Primordial non-Gaussianity from the DBI Galileons
- Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX (United Kingdom)
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{sub NL}{sup 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 -0.32/c{sub s}{sup 2}<f{sub NL}{sup equil}<-0.16/c{sub s}{sup 2} and large primordial non-Gaussianities can be obtained when c{sub 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{sub NL}{sup equil}=4.62r{sup -2/3}, where r is the tensor to scalar ratio, giving a stringent constraint on the model.
- OSTI ID:
- 21503606
- Journal Information:
- Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 10 Vol. 82; ISSN PRVDAQ; ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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