Observational constraints on dark radiation in brane cosmology

K. Ichiki, M. Yahiro, T. Kajino, M. Orito, G. J. Mathews

Research output: Contribution to journalArticlepeer-review

115 Citations (Scopus)


We analyze the observational constraints on brane-world cosmology whereby the universe is described as a three-brane embedded in a five-dimensional anti-de Sitter space. In this brane-universe cosmology, the Friedmann equation is modified by the appearance of extra terms which derive from the existence of the extra dimensions. In the present work we concentrate on the "dark radiation" term which diminishes with the cosmic scale factor as a -4. We show that, although the observational constraints from primordial abundances allow only a small contribution when this term is positive, a much wider range of negative values is allowed. Furthermore, such a negative contribution can reconcile the tension between the observed primordial 4He and D abundances. We also discuss the possible constraints on this term from the power spectrum of CMB anisotropies in the limit of negligible cosmological perturbation on the brane world. We show that BBN limits the possible contribution from dark radiation just before the e+e - annihilation epoch to lie between -123% and +11% of the background photon energy density. Combining this with the CMB constraint reduces this range to between -41% and +10.5% at the 2 σ confidence level.

Original languageEnglish
Article number043521
JournalPhysical Review D
Issue number4
Publication statusPublished - 2002
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)


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