Primordial tensor bispectra in $μ$-CMB cross-correlations

Abstract

Cross-correlations between Cosmic Microwave Background (CMB) temperature and polarization anisotropies and µ-spectral distortions have been considered to measure (squeezed) primordial scalar bispectra in a range of scales inaccessible to primary CMB bispectra. In this work we address whether it is possible to constrain tensor non-Gaussianities with these cross-correlations. We find that only primordial tensor bispectra with anisotropies leave distinct signatures, while isotropic tensor bispectra leave either vanishing or highly suppressed signatures. We discuss how the kind of anisotropies and the parity state in primordial bispectra determine the non-zero cross-correlations. By employing the so-called BipoSH formalism to capture the observational effects of these anisotropies, we make Fisher-forecasts to assess the detection prospects from µT , µE and µB cross-correlations. Observing anisotropies in squeezed γγγ and γγζ bispectra is going to be challenging as the imprint of tensor perturbations on µ-distortions is subdominant to scalar perturbations, therefore requiring a large, independent amplification of the effect of tensor perturbations in the µ-epoch. In absence of such a mechanism, anisotropies in squeezed ζζγ bispectrum are the most relevant sources of µT , µE and µB cross-correlations. In particular, we point out that in models where anisotropies in ζζζ leave potentially observable signatures in µT and µE, the detection prospects of anisotropies in ζζγ from µB are enhanced.

Consistency conditions and primordial black holes in single field inflation

“…As first proposed in [21] (and further explored in [64][65][66][67][68][69][70]) non-Gaussianity at µ-distortion scales have distinctive consequences for µT correlators 5 among CMB µ-distortions and temperature fluctuations -sensitive to the squeezed limit of the bispectrum -and for µµ self correlations -sensitive to the collapsed limit of the trispectrum. In this section we go beyond work in [20] by developing the following points…”

“…See also[57] and[56] for an investigation on the Maldacena's consistency condition in slow-roll violating inflationary scenarios 5. See also[70,71] for the influence of primordial non-Gaussianities on µE and µB[69] cross correlations.…”

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

“…The first Ota (2016); Chluba et al (2017); Ravenni et al (2017). Recently it has been shown how the same idea can be applied to models involving primordial black holes (Özsoy & Tasinato 2021) and to models in which scalar and tensor perturbations are correlated (Orlando et al 2021). While fainter than the monopole signal, spectral distortions anisotropies do not require (Ganc & Komatsu 2012) the use of a purposefully-built absolutely-calibrated spectrometer (Chluba et al 2019), but can be extracted from differential measurement carried out by an imager (e.g.…”