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The Non-Minimal Ekpyrotic Trispectrum

Fertig, A., & Lehners, J.-L. (2016). The Non-Minimal Ekpyrotic Trispectrum. Journal of Cosmology and Astroparticle Physics, 2016(01): 26. doi:10.1088/1475-7516/2016/01/026.

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Fertig, Angelika1, Author
Lehners, Jean-Luc2, Author
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1Theoretical Cosmology, AEI-Golm, MPI for Gravitational Physics, Max Planck Society, ou_1753351
2String Cosmology, AEI-Golm, MPI for Gravitational Physics, Max Planck Society, ou_1753351

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Free keywords: High Energy Physics - Theory, hep-th,Astrophysics, Cosmology and Extragalactic Astrophysics, astro-ph.CO
Abstract: Employing the covariant formalism, we derive the evolution equations for two scalar fields with non-canonical field space metric up to third order in perturbation theory. These equations can be used to derive predictions for local bi- and trispectra of multi-field cosmological models. Our main application is to ekpyrotic models in which the primordial curvature perturbations are generated via the non-minimal entropic mechanism. In these models, nearly scale-invariant entropy perturbations are generated first due to a non-minimal kinetic coupling between two scalar fields, and subsequently these perturbations are converted into curvature perturbations. Remarkably, the entropy perturbations have vanishing bi- and trispectra during the ekpyrotic phase. However, as we show, the conversion process to curvature perturbations induces local non-Gaussianity parameters $f_{NL}$ and $g_{NL}$ at levels that should be detectable by near-future observations. In fact, in order to obtain a large enough amplitude and small enough bispectrum of the curvature perturbations, as seen in current measurements, the conversion process must be very efficient. Interestingly, for such efficient conversions the trispectrum parameter $g_{NL}$ remains negative and typically of a magnitude ${\cal O}(10^2) - {\cal O}(10^3),$ resulting in a distinguishing feature of non-minimally coupled ekpyrotic models.

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Dates: 2015-10-122016
Publication Status: Published in print
Pages: 47 pages, 7 figures
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Identifiers: arXiv: 1510.03439
URI: http://arxiv.org/abs/1510.03439
DOI: 10.1088/1475-7516/2016/01/026
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Title: Journal of Cosmology and Astroparticle Physics
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Pages: - Volume / Issue: 2016 (01) Sequence Number: 26 Start / End Page: - Identifier: -