Inflationary power asymmetry from primordial domain walls

TL;DR

This paper proposes a model where primordial domain walls during inflation cause anisotropic fluctuations, explaining observed CMB power asymmetries, especially the dominant dipole, and provides analytic tools for future data analysis.

Contribution

The paper introduces a novel inflationary model with domain walls that produce specific anisotropic signatures in the CMB power spectrum, matching observed asymmetries.

Findings

Model explains the observed CMB power asymmetry including the dominant dipole.

Analytic expressions for CMB covariance corrections are derived.

The model fits data when the CMB sphere does not intersect the domain wall during inflation.

Abstract

We study the asymmetric primordial fluctuations in a model of inflation in which translational invariance is broken by a domain wall. We calculate the corrections to the power spectrum of curvature perturbations; they are anisotropic and contain dipole, quadrupole, and higher multipoles with non-trivial scale-dependent amplitudes. Inspired by observations of these multipole asymmetries in terms of two-point correlations and variance in real space, we demonstrate that this model can explain the observed anomalous power asymmetry of the cosmic microwave background (CMB) sky, including its characteristic feature that the dipole dominates over higher multipoles. We test the viability of the model and place approximate constraints on its parameters by using observational values of dipole, quadrupole, and octopole amplitudes of the asymmetry measured by a local-variance estimator. We find that a configuration of the model in which the CMB sphere does not intersect the domain wall during inflation provides a good fit to the data. We further derive analytic expressions for the corrections to the CMB temperature covariance matrix, or angular power spectra, which can be used in future statistical analysis of the model in spherical harmonic space.