11,491 research outputs found
Influence of nonuniform critical current density profile on magnetic field behavior of AC susceptibility in 2D Josephson Junction Arrays
Employing mutual-inductance measurements we study the magnetic field
dependence of complex AC susceptibility of artificially prepared highly ordered
(periodic) two-dimensional Josephson junction arrays of unshunted Nb-AlO_x-Nb
junctions. The observed behavior can be explained assuming single-plaquette
approximation of the overdamped model with an inhomogeneous critical current
distribution within a single junction.Comment: 4 pages (REVTEX), 6 figure
Complex evolution of the electronic structure from polycrystalline to monocrystalline graphene: generation of a new Dirac point
First principles calculations, employed to address the properties of
polycrystalline graphene, indicate that the electronic structure of tilt grain
boundaries in this system displays a rather complex evolution towards graphene
bulk, as the tilt angle decreases, with the generation of a new Dirac point at
the Fermi level, and an anisotropic Dirac cone of low energy excitations.
Moreover, the usual Dirac point at the {\bf K} point falls below the Fermi
level, and rises towards it as the tilt angle decreases. Further, our
calculations indicate that the grain-boundary formation energy behaves
non-monotonically with the tilt angle, due to a change in the the spatial
distribution and relative contributions of the bond-stretching and bond-bending
deformations associated with the formation of the defect.Comment: 4 pages (+ a few references on 5th page). Contains text (.tex) file +
4 figures + pdf fil
Magnetic remanence of Josephson junction arrays
In this work we study the magnetic remanence exhibited by Josephson junction
arrays in response to an excitation with an AC magnetic field. The effect,
predicted by numerical simulations to occur in a range of temperatures, is
clearly seen in our tridimensional disordered arrays. We also discuss the
influence of the critical current distribution on the temperature interval
within which the array develops a magnetic remanence. This effect can be used
to determine the critical current distribution of an array.Comment: 8 pages, 4 figures, Talk to be presented on 44th Annual Conference on
Magnetism & Magnetic Materials, San Jose, CA, USA Accepted to be published in
Journal of Applied Physic
Dynamical seesaw mechanism for Dirac neutrinos
So far we have not been able to establish that, as theoretically expected,
neutrinos are their own anti-particles. Here we propose a dynamical way to
account for the Dirac nature of neutrinos and the smallness of their mass in
terms of a new variant of the seesaw paradigm in which the energy scale of
neutrino mass generation could be accessible to the current LHC experiments.Comment: 7 pages, 1 figur
Three-family left-right symmetry with low-scale seesaw mechanism
We suggest a new left-right symmetric model implementing a low-scale seesaw
mechanism in which quantum consistency requires three families of fermions. The
symmetry breaking route to the Standard Model determines the profile of the
"next" expected new physics, characterized either by the simplest left-right
gauge symmetry or by the 3-3-1 scenario. The resulting gauge bosons
can be probed at the LHC and provide a production portal for the right-handed
neutrinos. On the other hand, its flavor changing interactions would affect the
K, D and B neutral meson systems.Comment: 10 pages, 2 figures. Revised version as accepted by JHE
String completion of an electroweak model
The extended electroweak
symmetry framework "explaining" the number of fermion families is revisited.
While -based schemes can not easily be unified within the conventional
field theory sense, we show how to do it within an approach based on D-branes
and (un)oriented open strings, on Calabi-Yau singularities. We show how the
theory can be UV-completed in a quiver setup, free of gauge and string
anomalies. Lepton and baryon numbers are perturbatively conserved, so neutrinos
are Dirac-type, and their lightness results from a novel TeV scale seesaw
mechanism. Dynamical violation of baryon number by exotic instantons could
induce neutron-antineutron oscillations, with proton decay and other dangerous
R-parity violating processes strictly forbidden.Comment: 12 pages, 2 figures, published versio
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