6,228 research outputs found
Radiative transitions of high energy neutrino in dense matter
The quantum theory of the ``spin light'' (electromagnetic radiation emitted
by a massive neutrino propagating in dense matter due to the weak interaction
of a neutrino with background fermions) is developed. In contrast to the
Cherenkov radiation, this effect does not disappear even if the medium
refractive index is assumed to be equal to unity. The formulas for the
transition rate and the total radiation power are obtained. It is found out
that radiation of photons is possible only when the sign of the particle
helicity is opposite to that of the effective potential describing the
interaction of a neutrino (antineutrino) with the background medium. Due to the
radiative self-polarization the radiating particle can change its helicity. As
a result, the active left-handed polarized neutrino (right-handed polarized
antineutrino) converting to the state with inverse helicity can become
practically ``sterile''. Since the sign of the effective potential depends on
the neutrino flavor and the matter structure, the ``spin light'' can change a
ratio of active neutrinos of different flavors. In the ultra relativistic
approach, the radiated photons averaged energy is equal to one third of the
initial neutrino energy, and two thirds of the energy are carried out by the
final ``sterile'' neutrinos. This fact can be important for the understanding
of the ``dark matter'' formation mechanism on the early stages of evolution of
the Universe.Comment: 7 pages, latex, one misprint in eq. 12 correcte
Mergers and binary systems of SMBH in the contexts of nuclear activity and galaxy evolution
The dynamic evolution of binary systems of supermassive black holes (SMBH)
may be a key factor affecting a large fraction of the observed properties of
active galactic nuclei (AGN) and galaxy evolution. Different classes of AGN can
be related in general to four evolutionary stages in a binary SMBH: 1) early
merger stage; 2) wide pair stage; 3) close pair stage; and 4) pre-coalescence
stage. This scheme can explain a variety of properties of AGN: radio and
optical luminosity differences between different classes of AGN, long-term and
short-term variability, quasi-periodic nuclear flares, recurrent formation of
relativistic outflows in AGN and their apparent morphology and kinematics.Comment: 2 pages, no figures; to be published in Proceedings of the Conference
"Growing Black Holes", Garching, Germany June 21-25, 2004, edited by
A.Merloni, S.Nayakshin, R.Sunyaev (Springer-Verlag series of ESO Astrophysic
Resonance enhancement of neutrino oscillations due to transition magnetic moments
Studying neutrino propagation in static background of dense matter and
electromagnetic field [1] we obtained that the resonance enhancement of
neutrino oscillations due to transition magnetic moments is possible. In this
work we calculate the probabilities of spin-flavor transitions using solutions
of the neutrino evolution equation in slowly varying magnetic field within the
adiabatic approximation. We find that the resonance behavior of the transition
probabilities is strictly connected to the neutrino polarization.Comment: 8 pages, 2 figures, LaTe
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