Scale-dependent non-Gaussianity and the CMB Power Asymmetry

Abstract

We introduce an alternative parametrisation for the scale dependence of the non-linearity parameter $f_{\mathrm{NL}}$ in quasi-local models of non-Gaussianity. Our parametrisation remains valid when $f_{\mathrm{NL}}$ changes sign, unlike the commonly adopted power law ansatz $f_{\mathrm{NL}}(k)\propto k^{n_{f_{\mathrm{NL}}}}$. We motivate our alternative parametrisation by appealing to the self-interacting curvaton scenario, and as an application, we apply it to the CMB power asymmetry. Explaining the power asymmetry requires a strongly scale dependent non-Gaussianity. We show that regimes of model parameter space where $f_{\mathrm{NL}}$ is strongly scale dependent are typically associated with a large $g_{\mathrm{NL}}$ and quadrupolar power asymmetry, which can be ruled out by existing observational constraints.

21 pages. Comments welcome. v2: Minor changes and corrections to match the published version

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• The hemispherical asymmetry from a scale-dependent inflationary bispectrum
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• Generalized local ansatz for scale-dependent primordial non-Gaussianities and future galaxy surveys
• Test of the Statistical Isotropy of the Universe using Gravitational Waves