Entropy of the Dirac field in a Kerr-Newman black hole - art. no. 063003

Thinking of the Dirac equations in Newman-Penrose formalism, there are four components of the wave function Psi(11),Psi(12),Psi(21),Psi(22). We consid er that the total free energy is summed up from the free energies of the fo ur components. Then the entropy of the Dirac field in a Kerr-Newman black h ole is calculated via the brick-wall method. We find that the calculation o f the Dirac field is similar to that of a scalar field. It also requires a radial and an angular cutoff epsilon and delta. Moreover, if the cutoff val ues <(epsilon)over bar> and delta satisfy the same proper relation in the s calar field between them, the resulting entropy is 7/2 times the Klein-Gord on field.