Leverage on small-scale primordial non-Gaussianity through cross-correlations between CMB E-mode and μ-distortion anisotropies

• Main Authors: Chluba, J. (Author), Ravenni, A. (Author), Remazeilles, M. (Author)
• Format: Article
• Language: English
• Published: Oxford University Press 2022
• Subjects: (cosmology:) cosmic background radiation; (cosmology:) early universe; (cosmology:) early Universe; (cosmology:) inflation; Anisotropy; Cosmic background radiation; Cosmic microwaves background; Cosmology; Cosmology: early Universe; Cross-correlations; methods: analytical; Methods:analytical; polarization; Polarization; Primordial Non-Gaussianity; Wave numbers
• Online Access: View Fulltext in Publisher

 Multifield inflation models and non-Bunch-Davies vacuum initial conditions both predict sizeable non-Gaussian primordial perturbations and anisotropic μ-type spectral distortions of the cosmic microwave background (CMB) blackbody. While CMB anisotropies allow us to probe non-Gaussianity at wavenumbers k≃ 0.051, μ-distortion anisotropies are related to non-Gaussianity of primordial perturbation modes with much larger wavenumbers, k≃ 740, Mpc-1. Through cross-correlations between CMB and μ-distortion anisotropies, one can therefore shed light on the aforementioned inflation models. We investigate the ability of a future CMB satellite imager like LiteBIRD to measure μT and μE cross-power spectra between anisotropic μ-distortions and CMB temperature and E-mode polarization anisotropies in the presence of foregrounds, and derive LiteBIRD forecasts on fNLμ (k≃ 740Mpc-1)}. We show that μE cross-correlations with CMB polarization provide more constraining power on fNLμ than μT cross-correlations in the presence of foregrounds, and the joint combination of μT and μE observables adds further leverage to the detection of small-scale primordial non-Gaussianity. For multifield inflation, we find that LiteBIRD would detect {fNLμ }=4500 at 5σ significance after foreground removal, and achieve a minimum error of {\sigma (fNLμ =0) ≃ 800} at 68 per cent CL by combining CMB temperature and polarization. Due to the huge dynamic range of wavenumbers between CMB and μ-distortion anisotropies, such large fμ NL values would still be consistent with current CMB constraints in the case of very mild scale dependence of primordial non-Gaussianity. Anisotropic spectral distortions thus provide a new path, complementary to CMB B-modes, to probe inflation with LiteBIRD. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.