IX Black Hole Workshop

Guimarães 19-20 December 2016

Superradiance is a radiation enhancement process that happens in many contexts in physics. One of its manifestations is what we call superradiant scattering. It is, generally, believed that fermionic fields cannot be superradiantly amplified, whereas bosonic fields can. Nevertheless, there are several examples in nature of fermion systems with bosonic behaviour, for instance, Cooper pairs in Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity and mesons in particle physics. This makes us ask the questions: Is it possible to have a fermion condensate which can exhibit superradiant amplification? Or, is there a non-linear interaction between fermions which enables them to exhibit superradiant amplification? The answer to these questions is of great importance to test the idea that the Penrose process is the particle analogous of superradiant scattering phenomenon. We treat the cases of scalar, Dirac and non-linear Dirac fields scattering on an electrostatic potential barrier and on a black hole background. Also, we give an example of a theory describing a fermion (spin-1/2) condensate that admits superradiant solutions.