Primordial perturbations and non-Gaussianities in DBI and general multifield inflation

By D. Langlois, S. Renaux-Petel, D. Steer, Takahiro Tanaka. 2008

286 citations recorded by the source corpus.

We study cosmological perturbations in general inflation models with multiple scalar fields and arbitrary kinetic terms, with special emphasis on the multifield extension of Dirac-Born-Infeld (DBI) inflation. We compute the second-order action governing the dynamics of linear perturbations in the most general case. Specializing to DBI inflation, we show that the adiabatic and entropy modes propagate with a common effective sound speed and are thus amplified at sound horizon crossing. In the small sound speed limit, we find that the amplitude of the entropy modes is much higher than that of the adiabatic modes. We also derive, in the general case, the third-order action which is useful for studying primordial non-Gaussianities generated during inflation. In the DBI case, we compute the dominant contributions to non-Gaussianities, which depend on both the adiabatic and entropy modes.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/e330f657463ad8db4faecaad9a67f4a3b5f35370

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

1. L. Senatore
2. M. Zaldarriaga
3. D. Baumann
4. D. Green
5. Xingang Chen
6. M. Liguori
7. J. Fergusson
8. L. Verde

In Nuclear and High Energy Physics

1. L. Senatore
2. M. Zaldarriaga
3. D. Green
4. D. Baumann
5. Xingang Chen
6. J. Fergusson
7. B. Horn
8. E. Silverstein

Citations in the corpus

• Planck 2015 results. XVII. Constraints on primordial non-Gaussianity (2015, unknown): “…bispectra because of the cross-correlation between isocurvature and adiabatic perturbations (Komatsu 2002; Bartolo et al. 2002; Komatsu et al. 2005; Kawasaki et al. 2008, 2009; Langlois et al. 2008; Hikage et al. 2009; Langlois & Lepidi 2011; Langlois & van Tent 2011, 2012; Kawakami et al. 2012).”
• COrE (Cosmic Origins Explorer) A White Paper (2011, background): “A linear combination of these shapes can also be realized [91].”
• The effective field theory of multifield inflation (2010, background): “For example in [37, 38] the possibility of these”
• Trapped Inflation (2009, background): “[34] for an analysis of possible shapes of the non-Gaussianity arising from multifield models with nontrivial kinetic terms.”