The cross-correlation between the cosmic microwave background (CMB) E- and B-mode polarization can be used to probe parity-violating physics in the Universe. Parity-violating processes such as a Chern-Simons coupling to axion-like particles or the Faraday rotation induced by primordial magnetic fields are expected to rotate the plane of linear polarization and produce a non-null EB correlation. We commonly refer to that rotation as cosmic birefringence.
Past attempts at measuring isotropic cosmic birefringence tended to be dominated by systematic uncertainties and the limited precision of polarization angle calibration. Recently, a novel methodology has overcome the limitation imposed by the insufficient knowledge of instrument calibration by calibrating against Galactic foreground emission. When applied to Planck and WMAP data, this technique hints at the existence of an isotropic β≈0.34º±0.09º birefringence angle. Although it is still under scrutiny for its dependence on the modeling of Galactic dust emission, these results currently exclude β=0 with a statistical significance of 3.6σ.
In this talk, the speaker will review the current state of birefringence measurements from CMB polarization data, commenting on the impact of instrumental systematics and Galactic dust on the analysis. As the significance of the measurement continues to increase, she will also discuss the potential physical origin of the signal, focusing on axion-like particles as the most likely candidate.
頻道：Zoom ID:421-480-1692 ← cosmology
講者：Patricia Diego Palazuelos (Cantabria Inst. of Phys. and Cantabria University, Santander, Spain)
“Copernicus Webinar and Colloquium Series”: To promote scientific discussions during this pandemic, they are organizing an online seminar series, i.e. Copernicus Webinar Series, seeking the most outstanding speakers to introduce innovative ideas and important progress in the field of gravity and cosmology. This series is named after the famous Polish Astronomer, Nicolaus Copernicus, whose discovery eventually marked the dawn of modern science.