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Publications FYMA
Recherchez une publication dans la base de données FYMA en
entrant des mots clés (auteurs, année, titre, ...) dans la case suivante:
21 publications trouvées pour ' 2000'
UCL-IPT-00-26
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Auteurs:
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Radelet-de Grave, Patricia
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Titre:
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Le beau est la splendeur du vrai
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Références:
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Aventure universitaire, Livre commémoratif des 575 ans de l'Université catholique de Louvain, Edition Racine (2000) p. 151
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Résumé:
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UCL-IPT-00-25 : ( pdf)
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Auteurs:
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Radelet-de Grave, Patricia
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Titre:
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Influencia de los vortices magnéticos sobre la idea cartesiana de los vortices planetarios
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Références:
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in Descartes : y la ciencia del siglo XVII. Ciencia y Técnica (2000) 272-290
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Résumé:
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UCL-IPT-00-24
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Auteurs:
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Radelet-de Grave, Patricia
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Titre:
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Article : Minkowski
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Références:
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Dictionnaire du patrimoine littéraire européen, Patrimoine Littéraire Européen, vol. 12 (2000) pp. 333-341, De Boeck Université, Louvain-la-Neuve
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Résumé:
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UCL-IPT-00-20 : ( ps.gz)
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Auteurs:
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Gérard, Jean-Marc
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Titre:
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De l'éclipse totale du soleil au problème de la constante cosmologique
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Références:
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Physcialia Mag. 22 (2000) 3-25
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Résumé:
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Recent observations that early stellar explosions look dimmer than
expected suggest that the expansion of our Universe may be speeding up rather than slowing down. The argument for cosmic acceleration fueled by a cosmological constant
depends on two key measurements: the maximum brightness of the explosion which shows when it took place, and its spectral redshift which records how much the Universe has expanded since it occured. It is probably premature to present the accelerating Universe as the new revolution in cosmology. So, here we mainly focus on the orders of magnitude involved in such a new promising area of astroparticle
physics.
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UCL-IPT-00-14
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Auteurs:
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Stéphanie Trine
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Titre:
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Analysis of B-meson decays into two light pseudoscalars
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Références:
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Physicalia Magazine 22 (2000) 163-172
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Résumé:
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UCL-IPT-00-13 : ( ps.gz)
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Auteurs:
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Mikael Beuthe
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Titre:
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La quête d'une nouvelle théorie de la gravitation (Le pourquoi
des équations de la relativité générale)
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Références:
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non publié Cours (2000) in French, 157 pages, 31 figures
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Résumé:
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Ce cours vise à expliquer aux débutants les équations de la
relativité générale, sans en couvrir les vastes champs
d'application (trous noirs, ondes gravitationnelles et
cosmologie). L'équation des géodésiques et l'équation d'Einstein
sont dérivées, en grand détail, à partir du Principe d'Equivalence
et du Principe de Covariance Générale (le Principe Variationnel
n'est pas utilisé car il est trop limitatif). Le recours à de
nouveaux concepts mathématiques est minimisé (approche non
géométrique).
Mots-clés : gravitation, relativité générale, principe d'équivalence.
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UCL-IPT-00-12 : ( ps.gz)
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Auteurs:
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Mikael Beuthe
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Titre:
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Propagation et oscillations en théorie des champs
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Références:
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non publié Thèse de doctorat en Sciences UCL (2000)
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Résumé:
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After a review of the problems associated with the conventional
treatment of particle oscillations, an oscillation formula is
derived within the framework of quantum field theory. The
oscillating particle is represented by its propagator and the
initial and final states by wave packets. It is obviously
relativistic from the start and moreover applies both to stable
(neutrinos) and unstable particles (K and B mesons, unstable
neutrinos). CPLEAR and DAFNE experiments are studied as examples,
with special attention directed to CP violation. The problems
resulting from equal energies/momentum/velocities prescriptions
are analyzed and solved. Oscillations of associated particles are
found to be nonexistent. The relativistic generalization of the
Wigner-Weisskopf equation is also derived.
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UCL-IPT-00-11
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Auteurs:
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G. Menegaz, A. Rivoldini and J-Ph. Thiran
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Titre:
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Dyadic frames of directional wavelets as texture descriptors
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Références:
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à paraître Wavelets Applications in Signal and Image
Processing VIII vol. 4119 (2000) pp. 263-273
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Résumé:
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UCL-IPT-00-03 : ( ps.gz)
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Auteurs:
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Jean-Pierre Antoine
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Titre:
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Two-dimensional directional wavelets as a symmetry scanner
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Références:
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Contemporary Problems in Mathematical Physics (Proc. First
Int.Workshop, Cotonou, Bénin, Nov.1999), 2000, pp.47-60, J.Govaerts, M.N.Hounkonnou, W.A.Lester, Jr. (eds.)
