Electromagnetic duality anomaly in accelerating waveguides

Abstract: The classical symmetry of the source-free Maxwell equations under electric-magnetic duality rotations leads to a conserved Noether charge, corresponding to the circular polarization of light. We show that, in quantum field theory, the vacuum expectation value of this charge is no longer time-independent inside a long, cylindrical waveguide undergoing both linear and rotational acceleration from rest. Specifically, photon pairs are spontaneously excited from the quantum vacuum by the accelerated background, while the helical motion induces an imbalance in the number of right- and left-handed modes produced. This photon helicity non-conservation reflects a genuine quantum effect that breaks the classical duality symmetry. The model considered paves the way for experimental studies.