Cherenkov in the Sky: Measuring the Sound Speed of Primordial Scalar Fluctuations

Abstract

We consider production of additional relativistic particles coupled to the inflaton. We show that the imprints of these particles on the spectrum of primordial perturbations can be used for the direct measurement of the speed of sound of scalar perturbations, regardless of the mechanism of the production of this species. We study a model where these relativistic localized sources are decay products of heavier particles generated via a resonance mechanism. These particles emit in-phase inflaton particles which interfere constructively on the the so-called sound boom, leading to an "inflationary Cherenkov effect". The resulting shock waves lead to distinctive patterns on the temperature anisotropies of the cosmic microwave background. Moreover, we show that the model predicts unique features on the power spectrum of curvature perturbation and sizeable flattened non-gaussianity for a suitable range of parameters.

18 pages, 3 figures

References in corpus (10)

• The Effective Field Theory of Inflation
• A Joint Analysis of BICEP2/Keck Array and Planck Data
• On the consistency relation of the 3-point function in single field inflation
• Blue Tensor Spectrum from Particle Production during Inflation
• Effects of particle production during inflation
• Large non-Gaussianities in the Effective Field Theory Approach to Single-Field Inflation: the Trispectrum
• A Naturally Large Four-Point Function in Single Field Inflation
• On Features and Nongaussianity from Inflationary Particle Production
• Gravitational Waves and the Scale of Inflation
• Stochastic Particle Production in a de Sitter Background