CMB observations in LTB universes: Part I. Matching peak positions in the CMB spectrum

Acoustic peaks in the spectrum of the cosmic microwave background in spherically symmetric inhomogeneous cosmological models are studied. At the photon-baryon decoupling epoch, the universe may be assumed to be dominated by non-relativistic matter, and thus we may treat radiation as a test field in...

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Bibliographic Details
Published in:Journal of cosmology and astroparticle physics 2010-07, Vol.2010 (7), p.012-12
Main Authors: Yoo, Chul-Moon, Nakao, Ken-ichi, Sasaki, Misao
Format: Article
Language:English
Subjects:
APPROXIMATIONS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BARYONS
COSMOLOGICAL CONSTANT
COSMOLOGICAL MODELS
COSMOLOGY
DE SITTER SPACE
DECOUPLING
MATHEMATICAL SOLUTIONS
NONLUMINOUS MATTER
RED SHIFT
RELATIVISTIC RANGE
RELICT RADIATION
UNIVERSE
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Summary:Acoustic peaks in the spectrum of the cosmic microwave background in spherically symmetric inhomogeneous cosmological models are studied. At the photon-baryon decoupling epoch, the universe may be assumed to be dominated by non-relativistic matter, and thus we may treat radiation as a test field in the universe filled with dust which is described by the Lemaitre-Tolman-Bondi (LTB) solution. First, we give an LTB model whose distance-redshift relation agrees with that of the concordance Delta *LCDM model in the whole redshift domain and which is well approximated by the Einstein-de Sitter universe at and before decoupling. We determine the decoupling epoch in this LTB universe by Gamow's criterion and then calculate the positions of acoustic peaks. Thus obtained results are not consistent with the WMAP data. However, we find that one can fit the peak positions by appropriately modifying the LTB model, namely, by allowing the deviation of the distance-redshift relation from that of the concordance Delta *LCDM model at z > 2 where no observational data are available at present. Thus there is still a possibility of explaining the apparent accelerated expansion of the universe by inhomogeneity without resorting to dark energy if we abandon the Copernican principle. Even if we do not take this extreme attitude, it also suggests that local, isotropic inhomogeneities around us may seriously affect the determination of the density contents of the universe unless the possible existence of such inhomogeneities is properly taken into account. Keywords->
ISSN:1475-7516
1475-7516
DOI:10.1088/1475-7516/2010/07/012