Observational constraints on dark radiation in brane cosmology

Center for Astrophysics, Department of Physics,University of Notre Dame, Notre Dame, IN 46556(Dated: February 5, 2008)We analyze the observational constraints on brane-world cosmology whereby the universe is de-scribed as a three-brane embedded in a five-dimensional anti-de Sitter space. In this brane-universecosmology, the Friedmann equation is modified by the appearance of extra terms which derive fromexistence of the extra dimensions. In the present work we concentrate on the “dark radiation”term which diminishes with cosmic scale factor as a