Dependence of the Cosmic Microwave Background Lensing Power Spectrum on the Matter Density

TL;DR

This paper explains how the gravitational lensing of CMB anisotropies depends on the matter density, highlighting the role of the matter power spectrum and potential decay before matter-radiation equality.

Contribution

It provides an analytic understanding of the dependence of CMB lensing on matter density, focusing on the influence of small-scale potential decay.

Findings

Lensing depends mainly on the shape of the matter power spectrum.

Decay of small-scale potentials influences lensing signals.

Analytic explanation clarifies the matter density's role in CMB lensing.

Abstract

The anisotropies in the cosmic microwave background (CMB) provide our best laboratory for testing models of the formation and evolution of large-scale structure. The rich features in the cosmic microwave background anisotropy spectrum, in combination with highly precise observations and theoretical predictions, also allow us to simultaneously constrain a number of cosmological parameters. As observations have progressed, measurements at smaller angular scales have provided increasing leverage. These smaller angular scales provide sensitive measures of the matter density through the effect of gravitational lensing. In this work we provide an analytic explanation of the manner in which the lensing of CMB anisotropies depends on the matter density, finding that the dominant effect comes from the shape of the matter power spectrum set by the decay of small-scale potentials between horizon crossing and matter-radiation equality.