Can Relic Superhorizon Inhomogeneities be Responsible for Large-Scale CMB Anomalies?

Abstract

We investigate the effects of the presence of relic classical superhorizon inhomogeneities during inflation. This superhorizon inhomogeneity appears as a gradient locally and picks out a preferred direction. Quantum fluctuations on this slightly inhomogeneous background are generally statistical anisotropic. We find a quadrupole modification to the ordinary isotropic spectrum. Moreover, this deviation from statistical isotropy is scale-dependent, with a $\sim -1/k^2$ factor. This result implies that the statistical anisotropy mainly appears on large scales, while the spectrum on small scales remains highly isotropic. Moreover, due to this $-1/k^2$ factor, the power on large scales is suppressed. Thus, our model can simultaneously explain the observed anisotropic alignments of the low-$\ell$ multipoles and their low power.

5 pages, 4 figures, v2 references added in; v3 to match the published version

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Cited by in corpus (13)

• Non-isotropy in the CMB power spectrum in single field inflation
• Primordial perturbations and non-Gaussianities in Hořava-Lifshitz gravity
• CMB Power Asymmetry from Primordial Sound Speed Parameter
• Primordial Non-Gaussianities from the Trispectra in Multiple Field Inflationary Models
• Primordial non-Gaussianity and power asymmetry with quantum gravitational effects in loop quantum cosmology
• Dipole Modulation of Cosmic Microwave Background Temperature and Polarization
• Relating the inhomogeneous power spectrum to the CMB hemispherical anisotropy
• Erratum: Statistical anisotropy in the inflationary universe
• An analytic approach to perturbations from an initially anisotropic universe
• Dark Energy Cosmology with the Alternative Cosmic Microwave Background Data
• Noncommutative Geometry and the Primordial Dipolar Imaginary Power Spectrum
• Probing Cosmology beyond $\Lambda$CDM using the SKA
• Primordial gravitational waves and perturbations during an inhomogeneous inflation