  As is well recognized, the supernova explosions produce a great amount of
neutrinos, thus we have a strong reason to believe that all violent
cosmological events, such as supernova explosions, gamma bursts, black hole
merging or neutron star merging would cause remarkable neutrino sprays into the
open space. Recently, a very high-energy neutrino captured by the IceCube
detector is believed to be radiated from a blazar. However, as the LIGO
collaboration first observed gravitational wave caused by spiral approach and
merging of two giant back holes, the IceCube did not see an excess of
cosmological neutrinos. The reason may be due to that the source is too far
away or the neutrino spectrum is not suitable for the IceCube facility
detection or just missing by chance. In this work, following Hawking's picture,
we suppose that neutrinos would be ejected from black holes as strong
gravitational effects lower the potential barriers to enhance neutrino escape
rate through quantum tunneling effects. We use the Dirac equation in the curved
spacetime to describe the neutrino status and estimate the rejection rate.
Then, we also adopt a simplified version where the effects of curved spacetime
is ignored to clarify the physical picture. Our conclusion is drawn based on
the numerical results and a discussion on the phenomenological consequence is
presented.
