Primordial non-Gaussianity from the DBI Galileons

Shuntaro Mizuno, Kazuya Koyama

Research output: Contribution to journalArticle

105 Citations (Scopus)

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, fNLequil, 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/cs2<fNLequil<-0. 16/cs2 and large primordial non-Gaussianities can be obtained when cs 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 fNLequil=4.62r⊃-2⊃/3, where r is the tensor to scalar ratio, giving a stringent constraint on the model.

Original languageEnglish
Article number103518
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Volume82
Issue number10
DOIs
Publication statusPublished - 2010 Nov 12
Externally publishedYes

Fingerprint

estimators
curvature
tensors
scalars
momentum
perturbation
approximation

ASJC Scopus subject areas

  • Nuclear and High Energy Physics

Cite this

Primordial non-Gaussianity from the DBI Galileons. / Mizuno, Shuntaro; Koyama, Kazuya.

In: Physical Review D - Particles, Fields, Gravitation and Cosmology, Vol. 82, No. 10, 103518, 12.11.2010.

Research output: Contribution to journalArticle

@article{9bd2f529cdd84778af84d87d35465b03,
title = "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, fNLequil, 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/cs2s 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 fNLequil=4.62r⊃-2⊃/3, where r is the tensor to scalar ratio, giving a stringent constraint on the model.",
author = "Shuntaro Mizuno and Kazuya Koyama",
year = "2010",
month = "11",
day = "12",
doi = "10.1103/PhysRevD.82.103518",
language = "English",
volume = "82",
journal = "Physical review D: Particles and fields",
issn = "0556-2821",
publisher = "American Institute of Physics Publising LLC",
number = "10",

}

TY - JOUR

T1 - Primordial non-Gaussianity from the DBI Galileons

AU - Mizuno, Shuntaro

AU - Koyama, Kazuya

PY - 2010/11/12

Y1 - 2010/11/12

N2 - 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, fNLequil, 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/cs2s 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 fNLequil=4.62r⊃-2⊃/3, where r is the tensor to scalar ratio, giving a stringent constraint on the model.

AB - 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, fNLequil, 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/cs2s 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 fNLequil=4.62r⊃-2⊃/3, where r is the tensor to scalar ratio, giving a stringent constraint on the model.

UR - http://www.scopus.com/inward/record.url?scp=78651260477&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=78651260477&partnerID=8YFLogxK

U2 - 10.1103/PhysRevD.82.103518

DO - 10.1103/PhysRevD.82.103518

M3 - Article

AN - SCOPUS:78651260477

VL - 82

JO - Physical review D: Particles and fields

JF - Physical review D: Particles and fields

SN - 0556-2821

IS - 10

M1 - 103518

ER -