  In this paper, we study the spin transitions of neutrinos caused by the
interaction with a gravitational field. We consider a model with a scalar field
(describing screening effects) conformally coupled to matter and neutrinos. The
presence of screening effects suppresses the neutrino spin-flip probability as
compared with General Relativity predictions. Such a result could be used,
combined with neutrino astronomy, for testing modified theories of gravity and,
in turn, screening effects invoked to bypass the solar system and Lab tests.
Such an analysis has been also extended to the case of the quintessence field
surrounding a black hole. Here we investigate the flavor and spin transitions,
showing that also in such a case exists a suppression of the effect compared to
General Relativity prediction.
