Non-Gaussianity from the bispectrum in general multiple field inflation

By F. Arroja, S. Mizuno, K. Koyama. 2008

145 citations recorded by the source corpus.

We study the non-Gaussianity from the bispectrum in multi-field inflation models with a general kinetic term. The models include multi-field K-inflation and multi-field Dirac–Born–Infeld (DBI) inflation as special cases. We find that, in general, the sound speeds for the adiabatic and entropy perturbations are different and they can be smaller than 1. Then the non-Gaussianity can be enhanced. Multi-field DBI inflation is shown to be a special case where both sound speeds are the same due to a special form of the kinetic term (Langlois et al 2008 Preprint 0804.3139 [hep-th]). We derive the exact second-and third-order actions including metric perturbations. In the small sound speed limit and at leading order in the slow-roll expansion, we derive the three-point function for the curvature perturbation which depends on both adiabatic and entropy perturbations. The contribution from the entropy perturbations has a different momentum dependence if the sound speeds for the entropy and adiabatic perturbations are different, which provides a possibility to distinguish multi-field models from single-field models. On the other hand, in the multi-field DBI case, the contribution from the entropy perturbations has the same momentum dependence as the pure adiabatic contributions and it only changes the amplitude of the three-point function (Langlois et al 2008 Preprint 0804.3139 [hep-th]). This could help to ease the constraints on the DBI-inflation models.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/14d7b956123a9adac716c94d7568a95280ce181d

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Nuclear and High Energy Physics

Citations in the corpus

Non-Gaussianities in single field inflation and their optimal limits from the WMAP 5-year data (2009, background): “This is the shape that is produced in some proposed single-field or multi-field inflationary models, such as DBI inflation [15, 16, 17], or Ghost inflation [18, 19], where the inflaton has large derivative interactions, or Trapped inflation [21], where production of massive particles slows down the ”
Primordial Non-Gaussianities from Inflation Models (2010, background): “[96–102], where this type of kinetic terms are generalized to multiple fields.”
Review of local non-Gaussianity from multi-field inflation (2010, methodology): “There are several different fNL’s used in the literature which parameterise different shape dependences of the bispectrum [41, 42], the most popular being the local model discussed in this paper and the so-called equilateral model which can arise from models of inflation with noncanonical kinetic te”
The DESI Experiment Part I: Science,Targeting, and Survey Design (2016, background): “There are also hybrids of multi-field and non-slow-roll models [142, 143, 144], and the inclusion of isocurvature modes in the non-Gaussian correlations [145, 146, 147].”