Primordial fluctuations and non-Gaussianities from multifield DBI Galileon inflation

Journal Article · Tue Nov 01 04:00:00 EDT 2011 · Journal of Cosmology and Astroparticle Physics

DOI:https://doi.org/10.1088/1475-7516/2011/11/042· OSTI ID:22279706

Renaux-Petel, Sébastien ^[1]; Mizuno, Shuntaro; Koyama, Kazuya ^[2]

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1. Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge (United Kingdom)
2. Institute of Cosmology and Gravitation, University of Portsmouth, Burnaby Road, Portsmouth (United Kingdom)

We study a cosmological scenario in which the DBI action governing the motion of a D3-brane in a higher-dimensional spacetime is supplemented with an induced gravity term. The latter reduces to the quartic Galileon Lagrangian when the motion of the brane is non-relativistic and we show that it tends to violate the null energy condition and to render cosmological fluctuations ghosts. There nonetheless exists an interesting parameter space in which a stable phase of quasi-exponential expansion can be achieved while the induced gravity leaves non trivial imprints. We derive the exact second-order action governing the dynamics of linear perturbations and we show that it can be simply understood through a bimetric perspective. In the relativistic regime, we also calculate the dominant contribution to the primordial bispectrum and demonstrate that large non-Gaussianities of orthogonal shape can be generated, for the first time in a concrete model. More generally, we find that the sign and the shape of the bispectrum offer powerful diagnostics of the precise strength of the induced gravity.

• OSTI ID: 22279706
• Journal Information: Journal of Cosmology and Astroparticle Physics, Journal Name: Journal of Cosmology and Astroparticle Physics Journal Issue: 11 Vol. 2011; ISSN 1475-7516
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
BORN-INFELD THEORY
DISTURBANCES
FLUCTUATIONS
GRAVITATION
INFLATIONARY UNIVERSE
INFLATONS
LAGRANGIAN FUNCTION
RELATIVISTIC RANGE
SPACE-TIME