General Radiation Spectrum of a Kerr-Newman Black Hole

We extend the classical Damour-Ruffini method and discuss the Hawking radiation from a Kerr-Newman black hole, under the condition that the total energy, angular momentum, and electric charge of spacetime are conserved, but the angular momentum a = J/M per unit mass of the black hole is variable. Taking the reaction of the radiation to the spacetime into consideration, we define the tortoise coordinate transformation and discuss the black hole radiation spectrum. We derive the radiation spectrum that satisfies the unitary principle in the general case.