  Using the complete classification of the bases in the rotating black hole
background we separate superradiance from the Hawking effect. We first find
that there is spontaneous particle creation for fermions by the potential
outside the black hole horizon for the frequencies inside the superradiant
regime, i.e. $\omega<k\Omega_H$. However, these particles do not enhance the
total flux from the black hole. For the superradiance particle to became real,
its negative energy counterpart has to be canceled by the positive energy
Hawking radiation mode at the horizon. Since due to the Pauli's principle this
cancellation must be one-to-one, the superradiance effect cannot add anything
to the total black hole flux. For an extremal black hole, the Hawking
temperature is zero, horizon is not populated with thermal modes, and fermions
can be emitted through the superradiance mechanism. On the other hand, a
macroscopic flux of fermions infalling to the black hole is the opposite
process of Hawking radiation. A positive energy-infalling particle must cancel
out a negative energy thermal mode at the horizon, which leaves a net positive
energy mode that crosses the horizon. Since there is finite thermal particle
density at the horizon, this implies that there is a maximal fermion infalling
rate which is also controlled by the Hawking temperature.

General Relativity and Quantum Cosmology;High Energy Physics - Theory