Gauge invariant derivation of zeroth and first laws of black hole thermodynamics

In gauge invariant theories, like Einstein-Maxwell theory, physical observables should be gauge invariant. In particular, mass, entropy, angular momentum, electric charge, and their respective chemical potentials, temperature, horizon angular velocity, and electric potential, which appear in the laws of black hole thermodynamics, should be gauge invariant. In the usual construction of the laws of black hole thermodynamics, gauge invariance of the intensive quantities is subtle; here, we remedy this and provide a gauge invariant derivation and the proof of the zeroth and first laws of black hole thermodynamics.

Automated summary

In gauge invariant theories, physical observables like mass, entropy, angular momentum, electric charge, temperature, horizon angular velocity, and electric potential should be gauge invariant. The construction of the laws of black hole thermodynamics requires subtle consideration of the gauge invariance of intensive quantities.