Negative Temperature of Inner Horizon and Planck Absolute Entropy of a Kerr-Newman Black Hole

Considering the contribution of both the outer and inner horizons, the Hamilton-Jacobi method is applied to a Kerr-Newman black hole and a negative temperature of the inner horizon is obtained. Under the negative temperature inside the black hole, the thermodynamics of the two horizons is studied, and the new Bekenstein-Smarr formula is given. The entropies of the inner and outer horizons are all positive. The new entropy expression of the black hole satisfies the Nernst Theorem and can be regarded as the Planck absolute entropy.