Abstract
Upcoming cosmic microwave background (CMB) data can be used to explore harmonic 3-point functions that involve the B-mode component of the CMB polarization signal. We focus on bispectra describing the non-Gaussian correlation of the B-mode field and the CMB temperature anisotropies (T) and/or E-mode polarization, i.e. <TTB>, <EEB>, and <TEB>. Such bispectra probe violations of the tensor consistency relation: the model-independent behavior of cosmological correlation functions that involve a large-wavelength tensor mode (gravitational wave). An observed violation of the tensor consistency relation would exclude a large number of inflation models. We describe a generalization of the Komatsu-Spergel-Wandelt (KSW) bispectrum estimator that allows statistical inference on this type of primordial non-Gaussianity with data of the CMB temperature and polarization anisotropies. The generalized estimator shares its statistical properties with the existing KSW estimator and retains the favorable numerical scaling with angular resolution. In this paper we derive the estimator and present a set of Fisher forecasts. We show how the forecasts scale with various experimental parameters such as lower and upper angular band-limit, relevant for e.g. the upcoming ground-based Simons Observatory experiment and proposed LiteBIRD satellite experiment. We comment on possible contaminants due to secondary cosmological and astrophysical sources.
Highlights
Inflationary cosmology was proposed [1,2,3] to solve several cosmological puzzles: an early period of accelerated expansion explains the homogeneity, isotropy, and flatness of the Universe, as well as the lack of relic monopoles
Tensor modes produced during inflation lead to primordial gravitational waves that are potentially detectable in the polarization of the cosmic microwave
This paper focuses on bispectra, the harmonic equivalent of 3-point correlation functions, that describe how a single B-mode perturbation is correlated to perturbations in the E-mode field or the cosmic microwave background (CMB) temperature, i.e., the hTTBi, hEEBi, and hTEBi bispectra
Summary
Inflationary cosmology was proposed [1,2,3] to solve several cosmological puzzles: an early period of accelerated expansion explains the homogeneity, isotropy, and flatness of the Universe, as well as the lack of relic monopoles. A detection of a significant ζζζ correlation in the squeezed limit would experimentally rule out the validity of the consistency relation and would provide evidence for the presence of more than one time-evolving scalar field during inflation. Unlike T, current B-mode observations are not cosmicvariance limited; sensitivity to primordial tensor perturbations can significantly increase with B-mode polarization data [47] For these reasons, this paper focuses on bispectra, the harmonic equivalent of 3-point correlation functions, that describe how a single B-mode perturbation is correlated to perturbations in the E-mode field or the CMB temperature, i.e., the hTTBi, hEEBi, and hTEBi bispectra. To illustrate the potential of the generalized estimator for testing the tensor consistency relation we provide a number of Fisher forecasts that represent idealized experimental outcomes These forecasts demonstrate the lmin and lmax dependence of constraints on the amplitude of the squeezed ζζh correlation.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
