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Primordial fluctuations and non-Gaussianities in multifield Dirac-Born-Infeld inflation
David Langlois1, Sébastien Renaux-Petel, Danièle A Steer
1APC, UMR 7164, 10 rue Alice Domon et Léonie Duquet,75205 Paris Cedex 13, France.
Physical Review Letters
|September 4, 2008
Summary
Multi-field Dirac-Born-Infeld inflation models show amplified entropy modes. In the small sound speed limit, entropy modes dominate, impacting the curvature power spectrum and non-Gaussianities.
Area of Science:
- Cosmology
- Theoretical Physics
- Particle Physics
Background:
- The standard cosmological model relies on cosmic inflation.
- Dirac-Born-Infeld (DBI) models offer an alternative framework for inflation.
- Multi-field extensions of DBI inflation are theoretically motivated but complex.
Purpose of the Study:
- To investigate the behavior of multi-field Dirac-Born-Infeld inflation models.
- To analyze the propagation and amplification of adiabatic and entropy modes.
- To determine the impact of these modes on observable cosmological quantities.
Main Methods:
- Analytical study of multi-field Dirac-Born-Infeld Lagrangian.
- Analysis of mode propagation and sound speed.
- Investigation of the small sound speed limit.
Main Results:
- Adiabatic and entropy modes share a common effective sound speed.
- In the small sound speed limit, entropy modes are significantly amplified compared to adiabatic modes.
- The observable curvature power spectrum and non-Gaussianities are strongly affected.
Conclusions:
- Multi-field DBI inflation exhibits distinct features compared to single-field models.
- The amplification of entropy modes has significant observational consequences.
- The shape of non-Gaussianities remains similar to the single-field DBI case.
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