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Résumé:
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The analysis of oriented features in images requires 2-D
directional wavelets, for instance, in standard tasks such as edge
detection or directional filtering. In addition, we present here a
new application, namely, a technique for determining all the
(statistical) symmetries of a given pattern with respect to
rotations and dilations. Examples are Penrose tilings,
mathematical quasicrystals or various quasiperiodic planar point
sets or patterns.
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UCL-IPT-00-02 : ( ps.gz)
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Auteurs:
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Jean-Pierre Antoine
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Titre:
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Coherent states, wavelets and beyond
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Références:
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Contemporary Problems in Mathematical Physics (Proc. First
Int.Workshop, Cotonou, Bénin, Nov.1999), 2000, pp.3-46, J.Govaerts, M.N.Hounkonnou, W.A.Lester, Jr. (eds.)
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Résumé:
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The first lecture describes classical coherent states (CS),
starting from the (canonical) harmonic oscillator CS, and
proceeding to the theory of Gilmore and Perelomov, who derive
CS from suitable (square integrable) group representations.
The second lecture is devoted to a highly successful example,
namely wavelets, which are simply the CS of the affine group
of the line (dilations and translations) or the similitude
group of the plane, for the 2-D case. In the third lecture,
we conclude with a far-reaching generalization of the
classical theory, namely CS associated with a group
representation which is square integrable only over a
homogeneous manifold of the group. This case, while
technically more involved, covers a whole family of groups
inaccessible to the standard Gilmore--Perelomov approach, and
among them, in particular, the relativity groups.
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UCL-IPT-00-01 : ( ps.gz)
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Auteurs:
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A. Coste, T. Gannon and Philippe Ruelle
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Titre:
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Finite Group Modular Data
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Références:
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Nuclear Physics B581 (2000) 679-717
hep-th/0001158
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Résumé:
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The modular data associated to finite groups is remarkably
ubiquitous. And yet, compared to the well-understood affine
algebra modular data, the general properties of this finite group
modular data has been poorly explored. In this paper we undergo
such a study. We identify some senses in which the finite group
data is similar to, and different from, the affine data. We also
consider the data arising from a cohomological twist, and write
down, explicitly in terms of quantities associated directly with
the finite group, the modular $S$ and $T$ matrices for a {it
general} twist, for what appears to be the first time in print.
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UCL-IPT-
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Auteurs:
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Radelet-de Grave Patricia
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Titre:
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Historiographie de la mécanique de 1975 à 2000, une étude statistique
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Références:
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LULL, vol. 26 (2003) pp. 995-1044.
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Résumé:
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UCL-IPT-99-15 : ( ps.gz)
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Auteurs:
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Jean Bricmont, A. Kupiainen and R. Lefevere
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Titre:
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Probabilistic estimates for the two-dimensional stochastic Navier-Stokes equation
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Références:
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Journal of Statistical Physics, 100, nrs. 3/4, (2000) pp. 743-756
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Résumé:
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We consider the Navier-Stokes equation on a two-dimensional torus with a random force, white noise in time, and analytic in space, for arbitrary Reynolds number $R$. We prove probabilistic estimates for the long-time behavior of the solutions that imply bounds for the dissipation scale and energy spectrum as $R to infty$.
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UCL-IPT-99-14 : ( ps.gz)
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Auteurs:
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Jean-Pierre Antoine
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Titre:
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Wavelet analysis of signals and images: A grand tour
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Références:
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Revista Ciencias Matematicas (La Habana) 18 (2000) pp. 113-143
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Résumé:
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We review the general properties of the wavelet transform, both in its
continuous and its discrete versions, in one or two dimensions, and we describe some of its applications in signal and image processing. We also consider its extension to higher dimensions and to the space-time context, for the analysis of moving objects.
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UCL-IPT-99-07
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Auteurs:
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S. Twareque Ali, Jean-Pierre Antoine, J.-P. Gazeau
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Titre:
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Coherent States, Wavelets and their Generalizations
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Références:
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a volume of xvi + 418 pages (hc) Graduate Texts in Contemporary Physics Springer-Verlag, New York, Berlin, Heidelberg, 2000 ISBN 0-387-98908-0
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Résumé:
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UCL-IPT-99-03 : ( ps.gz)
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Auteurs:
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Jean-Pierre Antoine, A. Coron, J.-M. Dereppe
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Titre:
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Water Peak Suppression : Time-Frequency emph{vs} Time-Scale
Approach
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Références:
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Journal of Magnetic Resonance 144(2) (2000) 189-194
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Résumé:
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Wavelets are the most popular time-scale analysis tool. A well known application of wavelets in Nuclear Magnetic Resonance Spectroscopy is water peak extraction/suppression. However spectroscopists are more familiar with frequency than scale. So, from a spectroscopist point of view, a time-scale analysis tool (i.e. wavelets) is not natural and a time-frequency approach would be much more satisfactory. We explain a time-frequency solution to this problem based on Gabor analysis. As the two formalisms are closely linked together we continuously emphasize their similarities and differences. In particular we show that, here, the Gabor method is as efficient as the wavelet approach, and give some examples.
