Scale-dependent hemispherical asymmetry from general initial state during inflation

Abstract

We consider a general initial state for inflation as the mechanism for generating scale-dependent hemispherical asymmetry. An observable scale-dependent non-Gaussianity is generated that leads to observable hemispherical asymmetry from the super-horizon long mode modulation. We show that the amplitude of dipole asymmetry falls off exponentially on small angular scales which can address the absence of dipole asymmetry at these scales.In addition, depending on the nature of non-vaccum initial state, the amplitude of the dipole asymmetry has oscillatory features which can be detected in a careful CMB map analysis. Furthermore, we show that the non-vacuum initial state provides a natural mechanism for enhancing the super horizon long mode perturbation as required to generate the dipole asymmetry.

(v1) 16 pages, 3 figures; (v2) 17 pages, more clarifications, discussions and references, to appear in Journal of Cosmology and Astroparticle Physics

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• Pre-inflationary primordial perturbations
• Expected dipole asymmetry in CMB polarization
• CMB hemispherical asymmetry from non-linear isocurvature perturbations
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• Isotropic non-Gaussian $g_{\mathrm{NL}}$-like toy models that reproduce the cosmic microwave background anomalies