Re: Tipler's Conjectures

From: Amara Graps (
Date: Sun May 06 2001 - 08:43:49 MDT

More information for the discussion.

General Relativity and Quantum Cosmology, abstract

From: "Marcelo J. Reboucas" <>
Date: Wed, 2 May 2001 00:49:39 GMT (147kb)

Detectability of Cosmic Topology in Almost Flat Universes

Authors: G.I. Gomero, M.J. Reboucas, R. Tavakol
Comments: 18 pages, 3 figures, LaTeX2e

     Recent observations suggest that the ratio of the total density to
     the critical density of the universe, $\Omega_0$, is likely to be
     very close to one, with a significant proportion of this energy
     being in the form of a dark component with negative pressure.
     Motivated by this result, we study the question of observational
     detection of possible non-trivial topologies in universes with
     $\Omega_0 \sim 1$, which include a cosmological constant. Using a
     number of indicators we find that as $\Omega_0 \to 1$, increasing
     families of possible topologies become either undetectable or can
     be excluded observationally. Furthermore, given a non-zero lower
     bound on $|\Omega_0 - 1|$, we can rule out families of topologies
     as possible candidates for the shape of our universe. We
     demonstrate these findings concretely by considering families of
     topologies and employing bounds on cosmological parameters from
     recent observations. We find that given the present bounds on
     cosmological parameters, there are families of both hyperbolic and
     spherical manifolds that remain undetectable and families that can
     be excluded as the shape of our universe. These results are of
     importance in future search strategies for the detection of the
     shape of our universe, given that there are an infinite number of
     theoretically possible topologies and that the future observations
     are expected to put a non-zero lower bound on $|\Omega_0 - 1|$
     which is more accurate and closer to zero.

Paper: Source (147kb), PostScript, or Other formats


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