Probing Dark Matter Isocurvature with Primordial Non-Gaussianity

Abstract

Multiple fields can become dynamical during the inflationary epoch. We consider an example where a light field acquires isocurvature fluctuations during inflation and contributes to the dark matter abundance at late times. Interactions between the light field and the adiabatic sector contribute to mixed adiabatic-isocurvature non-Gaussianity (NG). We show the resulting form of NG has a different kinematic dependence than the 'local shape' commonly considered, and highlight the parameter space where a dedicated search is expected to significantly improve the current $\text{Planck}$ sensitivity. We interpret our results in the context of the QCD axion and illustrate how the proposed NG searches can improve upon the existing searches for isocurvature power spectrum and bispectrum.

17 pages, 4 figures

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• The Effective Field Theory of Inflation
• Primordial Non-Gaussianities from Inflation Models
• Cosmological Collider Physics
• The shape of primordial non-Gaussianity and the CMB bispectrum
• Upper Limit on the QCD Axion Mass from Isolated Neutron Star Cooling
• Limits on Isocurvature Perturbations from Non-Gaussianity in WMAP Temperature Anisotropies
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Cited by in corpus (1)

• Non-Gaussianity from explicit $U(1)$-breaking interactions