Mixing of blackbodies: Increasing our view of inflation to 17 e-folds with spectral distortions from Silk damping

TL;DR

This paper discusses how spectral distortions in the CMB caused by Silk damping can extend our observational window of inflation to 17 e-folds by revealing primordial power spectrum information on small scales.

Contribution

It introduces a method to use CMB spectral distortions from Silk damping to probe inflationary scales beyond current anisotropy measurements.

Findings

Spectral distortions encode primordial power on small scales.

Combining distortions with anisotropies extends inflationary insights to 17 e-folds.

Silk damping effects can be modeled as mixing of blackbodies.

Abstract

Silk damping in the early Universe, before and during recombination, erases anisotropies in the cosmic microwave background (CMB) on small scales. This power, which disappears from anisotropies, appears in the monopole as y-type, i-type and \mu-type distortions. The observation of the CMB spectral distortions will thus make available to us the information about the primordial power spectrum on scales corresponding to the comoving wavenumbers $8< k < 10^4 Mpc^{-1}$ increasing our total view of inflation, when combined with CMB anisotropies, to span 17 e-folds. These distortions can be understood simply as mixing of blackbodies of different temperatures and the subsequent comptonization of the resulting distortions.