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Multi-field DBI inflation: introducing bulk forms and revisiting the gravitational wave constraints

David Langlois 1 S. Renaux-Petel 2 D.A. Steer 2
APC (UMR_7164) - AstroParticule et Cosmologie, Institut für theoretische Physik
Abstract : We study multi-field Dirac-Born-Infeld (DBI) inflation models, taking into account the NS-NS and R-R bulk fields present in generic flux compactifications. We compute the second-order action, which governs the behaviour of linear cosmological perturbations, as well as the third-order action, which can be used to calculate non-Gaussianities in these models. Remarkably, for scalar-type perturbations, we show that the contributions due to the various form fields exactly cancel in both the second- and third-order actions. Primordial perturbations and their non-Gaussianities are therefore unaffected by the presence of form fields and our previous results are unmodified. We also study vector-type perturbations associated with the U(1) gauge field confined on the D3-brane, and discuss whether their quantum fluctuations can be amplified. Finally, we revisit the gravitational wave constraints on DBI inflation and show that an ultra-violet DBI multi-field scenario is still compatible with data, in contrast with the single field case, provided there is a transfer from entropy into adiabatic perturbations.
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Submitted on : Monday, March 23, 2009 - 10:07:20 AM
Last modification on : Wednesday, October 21, 2020 - 4:32:15 PM

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David Langlois, S. Renaux-Petel, D.A. Steer. Multi-field DBI inflation: introducing bulk forms and revisiting the gravitational wave constraints. Journal of Cosmology and Astroparticle Physics, Institute of Physics (IOP), 2009, 04, pp.021. ⟨10.1088/1475-7516/2009/04/021⟩. ⟨in2p3-00369612⟩



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