4,146 research outputs found
Polynomial Relations in the Centre of U_q(sl(N))
When the parameter of deformation q is a m-th root of unity, the centre of
U_q(sl(N))$ contains, besides the usual q-deformed Casimirs, a set of new
generators, which are basically the m-th powers of all the Cartan generators of
U_q(sl(N)). All these central elements are however not independent. In this
letter, generalising the well-known case of U_q(sl(2)), we explicitly write
polynomial relations satisfied by the generators of the centre. Application to
the parametrization of irreducible representations and to fusion rules are
sketched.Comment: 8 pages, minor TeXnical revision to allow automatic TeXin
Wavelet entropy of stochastic processes
We compare two different definitions for the wavelet entropy associated to
stochastic processes. The first one, the Normalized Total Wavelet Entropy
(NTWS) family [Phys. Rev. E 57 (1998) 932; J. Neuroscience Method 105 (2001)
65; Physica A (2005) in press] and a second introduced by Tavares and Lucena
[Physica A 357 (2005)~71]. In order to understand their advantages and
disadvantages, exact results obtained for fractional Gaussian noise (-1<alpha<
1) and the fractional Brownian motion (1 < alpha < 3) are assessed. We find out
that NTWS family performs better as a characterization method for these
stochastic processes.Comment: 12 pages, 4 figures, submitted to Physica
Characterization of laser propagation through turbulent media by quantifiers based on the wavelet transform: dynamic study
We analyze, within the wavelet theory framework, the wandering over a screen
of the centroid of a laser beam after it has propagated through a time-changing
laboratory-generated turbulence. Following a previous work (Fractals 12 (2004)
223) two quantifiers are used, the Hurst parameter, , and the Normalized
Total Wavelet Entropy, . The temporal evolution of both
quantifiers, obtained from the laser spot data stream is studied and compared.
This allows us to extract information of the stochastic process associated to
the turbulence dynamics.Comment: 11 pages, 3 figures, accepted to be published in Physica
Analysis of Electrical Coupling Parameters in Superconducting Cables
The analysis of current distribution and redistribution in superconducting cables requires the knowledge of the electric coupling among strands, and in particular the interstrand resistance and inductance values. In practice both parameters can have wide variations in cables commonly used such as Rutherford cables for accelerators or Cable-in-Conduits for fusion and SMES magnets. In this paper we describe a model of a multi-stage twisted cable with arbitrary geometry that can be used to study the range of interstrand resistances and inductances that is associated with variations of geometry. These variations can be due to cabling or compaction effects. To describe the variations from the nominal geometry we have adopted a cable model that resembles to the physical process of cabling and compaction. The inductance calculation part of the model is validated by comparison to semi-analytical results, showing excellent accuracy and execution speed
Wavelet entropy and fractional Brownian motion time series
We study the functional link between the Hurst parameter and the Normalized
Total Wavelet Entropy when analyzing fractional Brownian motion (fBm) time
series--these series are synthetically generated. Both quantifiers are mainly
used to identify fractional Brownian motion processes (Fractals 12 (2004) 223).
The aim of this work is understand the differences in the information obtained
from them, if any.Comment: 10 pages, 2 figures, submitted to Physica A for considering its
publicatio
Analysis of ischaemic crisis using the informational causal entropy-complexity plane
In the present work, an ischaemic process, mainly focused on the reperfusion stage, is studied using the informational causal entropy-complexity plane. Ischaemic wall behavior under this condition was analyzed through wall thickness and ventricular pressure variations, acquired during an obstructive flow maneuver performed on left coronary arteries of surgically instrumented animals. Basically, the induction of ischaemia depends on the temporary occlusion of left circumflex coronary artery (which supplies blood to the posterior left ventricular wall) that lasts for a few seconds. Normal perfusion of the wall was then reestablished while the anterior ventricular wall remained adequately perfused during the entire maneuver. The obtained results showed that system dynamics could be effectively described by entropy-complexity loops, in both abnormally and well perfused walls. These results could contribute to making an objective indicator of the recovery heart tissues after an ischaemic process, in a way to quantify the restoration of myocardial behavior after the supply of oxygen to the ventricular wall was suppressed for a brief period.Fil: Legnani, Walter. Universidad TecnolĂłgica Nacional. Facultad Regional Buenos Aires; Argentina. Universidad Nacional de LanĂşs; ArgentinaFil: Traversaro Varela, Francisco. Instituto TecnolĂłgico de Buenos Aires; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Redelico, Francisco Oscar. Hospital Italiano; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentina. Universidad Nacional de Quilmes; ArgentinaFil: Cymberknop, Leandro Javier. Instituto Tecnologico de Buenos Aires. Departamento de Bioingenieria; Argentina. Universidad TecnolĂłgica Nacional. Facultad Regional Buenos Aires; ArgentinaFil: Armentano, Ricardo Luis. Universidad TecnolĂłgica Nacional. Facultad Regional Buenos Aires; Argentina. Instituto Tecnologico de Buenos Aires. Departamento de Bioingenieria; ArgentinaFil: Rosso, Osvaldo AnĂbal. Universidad de los Andes; Chile. Universidade Federal de Alagoas; Brasil. Hospital Italiano; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentin
The 2-Dimensional Quantum Euclidean Algebra
The algebra dual to Woronowicz's deformation of the 2-\-di\-men\-sion\-al
Euclidean group is constructed. The same algebra is obtained from
via contraction on both the group and algebra levels.Comment: 8 pages, LBL-31711 and UCB-PTH-92/0
A General Model for Thermal, Hydraulic and Electric Analysis of Superconducting Cables
In this paper we describe a generic, multi-component and multi-channel model for the analysis of superconducting cables. The aim of the model is to treat in a general and consistent manner simultaneous thermal, electric and hydraulic transients in cables. The model is devised for most general situations, but reduces in limiting cases to most common approximations without loss of efficiency. We discuss here the governing equations, and we write them in a matrix form that is well adapted to numerical treatment. We finally demonstrate the model capability by comparison with published experimental data on current distribution in a two-strand cable
Depinning of elastic manifolds
We compute roughness exponents of elastic d-dimensional manifolds in
(d+1)-dimensional embedding spaces at the depinning transition for d=1,...,4.
Our numerical method is rigorously based on a Hamiltonian formulation; it
allows to determine the critical manifold in finite samples for an arbitrary
convex elastic energy. For a harmonic elastic energy, we find values of the
roughness exponent between the one-loop and the two-loop functional
renormalization group result, in good agreement with earlier cellular automata
simulations. We find that the harmonic model is unstable with respect both to
slight stiffening and to weakening of the elastic potential. Anharmonic
corrections to the elastic energy allow us to obtain the critical exponents of
the quenched KPZ class.Comment: 4 pages, 4 figure
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