Inflationary Trispectrum From Graviton Exchange

Journal of Cosmology and Astroparticle Physics, 2009

Journal of Cosmology and Astroparticle Physics, 2009

Journal of Cosmology and Astroparticle Physics, 2012

Physical Review D, 1991

Journal of Cosmology and Astroparticle Physics, 2013

Journal of Cosmology and Astroparticle …, 2005

Physical Review D, 2015

We compute the tree-level connected four-point function of the primordial curvature perturbation for a fairly general minimally coupled single field inflationary model, where the inflaton's Lagrangian is a general function of the scalar field and its first derivatives. This model includes K-inflation and DBI-inflation as particular cases. We show that, at the leading order in the slow-roll expansion and in the small sound speed limit, there are two important tree-level diagrams for the trispectrum. One is a diagram where a scalar mode is exchanged and the other is a diagram where the interaction occurs at a point, i.e. a contact interaction diagram. The scalar exchange contribution is comparable to the contact interaction contribution. For the DBI-inflation model, in the so-called equilateral configuration, the scalar exchange trispectrum is maximized when the angles between the four momentum vectors are equal and in this case the amplitude of the trispectrum from the scalar exchange is one order of magnitude higher than the contact interaction trispectrum.

Physics Letters B, 2006

Journal of Cosmology and Astroparticle Physics, 2010

We make an complementary investigation of the primordial trispectrum from exchanging intermediate scalar modes in multi-field inflation models with generalized kinetic terms. Together with the calculation of irreducible contributions to the primordial trispectrum in Ref.[103], we give the full leading-order primordial trispectrum in generalized multi-field models.