Quantum fluctuations in the Dvali-Gabadadze-Porrati model and the size of the crossover scale

O. Pujolàs

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Resum

The Dvali–Gabadadze–Porrati model introduces a parameter, the crossover scale rc, setting the scale where higher dimensional effects are important. In order to agree with observations and to explain the current acceleration of the Universe, rc must be of the order of the present Hubble radius. We discuss a mechanism for generating a large rc, assuming that it is determined by a dynamical field and exploiting the quantum effects of the graviton. For simplicity, we consider a scalar field Ψ with a kinetic term on the brane instead of the full metric perturbations. We compute the Green function and the one-loop expectation value of the stress tensor of Ψ on the background defined by a flat bulk and an inflating brane (self-accelerated or not). We also include the flat brane limit. The quantum fluctuations of the bulk field Ψ provide an effective potential for rc. For a flat brane, the one-loop effective potential Veff(rc) is of the Coleman–Weinberg form, and admits a minimum for large rc without fine-tuning. When we take into account the brane curvature, a sizable contribution at the classical level changes this picture. In this case, the potential can develop a minimum (maximum) for the non-self-accelerated (self-accelerated) branch.
Idioma originalAnglès
Número d’article004
RevistaJournal of Cosmology and Astroparticle Physics
Volum10
DOIs
Estat de la publicacióPublicada - 2006

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