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Neutrinoless double beta decay with and without Majoron-like boson emission in a 3-3-1 model
We consider the contributions to the neutrinoless double beta decays in a
electroweak model. We show that for a range of the
parameters in the model there are diagrams involving vector-vector-scalar and
trilinear scalar couplings which can be potentially as contributing as the
light massive Majorana neutrino exchange one. We use these contributions to
obtain constraints upon some mass scales of the model, like the masses of the
new charged vector and scalar bosons. We also consider briefly the decay in
which besides the two electrons a Majoron-like boson is emitted.Comment: Revtex, 10 pages and 8 eps figures. Extended version to be published
in Physical Review
Quantum interference oscillations of the superparamagnetic blocking in an Fe8 molecular nanomagnet
We show that the dynamic magnetic susceptibility and the superparamagnetic
blocking temperature of an Fe8 single molecule magnet oscillate as a function
of the magnetic field Hx applied along its hard magnetic axis. These
oscillations are associated with quantum interferences, tuned by Hx, between
different spin tunneling paths linking two excited magnetic states. The
oscillation period is determined by the quantum mixing between the ground S=10
and excited multiplets. These experiments enable us to quantify such mixing. We
find that the weight of excited multiplets in the magnetic ground state of Fe8
amounts to approximately 11.6%.Comment: Accepted in Phys. Rev. Let
Remark on the vectorlike nature of the electromagnetism and the electric charge quantization
In this work we study the structure of the electromagnetic interactions and
the electric charge quantization in gauge theories of electroweak interactions
based on semi-simple groups. We show that in the standard model of the
electroweak interactions the structure of the electromagnetic interactions is
strongly correlated to the quantization pattern of the electric charges. We
examine these two questions also in all possible chiral bilepton gauge models
of the electroweak interactions. In all they we can explain the vectorlike
nature of the electromagnetic interactions and the electric charge quantization
together demanding nonvanishing fermion masses and the anomaly cancellations.Comment: 17 pages, latex, no figure
Influence of self-gravity on the runaway instability of black hole-torus systems
Results from the first fully general relativistic numerical simulations in
axisymmetry of a system formed by a black hole surrounded by a self-gravitating
torus in equilibrium are presented, aiming to assess the influence of the torus
self-gravity on the onset of the runaway instability. We consider several
models with varying torus-to-black hole mass ratio and angular momentum
distribution orbiting in equilibrium around a non-rotating black hole. The tori
are perturbed to induce the mass transfer towards the black hole. Our numerical
simulations show that all models exhibit a persistent phase of axisymmetric
oscillations around their equilibria for several dynamical timescales without
the appearance of the runaway instability, indicating that the self-gravity of
the torus does not play a critical role favoring the onset of the instability,
at least during the first few dynamical timescales.Comment: To appear on Phys.Rev.Let
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