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Non-Gaussianity in multi-sound-speed disformally coupled inflation
Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
Number of Authors: 3
2017 (English)In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 2, 1-29 p., 029Article in journal (Refereed) Published
Abstract [en]

Most, if not all, scalar-tensor theories are equivalent to General Relativity with a disformally coupled matter sector. In extra-dimensional theories such a coupling can be understood as a result of induction of the metric on a brane that matter is confined to. This article presents a first look at the non-Gaussianities in disformally coupled inflation, a simple two-field model that features a novel kinetic interaction. Cases with both canonical and Dirac-Born-Infeld (DBI) kinetic terms are taken into account, the latter motivated by the possible extra-dimensional origin of the disformality. The computations are carried out for the equilateral con figuration in the slow-roll regime, wherein it is found that the non-Gaussianity is typically rather small and negative. This is despite the fact that the new kinetic interaction causes the perturbation modes to propagate with different sounds speeds, which may both significantly deviate from unity during inflation.

Place, publisher, year, edition, pages
2017. no 2, 1-29 p., 029
Keyword [en]
inflation, non-gaussianity, modified gravity, string theory and cosmology
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:su:diva-143487DOI: 10.1088/1475-7516/2017/02/029ISI: 000399455000029OAI: oai:DiVA.org:su-143487DiVA: diva2:1103926
Available from: 2017-05-31 Created: 2017-05-31 Last updated: 2017-05-31Bibliographically approved

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Koivisto, Tomi
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