Density matrix and generating functional for quantized neutrino field in the space-time of a rotating black hole

The problem of calculating the density matrix that describes processes of creation, absorption, and scattering of particles (neutrinos and antineutrinos) by a rotating black hole is solved. This result is used to construct a generating functional that makes it possible to describe in a unified manner these quantum processes in an external field, and also to investigate the spectra, correlation functions, and expectation values of a number of observables for different choices of the initial state of the system