940 research outputs found
Generalized probabilities in statistical theories
In this review article we present different formal frameworks for the
description of generalized probabilities in statistical theories. We discuss
the particular cases of probabilities appearing in classical and quantum
mechanics, possible generalizations of the approaches of A. N. Kolmogorov and
R. T. Cox to non-commutative models, and the approach to generalized
probabilities based on convex sets
Deterministic ratchet from stationary light fields
Ratchets are dynamic systems where particle transport is induced by
zero-average forces due to the interplay between nonlinearity and asymmetry.
Generally, they rely on the effect of a strong external driving. We show that
stationary optical lattices can be designed to generate particle flow in one
direction while requiring neither noise nor driving. Such optical fields must
be arranged to yield a combination of conservative (dipole) and nonconservative
(radiation pressure) forces. Under strong friction all paths converge to a
discrete set of limit periodic trajectories flowing in the same direction.Comment: 6 pages, 4 figure
Electromagnetic surface states in structured perfect-conductor surfaces
Surface-bound modes in metamaterials forged by drilling periodic hole arrays
in perfect-conductor surfaces are investigated by means of both analytical
techniques and rigorous numerical solution of Maxwell's equations. It is shown
that these metamaterials cannot be described in general by local,
frequency-dependent permittivities and permeabilities for small periods
compared to the wavelength, except in certain limiting cases that are discussed
in detail. New related metamaterials are shown to exhibit exciting optical
properties that are elucidated in the light of our simple analytical approach.Comment: 5 figure
On the density of states and extinction mean free path of waves in random media: Dispersion relations and sum rules
We establish a fundamental relationship between the averaged density of
states and the extinction mean free path of wave propagating in random media.
From the principle of causality and the Kramers-Kronig relations, we show
that both quantities are connected by dispersion relations and are constrained
by a frequency sum rule. The results are valid under very general conditions
and should be helpful in the analysis of measurements of wave transport through
complex systems and in the design of randomly or periodically structured
materials with specific transport properties.Comment: 2 (double) figures, 8 page
Full transmission through perfect-conductor subwavelength hole arrays
Light transmission through 2D subwavelength hole arrays in perfect-conductor
films is shown to be complete (100%) at some resonant wavelengths even for
arbitrarily narrow holes. Conversely, the reflection on a 2D planar array of
non-absorbing scatterers is shown to be complete at some wavelengths regardless
how weak the scatterers are. These results are proven analytically and
corroborated by rigorous numerical solution of Maxwell's equations. This work
supports the central role played by dynamical diffraction during light
transmission through subwavelength hole arrays and it provides a systematics to
analyze more complex geometries and many of the features observed in connection
with transmission through hole arrays.Comment: 5 pages, 4 figure
TOY: A System for Experimenting with Cooperation of Constraint Domains
AbstractThis paper presents, from a user point-of-view, the mechanism of cooperation between constraint domains that is currently part of the system TOY, an implementation of a constraint functional logic programming scheme. This implementation follows a cooperative goal solving calculus based on lazy narrowing. It manages the invocation of solvers for each domain, and projection operations for converting constraints into mate domains via mediatorial constraints. We implemented the cooperation among Herbrand, real arithmetic (R), finite domain (FD) and set (S) domains. We provide two mediatorial constraints: The first one relates the numeric domains FD and R, and the second one relates FD and S
La competición en la iniciación al baloncesto
Las situaciones de competición deportiva en general, y del baloncesto en particular, van a ser claves en el aprendizaje correcto de un deporte. Estas situaciones de competición no solo van a ser un factor de motivación importantÃsimo, sino que además van a asegurarnos la práctica constante de situaciones reales de juego. Las competiciones oficiales que se realizan en la actualidad no van a asegurar un desarrollo motriz adecuado. Utilizan reglas demasiado rÃgidas, material inadecuado, poca participación, situaciones de juego complicadas, etc. En el presente artÃculo vamos a exponer algunas situaciones de competición que creemos adecuadas. Estas situaciones van a evolucionar en intensidad y dificultad dependiendo de la edad y del nivel de los jugadores/as. Cada propuesta va a cambiar, en relación con el reglamento oficial, las situaciones de juego, las medidas del campo, la altura del aro, el balón y algunas reglas. Por lo tanto, la competición que vamos a plantear va a tener una serie de caracterÃsticas tanto educativas como metodológicas, adaptadas a las diferentes etapas de formación de nuestros alumnos
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