Lecture notes on the physics of cosmic microwave background anisotropies

TL;DR

This paper reviews the theoretical understanding of cosmic microwave background anisotropies and polarization, highlighting how current observations inform us about the universe's composition, geometry, and early universe physics, including small-scale fluctuations.

Contribution

It provides a comprehensive overview of CMB anisotropy and polarization theory, integrating recent observational insights and discussing future high-resolution measurements.

Findings

CMB observations constrain universe's composition and geometry

Current data support inflationary models of the early universe

Small-scale fluctuations are key targets for upcoming instruments

Abstract

We review the theory of the temperature anisotropy and polarization of the cosmic microwave background (CMB) radiation, and describe what we have learned from current CMB observations. In particular, we discuss how the CMB is being used to provide precise measurements of the composition and geometry of the observable universe, and to constrain the physics of the early universe. We also briefly review the physics of the small-scale CMB fluctuations generated during and after the epoch of reionization, and which are the target of a new breed of arcminute-resolution instruments.