Lorentz boost and non-gaussianity in multi-field dbi-inflation

Shuntaro Mizuno, Frederico Arroja, Kazuya Koyama, Takahiro Tanaka

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

We show that higher-order actions for cosmological perturbations in the multi-field DBI inflation model are obtained by a Lorentz boost from the rest frame of the brane to the frame where the brane is moving. We confirm that this simple method provides the same third- And fourth- order actions at leading order in slow-roll and in the small sound speed limit as those obtained by the usual ADM formalism. As an application, we compute the leading order connected four-point function of the primordial curvature perturbation coming from the intrinsic fourth-order contact interaction in the multi-field DBI-inflation model. At third order, the interaction Hamiltonian arises purely by the boost from the second-order action in the rest frame of the brane. The boost acts on the adiabatic and entropy modes in the same way thus there exists a symmetry between the adiabatic and entropy modes. But at fourth order this symmetry is broken due to the intrinsic fourth-order action in the rest frame and the difference between the Lagrangian and the interaction Hamiltonian. Therefore, contrary to the three-point function, the momentum dependence of the purely adiabatic component and the components including the entropic contributions are different in the four-point function. This suggests that the trispectrum can distinguish the multi-field DBI-inflation model from the single field DBI inflation model.

Original languageEnglish
Title of host publication12th Marcel Grossmann Meeting on Recent Dev. in Theoretical and Experimental General Relativity, Astrophysics and Relativistic Field Theories - Proc. of the MG 2009 Meeting on General Relativity
Pages1231-1233
Number of pages3
Publication statusPublished - 2012
Externally publishedYes
Event12th Marcel Grossmann Meeting on Recent Developments in Theoretical and Experimental General Relativity, Astrophysics and Relativistic Field Theories, MG 2009 - Paris
Duration: 2009 Jul 122009 Jul 18

Other

Other12th Marcel Grossmann Meeting on Recent Developments in Theoretical and Experimental General Relativity, Astrophysics and Relativistic Field Theories, MG 2009
CityParis
Period09/7/1209/7/18

Keywords

  • Inflation;String theory;Cosmology

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Nuclear and High Energy Physics

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