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What do very nearly flat detectable cosmic topologies look like?

B Mota1, G I Gomero2, M J Rebouças1 and R Tavakol3

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Recent studies of the detectability of the cosmic topology of nearly flat universes have often concentrated on the range of values of Ω0 given by current observations. Here we study the consequences of taking a range of bounds satisfying |Ω0 − 1| Lt 1, which include those expected from future observations such as the Planck mission, as well as those predicted by inflationary models. We show that in this limit, a generic detectable non-flat manifold is locally indistinguishable from either a cylindrical ({\bb R}^2 \times {\bb S}^1) or toroidal ({\bb R} \times {\bb T}^2) manifold, irrespective of its global shape, with the former being more likely. Importantly, this is compatible with some recent indications of the alignment of the quadrupole and octupole moments, based on the analysis of the first year WMAP data. It also implies that in this limit an observer would not be able to distinguish topologically whether the universe is spherical, hyperbolic or flat. By severely restricting the expected topological signatures of detectable isometries, our results provide an effective theoretical framework for interpreting cosmological observations, and can be used to confine the parameter spaces which realistic search strategies, such as the 'circles in the sky' method, need to concentrate on.


PACS

98.80.Jk Mathematical and relativistic aspects of cosmology

98.80.Es Observational cosmology (including Hubble constant, distance scale, cosmological constant, early Universe, etc)

02.40.-k Geometry, differential geometry, and topology

MSC

83F05 Cosmology

85A40 Cosmology (For relativistic cosmology, see 83F05)

Subjects

Mathematical physics

Gravitation and cosmology

Astrophysics and astroparticles

Dates

Issue 14 (21 July 2004)

Received 19 December 2003

Published 18 June 2004



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