Asymmetric Sky from the Long Mode Modulations

TL;DR

This paper explores how long-wavelength mode modulations can generate dipole asymmetries in the CMB, tensor perturbations, and halo bias, revealing a unified mechanism with specific consistency conditions.

Contribution

It uncovers the common mechanism behind multiple cosmological asymmetries and derives consistency conditions relating their amplitudes across different phenomena.

Findings

Long mode modulations produce dipole asymmetries in CMB, tensor perturbations, and halo bias.

The mechanism does not induce asymmetry in the universe's acceleration in ΛCDM.

Derived consistency conditions link the amplitudes of asymmetries across phenomena.

Abstract

The observed dipole asymmetry in Cosmic Microwave Background radiation may have originated from the modulations of super-horizon long wavelength modes. In this work we unveil different aspects of asymmetries generated from the long wavelength mode modulations. We show that the same mechanism which leads to the observed CMB power spectrum dipole asymmetry from the long mode modulations also yields dipole asymmetry in (a): tensor perturbations power spectrum and (b): the halo bias parameter. These are different phenomena relevant to different cosmological histories but both share the same underlying mechanism in generating asymmetries in the sky. We obtain the set of consistency conditions relating the amplitude of dipole asymmetries generated on tensor perturbations and halo bias parameter to the amplitude of dipole asymmetry generated on CMB power spectrum. In addition, we show that this mechanism does not produce dipole asymmetry in acceleration expansion in $\Lambda CDM$ universe because the super-horizon curvature perturbation is conserved in this background.