CENTRA Seminar - Electromagnetic quantum anomalies and applications to black hole astrophysics - 06 dezembro 2018

Adrian del Rio Vega

CENTRA/IST

Since the discovery of the anomalous non-conservation of the chiral fermion current in 1969 by Adler, Bell and Jackiw, it is known that classical symmetries of field theories may fail to survive the quantization, leading to what is known in the literature as quantum anomalies. By Noether’s theorem this automatically means that certain physical quantities are no longer conserved in time. After briefly introducing the key quantum aspects in curved spacetimes, in this talk I will discuss a new example in the context of quantum electrodynamics and gravity. I will show that electric-magnetic duality rotations are a Noether symmetry of the source-free Maxwell action in curved spacetimes, and however the symmetry is anomalous in the quantum theory due to spacetime curvature. The Noether charge associated with this classical symmetry physically accounts for the polarization state of the electromagnetic field, measuring the net difference between right- and left-handed circularly polarized waves. Due to the anomaly the time-dependence of this charge is now determined by the geometry of the spacetime background. Hence, this anomaly opens up the possibility of getting information from astrophysical black holes through anomalous detections of electromagnetic polarization.