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Observational constraints on phantom-like braneworld cosmologies

Ruth Lazkoz, Roy Maartens, Elisabetta Majerotto

astro-pharXiv:astro-ph/0605701

Abstract

We investigate a simple braneworld model in which the universe contains only cold dark matter and a cosmological constant, but the effective dark energy is phantom-like because of extra-dimensional gravity effects. Modified gravity screens the cosmological constant Lambda, allowing for a larger Lambda. In practice, observations do not favour any significant screening. We use supernova data, the cosmic microwave background shift parameter, and the baryon oscillation peak in the galaxy distribution to constrain the model. We find the mean value of Omegam with 68% confidence limits, and an upper limit on OmegaLambda at the 68% confidence level. The best-fit model is very close to a standard LCDM model, but the LCDM model provides a better fit since it has one less parameter.

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