalar perturbations that are produced in such a bouncing model and find
that, under the assumption of initial vacuum state for the quantum field
associated with the hydrodynamical perturbation, this leads to a spectral index
n=-1. The matching conditions applying to this bouncing model are derived and
shown to be different from those in the case of a sharp transition. We find
that if our bounce transition can be smoothly connected to a slowly contracting
phase, then the resulting power spectrum will be scale invariant.Comment: 11 pages, RevTeX 4, 8 figures, submitted to Phys. Rev.
G1 Cosmologies with Gravitational and Scalar Waves
I present here a new algorithm to generate families of inhomogeneous massless
scalar field cosmologies. New spacetimes, having a single isometry, are
generated by breaking the homogeneity of massless scalar field models
along one direction. As an illustration of the technique I construct
cosmological models which in their late time limit represent perturbations in
the form of gravitational and scalar waves propagating on a non-static
inhomogeneous background. Several features of the obtained metrics are
discussed, such as their early and late time limits, structure of singularities
and physical interpretation.Comment: 24 pages, 2 figure