Searching for anisotropic cosmic birefringence with polarization data from SPTpol

The authors report on a search for cosmic birefringence in a region of the southern sky, with the South Pole Telescope. They reconstruct a map of cosmic polarization rotation anisotropies and measure the angular power spectrum of the map, finding it to be consistent with zero. This non detection is used to place constraints on the strength of primordial magnetic fields and of the coupling constant of the electromagnetic Chern-Simons term.