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

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 c...

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Published inJournal of cosmology and astroparticle physics Vol. 2009; no. 4; p. 021
Main Authors Langlois, David, Renaux-Petel, Sébastien, Steer, Danièle A
Format Journal Article
LanguageEnglish
Published United States IOP Publishing 22.04.2009
Institute of Physics (IOP)
Subjects
Astrophysics
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BORN-INFELD THEORY
COMPACTIFICATION
Cosmology and Extra-Galactic Astrophysics
D-BRANES
DIRAC COSMOLOGY
DISTURBANCES
ENTROPY
FLUCTUATIONS
GAUGE INVARIANCE
General Relativity and Quantum Cosmology
GRAVITATIONAL WAVES
High Energy Physics - Theory
INFLATIONARY UNIVERSE
LIMITING VALUES
NONLUMINOUS MATTER
Physics
PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
SCALARS
Sciences of the Universe
U-1 GROUPS
inflation
string theory and cosmology
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Summary: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.
ISSN:1475-7516
1475-7508
1475-7516
DOI:10.1088/1475-7516/2009/04/021