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Journal of Cosmology and Astroparticle Physics 04 (2009) 021
Multi-field DBI inflation: introducing bulk forms and revisiting the gravitational wave constraints
D. Langlois1, 2, S. Renaux-Petel1, D.A. Steer1

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.
1 :  APC - UMR 7164 - AstroParticule et Cosmologie
2 :  IAP - Institut d'Astrophysique de Paris
Physique/Physique des Hautes Energies - Théorie

Physique/Astrophysique/Cosmologie et astrophysique extra-galactique

Planète et Univers/Astrophysique/Cosmologie et astrophysique extra-galactique

Physique/Relativité Générale et Cosmologie Quantique
inflation – string theory and cosmology
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