http://arxiv.org/abs/1808.10517
Early energy injection to the Cosmic Microwave Background (CMB) from dissipation of acoustic waves generates deviations from the blackbody spectrum not only at second-order but also at third-order in cosmological perturbations. For the first time, we compute this new spectral distortion $\mathcal \kappa$ based on third-order cosmological perturbation theory. We point out that $\kappa$ arises from heat conduction and shear viscosity of spectral distortions and temperature perturbations. The ensemble average of $\kappa$ can be directly sourced by primordial non-Gaussianity, being an integral of the primordial bispectrum and thus depending on its shape. For local non-Gaussianity we roughly estimate the signal and find $\kappa=f^{\rm loc.}_{\rm NL}\times \mathcal O(10^{-18})$. The signal is incredibly tiny; however, we argue that it carries a specific frequency dependence different from other types of CMB spectral distortions. Moreover, we comment on other possible applications of our results.
A. Ota and N. Bartolo
Mon, 3 Sep 18
23/54
Comments: 6 pages, 3 figures