  A new theoretical framework, based on the quantum field theory of open
systems applied to neutrinos, has been developed to describe the neutrino
evolution in external environments accounting for the effect of the neutrino
quantum decoherence. The developed new approach enables one to obtain the
explicit expressions of the decoherence and relaxation parameters that account
for a particular process, in which the neutrino participates, and also for the
characteristics of an external environment and of the neutrino itself,
including the neutrino energy. We have used this approach to consider a new
mechanism of the neutrino quantum decoherence engendered by the neutrino
radiative decay to photons and dark photons in an astrophysical environment.
The importance of the performed studies is highlighted by the prospects of the
forthcoming new large volume neutrino detectors that will provide new frontier
in high-statistics measurements of neutrino fluxes from supernovae.
