Speaker
Description
When coupled to electromagnetism via a Chern-Simons interaction, axion-like particles (ALP) produce a rotation of the plane of linear polarization of photons known as cosmic birefringence. Recent measurements of cosmic birefringence obtained from the polarization of the cosmic microwave background (CMB) hint at the existence of an isotropic birefringence angle of $\beta\approx0.3^\circ$. Although it is still under scrutiny for its dependence on the modeling of Galactic dust emission, these results currently exclude $\beta=0$ with a statistical significance of $3.6\sigma$.
Such measurements were focused on small-scale polarization data, but further insight can be gained from the study of large-scale information. As the birefringence rotation is proportional to the evolution of the ALP field during the flight of photons, the CMB photons emitted during reionization might experience a different rotation than those emitted during recombination. Therefore, a combined study of large- and small-scale CMB data provides a tomographic view into the ALP field.
In this talk, I will discuss the extension of the methodology to large-scale polarization data, reviewing the impact that instrumental systematics and Galactic dust have in the measurement of isotropic cosmic birefringence. I will also show preliminary results on the measurement of birefringence from the epoch of reionization using Planck data.
