Sixteenth Marcel Grossmann Meeting

Cross-correlation between CMB polarization and mu-distortion anisotropies as a path towards the detection of small-scale primordial non-Gaussianity

6 Jul 2021, 12:12

18m

Invited talk in the parallel session New Horizons in Cosmology with CMB Spectral Distortions New Horizons in Cosmology with CMB Spectral Distortions

Speaker

Mathieu Remazeilles

Description

The dissipation of primordial perturbation modes with wavenumbers $50{\mathrm{M}\mathrm{p}\mathrm{c}}^{-1}<k<{10}^4{\mathrm{M}\mathrm{p}\mathrm{c}}^{-1}$ in the early Universe cause $\mu$-type spectral distortions to the average CMB blackbody radiation. Besides, some inflation scenarios (multi-field or single-field inflation with modified initial state) predict large primordial non-Gaussianity at these scales, so that non-Gaussian couplings between short and long-wavelength modes can modulate the damping of small-scale perturbations across different directions in the sky, and thus induce anisotropic $\mu$-distortions which are furthermore correlated with CMB temperature and polarization anisotropies.

Through signal enhancement by cross-correlation with CMB anisotropies, the $\mu$-distortion anisotropies could potentially be detected by future CMB imagers like the LiteBIRD satellite, and would allow to constrain $f_{\mathrm{N}\mathrm{L}}$ at the very small scales $50{\mathrm{M}\mathrm{p}\mathrm{c}}^{-1}<k<{10}^4{\mathrm{M}\mathrm{p}\mathrm{c}}^{-1}$ which are inaccessible to both CMB anisotropies and LSS surveys.

In this talk we will present our forecasts on the recovery of the cross-power spectra $C_{\ell }^{\mu T}$ and $C_{\ell }^{\mu E}$ between $\mu$-distortion anisotropies and CMB temperature and $E$-mode polarization anisotropies in the presence of astrophysical foregrounds for a LiteBIRD-type experiment. In particular, we will show how $\mu$-$E$ correlations (i.e. $C_{\ell }^{\mu E}$) actually provide more constraining power on $f_{\mathrm{N}\mathrm{L}}$ than $\mu$-$T$ correlations in the presence of foregrounds, and how the sensitivity to $f_{\mathrm{N}\mathrm{L}}$ at small scales can be further increased by the joint analysis of $\mu$-$T$ and $\mu$-$E$ correlations.