Showing papers by "Philippe Brax published in 2010"
TL;DR: In this article, the effect of trapped branes on the evolution of a test brane whose motion generates DBI inflation along a warped throat was considered, and it was shown that a single trapped brane can hardly slow down a DBI inflaton whose fluctuations lead to the Cosmic Microwave Background spectrum.
Abstract: We consider the effect of trapped branes on the evolution of a test brane whose motion generates DBI inflation along a warped throat. The coupling between the inflationary brane and a trapped brane leads to the radiation of non-thermal particles on the trapped brane. We calculate the Gaussian spectrum of the radiated particles and their backreaction on the DBI motion of the inflationary brane. Radiation occurs either due to a parametric resonance when the interaction time is small compared to the Hubble time or a tachyonic resonance when the interaction time is large. In both cases the motion of the inflationary brane after the interaction is governed by a chameleonic potential, which tends to slow it down. We find that a single trapped brane can hardly slow down a DBI inflaton whose fluctuations lead to the Cosmic Microwave Background spectrum. A more drastic effect is obtained when the DBI brane encounters a tightly spaced stack of trapped branes.
22 citations
TL;DR: In this article, the growth of cosmological perturbations in modified gravity models where a scalar field mediates a non-universal Yukawa force between different matter species is considered.
Abstract: We consider the growth of cosmological perturbations in modified gravity models where a scalar field mediates a non-universal Yukawa force between different matter species. The growth of the density contrast is altered for scales below the Compton wave-length of the scalar field. As the universe expands, the Compton wave-length varies in time in such a way that scales which were outside the range of the scalar field force may feel it at a lower redshift. In this case, both the exponent γ measuring the growth of Cold Dark Matter perturbations and the slip function representing the ratio of the two Newtonian potentials ψ and may differ from their values in General Relativity at low redshift.
13 citations