Journal
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
Volume -, Issue 10, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/1475-7516/2009/10/012
Keywords
inflation; string theory and cosmology; non-gaussianity
Funding
- Science and Technology Facilities Council [ST/F002998/1] Funding Source: researchfish
- STFC [ST/F002998/1] Funding Source: UKRI
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We study multifield aspects of Dirac-Born-Infeld (DBI) inflation. More specifically, we consider an inflationary phase driven by the radial motion of a D-brane in a conical throat and determine how the D-brane fluctuations in the angular directions can be converted into curvature perturbations when the tachyonic instability arises at the end of inflation. The simultaneous presence of multiple fields and non-standard kinetic terms gives both local and equilateral shapes for non-Gaussianities in the bispectrum. We also study the trispectrum, pointing out that it acquires a particular momentum dependent component whose amplitude is given by f(NL)(loc)f(NL)(eq). We show that this relation is valid in every multifield DBI model, in particular for any brane trajectory, and thus constitutes an interesting observational signature of such scenarios.
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