Near-horizon symmetries in Einstein–Maxwell theory

Abstract This manuscript aims to provide a comprehensive derivation of the Einstein–Maxwell charges and fluxes in the near-horizon region of a four-dimensional non-extremal black hole, with vanishing cosmological constant. Specifically, we present a detailed derivation of the Noether charges within both the metric and first-order formulations, elucidating the relationship between the Carrollian internal boost charge and the Lorentz boost charge. It is well-established in the literature that Carrollian fluids exhibit an internal local boost symmetry; we demonstrate that this symmetry precisely corresponds to a Lorentz internal transformation. Finally, we prove that the near-horizon Einstein equations can be obtained from the flux-balance law by employing the generalized Barnich–Troessaert bracket.