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UCL-IPT-99-01 : ( ps.gz)
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Auteurs:
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Jean-Pierre Antoine, A. Inoue, H. Ogi
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Titre:
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Standard generalized vectors and *-automorphism groups of partial O*-algebras
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Références:
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Reports on Mathematical Physics 45 (2000) pp. 39-66
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Résumé:
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It is known that standard generalized vectors on a partial O*-algebra M provide a way of constructing (generalized) KMS states on M, via the Tomita-Takesaki theory of modular automorphisms. Such states would represent equilibrium states if M is the observable set of some physical system. In this paper we discuss a simplified form of these standard generalized vectors, called natural, characterized by the fact that they have a core consisting of universal right multipliers. We also investigate the interplay between the *-automorphism groups generated by two standard generalized vectors $lambda$ and $mu$ on M. When M is a self-adjoint partial GW*-algebra, we prove the existence of the Connes cocycle $[Dmu:Dlambda]$ and we establish a Radon-Nikodym theorem, generalizing that obtained by Pedersen and Takesaki for a von Neumann algebra.
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UCL-IPT-98-20
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Auteurs:
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Jean-Pierre Antoine
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Titre:
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Partial *-algebras: A retrospective
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Références:
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(Proc. 12th Max Born Symposium, Wroclaw, September 1998), B. Jancewicz and W. Karwowski (eds.); Lecture Notes in Physics, vol. 539, pp. 161-179, Springer-Verlag, Berlin, (2000)
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Résumé:
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We review the main points in the development of pa s during the last 15 years, at three different levels. (i) The algebraic structure stemming from the partial multiplication; (ii) The topological pa s; (iii) The pa s of closable operators in Hilbert spaces or po s, including the representation theory of the abstract pa s.
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UCL-IPT-98-18 : ( ps.gz)
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Auteurs:
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Jean-Pierre Antoine, Y. B. Kouagou, D. Lambert, B. Torrésani
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Titre:
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An algebraic approach to discrete dilations. Application to discrete wavelet transforms
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Références:
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J. of Fourier Analysis and Applications 6 (2000) pp. 113-141
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Résumé:
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We investigate the connections between continuous and discrete wavelet transforms on the basis of algebraic arguments. The discrete approach is formulated abstractly in terms of the action of a semidirect product $cA imesGamma$ on $ell^2(Gamma)$, with $Gamma$ a lattice and $cA$ an abelian semigroup acting on $Gamma$. We show that several such actions may be considered, and investigate those which may be written as deformations of the canonical one. The corresponding deformed dilations (the pseudodilations) turn out to be characterized by compatibility relations of a cohomological nature. The connection with multiresolution wavelet analysis is based on families of pseudodilations of a different type.
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UCL-IPT-98-11 : ( ps.gz)
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Auteurs:
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Jean-Pierre Antoine, A. Inoue, C. Trapani
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Titre:
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Biweights on partial *-algebras
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Références:
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Journal of Mathematical Analysis and Applications 242 (2000) pp. 164-190
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Résumé:
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Represenatations of *-algebras are generally obtained by the familiar Gelfand-Naimark-Segal (GNS) construction, starting from a positive linear functional, or even a (quasi-)weight, that is a functional that may take infinite values. In previous works, we have extended this construction to the case of a partial *-algebra, using invariant positive sesquilinear forms, which play the same role as positive linear functionals for *-algebras. In this paper we extend the construction further, by introducing and studying systematically the notion of biweight on a partial *-algebra. In particular, we characterize, through the associated GNS representation, the so-called approximately admissible biweights (i.e. limits of biweights with a bounded GNS representation).
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UCL-IPT-98-07
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Auteurs:
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H. Drissi, F. Regragui, Jean-Pierre Antoine, M. Bennouna
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Titre:
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Wavelet transform analysis of visual evoked potentials: some preliminary results.
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Références:
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ITBM-RBM (Innovation et Technologie en Biologie et Médecine) 21, pp. 84-91 (2000)
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Résumé:
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Visual Evoked Potentials are analyzed with the continuous wavelet transform. The method yields a fine spectral analysis of the data and allows a clearcut discrimination between normal persons and pathological cases.
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