University of Portsmouth

About: University of Portsmouth is a education organization based out in Portsmouth, Portsmouth, United Kingdom. It is known for research contribution in the topics: Population & Galaxy. The organization has 5452 authors who have published 14256 publications receiving 424346 citations. The organization is also known as: Portsmouth and Gosport School of Science and Art & Portsmouth and Gosport School of Science and the Arts.

Primordial non-Gaussianity from the DBI Galileons

Abstract: We study primordial fluctuations generated during inflation in a class of models motivated by the DBI Galileons, which are extensions of the DBI action that yield second-order field equations. This class of models generalizes the DBI Galileons in a similar way with $K$ inflation. We calculate the primordial non-Gaussianity from the bispectrum of the curvature perturbations at leading order in the slow-varying approximations. We show that the estimator for the equilateral-type non-Gaussianity, ${f}_{\mathrm{NL}}^{\mathrm{equil}}$, can be applied to measure the amplitude of the primordial bispectrum even in the presence of the Galileon-like term although it gives a slightly different momentum dependence from $K$-inflation models. For the DBI Galileons, we find $\ensuremath{-}0.32/{c}_{s}^{2}l{f}_{\mathrm{NL}}^{\mathrm{equil}}l\ensuremath{-}0.16/{c}_{s}^{2}$ and large primordial non-Gaussianities can be obtained when ${c}_{s}$ is much smaller than 1 as in the usual DBI inflation. In $G$-inflation models, where a de Sitter solution is obtained without any potentials, the nonlinear parameter is given by ${f}_{\mathrm{NL}}^{\mathrm{equil}}=4.62{r}^{\ensuremath{-}2/3}$, where $r$ is the tensor to scalar ratio, giving a stringent constraint on the model.