Parity violation in the CMB bispectrum by a rolling pseudoscalar

TL;DR

This paper explores parity-violating signals in the CMB bispectrum caused by a rolling pseudoscalar during inflation, revealing unique signatures in temperature and polarization data that enhance detection prospects.

Contribution

It provides a full-sky formalism computation showing parity-odd and even bispectra signatures from tensor non-Gaussianity, improving detection strategies using polarization data.

Findings

Parity-odd and even bispectra signals are detectable in CMB data.

Inclusion of polarization improves detection sensitivity by up to 400%.

B-mode bispectrum signals could increase the signal-to-noise ratio by 1000 times.

Abstract

We investigate parity-violating signatures of temperature and polarization bispectra of the cosmic microwave background (CMB) in an inflationary model where a rolling pseudoscalar produces large equilateral tensor non-Gaussianity. By a concrete computation based on full-sky formalism, it is shown that resultant CMB bispectra have nonzero signals in both parity-even $(\ell_1 + \ell_2 + \ell_3 = {\rm even})$ and parity-odd $(\ell_1 + \ell_2 + \ell_3 = {\rm odd})$ spaces, and are almost uncorrelated with usual scalar-mode equilateral bispectra. These characteristic signatures and polarization information help to detect such tensor non-Gaussianity. Use of both temperature and E-mode bispectra potentially improves of $400\%$ the detectability with respect to an analysis with temperature bispectrum alone. Considering B-mode bispectrum, the signal-to-noise ratio may be able to increase by 3 orders of magnitude. We present the $1\sigma$ uncertainties of a parameter depending on a coupling constant and a rolling condition for the pseudoscalar expected in the ${\it Planck}$ and the proposed PRISM experiments.