WMAP constraints on scalar-tensor cosmology and the variation of the gravitational constant

Ryo Nagata, Takeshi Chiba, and Naoshi Sugiyama
Phys. Rev. D 69, 083512 – Published 14 April 2004
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Abstract

We present observational constraints on a scalar-tensor gravity theory by χ2 test for the CMB anisotropy spectrum. We compare the WMAP temperature power spectrum with the harmonic attractor model, in which the scalar field has its harmonic effective potential with a curvature β in the Einstein conformal frame and the theory relaxes toward Einstein gravity with time. We find that the present value of the scalar coupling, i.e., the present level of deviation from Einstein gravity (α02), is bounded to be smaller than 5×1047β(2σ), and 1027β(4σ) for 0<β<0.45. This constraint is much stronger than the bound from the solar system experiments for large β models, i.e., β>0.2 and 0.3 in 2σ and 4σ limits, respectively. Furthermore, within the framework of this model, the variation of the gravitational constant at the recombination epoch is constrained as |G(z=zrec)G0|/G0<0.05(2σ), and 0.23(4σ).

  • Received 12 November 2003

DOI:https://doi.org/10.1103/PhysRevD.69.083512

©2004 American Physical Society

Authors & Affiliations

Ryo Nagata*

  • Division of Theoretical Astrophysics, National Astronomical Observatory, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan
  • Department of Physics, Kyoto University, Kyoto 606-8502, Japan

Takeshi Chiba

  • Department of Physics, Kyoto University, Kyoto 606-8502, Japan

Naoshi Sugiyama

  • Division of Theoretical Astrophysics, National Astronomical Observatory, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan

  • *Electronic address: nagata@th.nao.ac.jp

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Vol. 69, Iss. 8 — 15 April 2004

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