6,734 research outputs found
Measurements of critical current diffraction patterns in annular Josephson junctions
We report systematic measurements of the critical current versus magnetic
field patterns of annular Josephson junctions in a wide magnetic field range. A
modulation of the envelope of the pattern, which depends on the junction width,
is observed. The data are compared with theory and good agreement is found.Comment: 4 pages, 5 figure
Current distribution in a parallel configuration superconducting strip-line detector
Superconducting detectors based on parallel microscopic strip-lines are promising candidates for single molecule detection in time-of-flight mass spectrometry. The device physics of this configuration is complex. In this letter, we employ nano-optical techniques to study the variation of current density, count rate, and pulse amplitude transversely across the parallel strip device. Using the phenomenological London theory, we are able to correlate our results to a non-uniform current distribution between the strips, governed by the London magnetic penetration depth. This fresh perspective convincingly explains anomalous behaviour in large area parallel superconducting strip-line detectors reported in previous studies
A WZW model based on a non-semi-simple group
We present a conformal field theory which desribes a homogeneous four
dimensional Lorentz-signature space-time. The model is an ungauged WZW model
based on a central extension of the Poincar\'e algebra. The central charge of
this theory is exactly four, just like four dimensional Minkowski space. The
model can be interpreted as a four dimensional monochromatic plane wave. As
there are three commuting isometries, other interesting geometries are expected
to emerge via duality.Comment: 8 pages, phyzzx, IASSNS-HEP-93/61 Texable versio
Sensitivity and spatial resolution of square loop SQUID magnetometers
We calculate the flux threading the pick-up coil of a square SQUID
magnetometer in the presence of a current dipole source. The result reproduces
that of a circle coil magnetometer calculated by Wikswo with only small
differences. However it has a simpler form so that it is possible to derive
from it closed form expressions for the current dipole sensitivity and the
spatial resolution. The results are useful to assess the overall performance of
the device and to compare different designs
Assetto geomorfologico dell’area marina di Sinuessa ed ipotesi di fruizione sostenibile
Studio geomorfologico dell’area costiera di Sinuessa (Golfo di Gaeta) che ha consentito di individuare l’approdo di epoca romana di Sinuessa; la ricostruzione dell’evoluzione geomorfologica e tettonica recente dell’area ha reso possibile l’individuazione delle cause della sommersione dell’approdo. L’intenso sviluppo insediativo che oggi caratterizza il tratto di litorale prospiciente l’area spinge a sviluppare un sistema di gestione integrato volto alla valorizzazione dell’area
Effective gluon mass and infrared fixed point in QCD
We report on a special type of solutions for the gluon propagator of pure
QCD, obtained from the corresponding non-linear Schwinger-Dyson equation
formulated in the Feynman gauge of the background field method. These solutions
reach a finite value in the deep infrared and may be fitted using a massive
propagator, with the crucial characteristic that the effective ``mass''
employed depends on the momentum transfer. Specifically, the gluon mass falls
off as the inverse square of the momentum, as expected from the
operator-product expansion. In addition, one may define a dimensionless
quantity, which constitutes the generalization in a non-Abelian context of the
universal QED effective charge. This strong effective charge displays
asymptotic freedom in the ultraviolet whereas in the low-energy regime it
freezes at a finite value, giving rise to an infrared fixed point for QCD.Comment: 6 pages, 2 figures, Talk given at QCD@work 2007, Martina Franca,
Italy, 16-20 June 200
Secondary Baryon Asymmetry in pi(+-)p Collisions
The process of secondary baryon production in pi(+-)p collisions at high
energies in the central and forward fragmentation regions is considered in the
framework of the Quark-Gluon String Model. The contribution of the
string-junction mechanism to the baryon production is analysed. The results of
numerical calculations are in reasonable agreement with the experimental data
on the Lambda/bar(Lambda) and p/bar(p)$ asymmetries.Comment: Contribution to the Proceedings of QCD@Work 2007, International
Workshop on Quantum Chromodynamics, Theory and Experiment, Martina
Franca-Valle d'Itria, Italy, June 16-20, 2007 (6 pages and 4 figures
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