27,335 research outputs found
Neutron Star Astronomy in the era of the European Extremely Large Telescope
About 25 isolated neutron stars (INSs) are now detected in the optical
domain, mainly thanks to the HST and to VLT-class telescopes. The European
Extremely Large Telescope (E-ELT) will yield ~100 new identifications, many of
which from the follow-up of SKA, IXO, and Fermi observations. Moreover, the
E-ELT will allow to carry out, on a much larger sample, INS observations which
still challenge VLT-class telescopes, enabling studies on the structure and
composition of the NS interior, of its atmosphere and magnetosphere, as well as
to search for debris discs. In this contribution, I outline future perspectives
for NS optical astronomy with the E-ELT.Comment: 4 pages, to be published in Proceedings of the Conference
"ASTROphysics of Neutron Stars 2010", a conference in honor of M. Ali Alpar,
held in Cesme (Izmir) August 2-6 201
Emergence of the stochastic resonance in glow discharge plasma
stochastic resonance, glow discharge plasma, excitable medium, absolute mean
differenceComment: St
Interpolated inequalities between exponential and Gaussian, Orlicz hypercontractivity and isoperimetry
We introduce and study a notion of Orlicz hypercontractive semigroups. We
analyze their relations with general -Sobolev inequalities, thus extending
Gross hypercontractivity theory. We provide criteria for these Sobolev type
inequalities and for related properties. In particular, we implement in the
context of probability measures the ideas of Maz'ja's capacity theory, and
present equivalent forms relating the capacity of sets to their measure. Orlicz
hypercontractivity efficiently describes the integrability improving properties
of the Heat semigroup associated to the Boltzmann measures , when . As an application
we derive accurate isoperimetric inequalities for their products. This
completes earlier works by Bobkov-Houdr\'e and Talagrand, and provides a scale
of dimension free isoperimetric inequalities as well as comparison theorems.Comment: 76 pages, 1 figur
Flux Flow Effects in Annular Josephson Tunnel Junctions
We investigate Josephson flux-flow in annular Josephson tunnel junctions
(AJTJs) under the application of magnetic fields generating finite-voltage
steps in their current-voltage characteristics. Experimental data are presented
for confocal AJTJs which are the natural generalization of the well studied
circular AJTJs for which flux flow effects have never been reported. Displaced
linear slopes, Fiske step staircases and Eck steps were sequentially recorded
at with high-quality Nb/Al-AlOx/Nb confocal AJTJs when increasing the
strength of a uniform magnetic field applied in the plane of the junction.
Their amplitude was found to strongly depend not only on the strength, but also
on the orientation, of the external field. Extensive numerical simulations
based on a phenomenological sine-Gordon model developed for confocal AJTJs were
carried out to disclose the basic flux-flow mechanism responsible for the
appearance of magnetically induced steps and to elucidate the role of several
critical parameters, namely, the field orientation, the system loss and the
annulus eccentricity. It was found that in a topologically closed system, such
as the AJTJ, where the number of trapped fluxons is conserved and new fluxons
can be created only in the form of fluxon-antifluxon pairs, the existence of a
steady viscous flow of Josephson vortices only relies on the capability of the
fluxons and antifluxons to be generated and to annihilate each other inside the
junction. This also implies that flux-flow effects are not observable in
circular AJTJs.Comment: 26 pages, 8 figure
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