Orateur
Description
Multi-field inflation models predict sizeable non-Gaussian primordial perturbations and consequently anisotropic $\mu$-type spectral distortions of the cosmic microwave background (CMB) blackbody. While CMB anisotropies allow us to probe primordial non-Gaussianity at wavenumbers $k \simeq 0.05\,{\rm Mpc}^{−1}$, $\mu$-distortion anisotropies are related to non-Gaussianity of primordial perturbation modes with much larger wavenumbers, $k ≃ 740\, {\rm Mpc}^{-1}$. Through cross-correlations between CMB anisotropies and $\mu$-distortion anisotropies, one can therefore shed light on the aforementioned inflation models. We will discuss the capabilities of a future CMB satellite imager like LiteBIRD to measure $\mu T$ and $\mu E$ cross-power spectra between anisotropic $\mu$-distortions and CMB temperature and E-mode polarization anisotropies in the presence of foregrounds, and present LiteBIRD forecasts on $f_{\rm NL}^\mu(k \simeq 740\, {\rm Mpc}^{−1})$. We will show that $\mu E$ cross-correlations with CMB polarization actually provide more constraining power on $f_{\rm NL}^\mu$ than $\mu T$ cross-correlations in the presence of foregrounds, and that the joint combination of $\mu T$ and $\mu E$ observables adds further leverage to the detection of small-scale primordial non-Gaussianity with future CMB imagers.
