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arXiv · 1805.00037

Statistical anisotropies in temperature and polarization fluctuations from a scale-dependent trispectrum

Saroj Adhikari·Anne-Sylvie Deutsch·Sarah Shandera
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Abstract

We study statistical anisotropies generated in the observed two-point function of the cosmic microwave background (CMB) fluctuations if the primordial statistics are non-Gaussian. Focusing on the dipole modulations of the anisotropies, we find that the hemispherical power asymmetry observed in the CMB temperature fluctuations can be modeled by a local-type trispectrum with amplitude $\tau_{\rm NL}(k_p=0.05~{\rm Mpc}^{-1}) \approx 2 \times 10^4$ and a large red tilt $n\approx -0.68$. We numerically evaluate the non-Gaussian covariance of the modulation estimators for both temperature and E-mode polarization fluctuations and discuss the prospects of constraining the model using Planck satellite data. We then discuss other effects of the scale-dependent trispectrum that could be used to distinguish this scenario from other explanations of the power asymmetry: higher-order modulations of the two-point function and the non-Gaussian angular power spectrum covariance. As an important consequence of the non-Gaussian power spectrum covariance, we discuss how the CMB-inferred spectral index of primordial scalar fluctuations can be significantly biased in the presence of a scale-dependent local-type trispectrum.

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Saroj Adhikari, Anne-Sylvie Deutsch, Sarah Shandera. 2018-04-30. Statistical anisotropies in temperature and polarization fluctuations from a scale-dependent trispectrum. https://doi.org/10.1103/physrevd.98.023520

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