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G. J. Mathews, P. M. Garnavich (University of Notre Dame), K. Ichiki, T. Kajino (NAO Japan), M. Yahiro (University of Ryukyus)
There is currently considerable interest in the possibility that our universe could be a submanifold embedded in a higher-dimensional spacetime. This brane-world paradigm is motivated by the D-brane solution found in ten-dimensional superstring theory. Here, we describe constraints from big-bang nucleosynthesis, high redshift supernovae, and the galaxy cluster mass-to-light ratios on the existence of such extra dimensions. In particular, we analyze the constraints on the currently popular Randall-Sundrum brane-world cosmology whereby the universe is described as a three-brane embedded in a five-dimensional anti-de Sitter space with a large (infinite) extra dimension. In this cosmology, the usual Friedmann equation contains extra terms which derive from existence of the extra dimension. We concentrate on the ``dark radiation'' term and show that, although only a small positive contribution is allowed, a much wider range of negative values is possible. Such a negative contribution can reconcile the tension between the observed primordial 4He and D abundances. Another consequence of a large extra dimension is that massive particles can be metastable and literally disappear into the bulk dimension. Here, we examine the new possibility that dark matter decays into the extra dimension. We show that disappearing dark matter is consistent (at the 95% confidence level) with both present observations of Type Ia supernovae at the highest redshift and trends in the mass-to-light ratios of galactic clusters with redshift.
Work supported in part by the U.S. Department of Energy under Grant DE-FG02-95-ER40934 and NASA grant NAG5-9364.
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The author(s) of this abstract have provided an email address for comments about the abstract: gmathews@nd.edu
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.