The Polarization of the Cosmic Microwave Background

TL;DR

This paper reviews how the Cosmic Microwave Background (CMB) becomes polarized, the implications of polarization for testing inflation, and the effects of gravitational lensing and reionization on CMB polarization.

Contribution

It provides a comprehensive summary of the physical mechanisms behind CMB polarization and its use in probing early universe physics.

Findings

Polarization arises from Thomson scattering during recombination.

Gravitational waves leave an imprint on CMB polarization.

Post-recombination processes like lensing and reionization modify polarization signals.

Abstract

We summarize the physical mechanism by which the Cosmic Microwave Background acquires a small degree of polarization. We discuss the imprint left by gravitational waves and the use of polarization as a test of the inflationary paradigm. We discuss some physical processes that affect the CMB polarization after recombination such as gravitational lensing and the reionization of the universe.