# Signals From the Epoch of Cosmological Recombination

## TL;DR

This paper reviews the physical processes during cosmological recombination and their impact on the Cosmic Microwave Background, emphasizing the detailed physics of hydrogen and helium recombination and their observable consequences.

## Contribution

It provides a concise overview of the physics of cosmological recombination and highlights recent detailed studies on hydrogen and helium recombination processes.

## Key findings

- Recombination physics is simple yet allows for detailed modeling.
- Physical processes during recombination affect CMB energy spectrum and anisotropies.
- Recent studies have refined understanding of hydrogen and helium recombination.

## Abstract

The physical ingredients to describe the epoch of cosmological recombination are amazingly simple and well-understood. This fact allows us to take into account a very large variety of physical processes, still finding potentially measurable consequences for the energy spectrum and temperature anisotropies of the Cosmic Microwave Background (CMB). In this contribution we provide a short historical overview in connection with the cosmological recombination epoch and its connection to the CMB. Also we highlight some of the detailed physics that were studied over the past few years in the context of the cosmological recombination of hydrogen and helium. (abrigded)