Testing physical models for dipolar asymmetry: from temperature to k space to lensing

Abstract

One of the most intriguing hints of a departure from the standard cosmological model is a large-scale dipolar power asymmetry in the cosmic microwave background (CMB). If not a statistical fluke, its origins must lie in the modulation of the position-space fluctuations via a physical mechanism, which requires the observation of new modes to confirm or refute. We introduce an approach to describe such a modulation in k space and calculate its effects on the CMB temperature and lensing. We fit the k-space modulation parameters to Planck 2015 temperature data and show that CMB lensing will not provide us with enough independent information to confirm or refute such a mechanism. However, our approach elucidates some poorly understood aspects of the asymmetry, in particular that it is weakly constrained. Also, it will be particularly useful in predicting the effectiveness of polarization in testing a physical modulation.

15 pages, 5 figures; max likelihood values corrected, conclusions unchanged; version published in Phys. Rev. D

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• Joint Bayesian analysis of large angular scale CMB temperature anomalies
• Hemispherical Power Asymmetry in intensity and polarization for Planck PR4 data
• Scale-dependent dipolar modulation and the quadrupole-octopole alignment in the CMB temperature
• Primordial anisotropies from cosmic strings during inflation
• Testing the scale-dependent hemispherical asymmetry with the 21-cm power spectrum from the epoch of reionization
• A Pixel Space Method for Testing Dipole Modulation in the CMB Polarization
• A forecast for the detection of the power asymmetry from galaxy surveys
• Anisotropic power spectrum and the observed low-l power in PLANCK CMB data
• Closing in on the large-scale CMB power asymmetry
• 21-cm power spectrum and ionization bias as a probe of long-mode modulated non Gaussian sky
• Addressing Dipole Tension via Clustering in $\Lambda$CDM and beyond