# The V-mode polarization of the Cosmic Microwave Background

## TL;DR

This paper investigates the V-mode polarization of the Cosmic Microwave Background in a weakly magnetized plasma, highlighting its potential as a new observational tool for probing pre-decoupling physics.

## Contribution

It presents calculations of the VV and VT angular power spectra for V-mode polarization under adiabatic initial conditions, emphasizing the significance of magnetic fields and frequency channels.

## Key findings

- VT power spectra can exceed B-mode polarization by seven orders of magnitude.
- V-mode polarization detection could offer new insights into pre-decoupling physics.
- The study provides theoretical predictions for future observational efforts.

## Abstract

The V-mode polarization of the Cosmic Microwave Background is discussed in a weakly magnetized plasma. The VV and VT angular power spectra are computed for adiabatic initial conditions of the Einstein-Boltzmann hierarchy. Depending upon the frequency channel and upon the magnetic field intensity, the VT power spectra of the circular polarization can even be seven orders of magnitude larger than a putative B-mode polarization stemming from the lensing of the primary anisotropies. Specific programs aimed at the direct detection of the V-mode polarization of the Cosmic Microwave Background could provide a new observational tool for the scrutiny of pre-decoupling physics.