Noether currents of charged spherical black holes - art. no. 064024

We calculate the Noether currents and charges for the Einstein-Maxwell theo ry using a version of the Wald approach. In spherical symmetry, the choice of time can be taken as the Kodama vector. For the static case, the resulti ng combined Einstein-Maxwell charge is just the mass of the black hole. Usi ng either a classically defined entropy or the Iyer-Wald selection rules, t he entropy is found to be just a quarter of the area of the trapping horizo n. We propose identifying the combined Noether charge as an energy associat ed with the Kodama time. For the extremal black hole case, we discuss the p roblem of Wald's rescaling of the surface gravity to define the entropy.