Effects of the speed of sound at large-N

Abstract

The implications of a smaller than unity speed of sound of the scalar perturbations during cosmic inflation is studied in terms of a model independent large-$N$ approach. We show that the $(n_s,r)$ plane is non-trivially degenerated when the effects of a different than one speed of sound $c_s$ are taken into account. We also discuss the degeneracies due to $c_s$ in the running of the spectral index, ${\alpha }_s$. We use the bounds on $c_s$ to constrain such degeneracies.

arXiv comment4 figures, 5 pages. References added. Typos corrected. Improved discussion. Version to appear in PRD

References in corpus (23)

• k-Inflation
• BICEP2 I: Detection Of B-mode Polarization at Degree Angular Scales
• Perturbations in k-inflation
• The Effective Field Theory of Inflation
• Planck 2013 results. XXII. Constraints on inflation
• DBI in the Sky
• Encyclopaedia Inflationaris
• What would we learn by detecting a gravitational wave signal in the cosmic microwave background anisotropy?
• Scalar Speed Limits and Cosmology: Acceleration from D-cceleration
• Effective Field Theory for Inflation
• Planck 2013 Results. XXIV. Constraints on primordial non-Gaussianity
• Running Non-Gaussianities in DBI Inflation
• A Microscopic Limit on Gravitational Waves from D-brane Inflation
• Quantum Cosmological Perturbations: Predictions and Observations
• Universality classes of inflation
• Scale dependence of local f_NL
• The large-N running of the spectral index of inflation
• B-modes and the Nature of Inflation
• The Lyth Bound of Inflation with a Tilt
• Cosmological constraints on general, single field inflation
• Can CMB data constrain the inflationary field range?
• A model-independent fit to Planck and BICEP2 data
• Warped Wilson Line DBI Inflation

Cited by in corpus (6)

• Mechanisms for Primordial Black Hole Production in String Theory
• Cosmological Attractors from $\alpha$-Scale Supergravity
• On the viability of m**2 phi**2 and natural inflation
• Planck Limits on Non-canonical Generalizations of Large-field Inflation Models
• On the Three Primordial Numbers
• B-modes and the sound speed of primordial fluctuations