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Publications FYMA
Recherchez une publication dans la base de données FYMA en
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34 publications trouvées pour ' 2003'
UCL-IPT-04-23
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Auteurs:
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Radelet-de Grave, Patricia
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Titre:
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La symétrie et l'invariance en physique et en peinture, la comparaison d'un développement
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Références:
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Turin, Mathesis 2003-2004, pp. 89-107.
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Résumé:
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UCL-IPT-04-06 : ( pdf)
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Auteurs:
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Antoine Jean-Pierre and Jacques L.
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Titre:
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The 2-D wavelet transform in image processing: Two novel applications
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Références:
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\textit{Proc. Third Int. Workshop on Contemporary Problems in Mathematical Physics (Cotonou, Bénin, Nov. 2003)}, J. Govaerts, M.N. Hounkonnou, A.Z. Msezane (eds.), World Scientific, Singapore (to appear)
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Résumé:
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UCL-IPT-04-05 : ( pdf)
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Auteurs:
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Antoine, Jean-Pierre
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Titre:
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Wavelet analysis and some of its applications in physics
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Références:
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\textit{Proc. Third Int. Workshop on Contemporary Problems in Mathematical Physics (Cotonou, Bénin, Nov. 2003)}, J. Govaerts, M.N. Hounkonnou, A.Z. Msezane (eds.), World Scientific, Singapore (to appear)
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Résumé:
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UCL-IPT-04-04 : ( pdf)
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Auteurs:
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Antoine, Jean-Pierre
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Titre:
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Partial *-algebras: General theory and some operator realizations
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Références:
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\textit{Proc. Third Int. Workshop on Contemporary Problems in Mathematical Physics (Cotonou, Bénin, Nov. 2003)}, J. Govaerts, M.N. Hounkonnou, A.Z. Msezane (eds.), World Scientific, Singapore (2004) to appear
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Résumé:
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UCL-IPT-03-17 : ( pdf)
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Auteurs:
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Calderon G., Gérard Jean-Marc, Pestieau Jean and Weyers Jacques
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Titre:
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Relating Final State Interactions in $B\rightarrow D\pi$ and $B\rightarrow DK$
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Références:
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Phys. Lett. B588 (2004) pp. 81-84
arXiv:hep-ph/0311163 v1
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Résumé:
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A Regge model calculation relates the strong phase in $B \to DK$ to that in $B\to D\pi$. This provides a significant test of a hadronic picture of final state
interactions in $B$ decays.
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UCL-IPT-03-16 : ( pdf)
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Auteurs:
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Antoine, Jean-Pierre
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Titre:
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Partial *-algebras, twenty years later
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Références:
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Suppl. Rendiconti Circolo Matematico Palermo, Ser.II, 73 (2004), pp. 13-33
(Int. Conf. Operator Theory and Operator Algebras, Altavilla
Milicia (Palermo), June 2003)
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Résumé:
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We review the main points in the development of partial *-algebras during the last 20
years, at three different levels: (i) The algebraic structure stemming from
the partial multiplication;
(ii) The locally convex *-algebras; (iii) The *-algebras of closable operators in
Hilbert spaces or partial *-algebras, including the representation theory of the abstract *-algebras.
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UCL-IPT-03-15 : ( pdf)
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Auteurs:
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C. Smith
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Titre:
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Searching for dominant rescattering sources in B to two pseudoscalar decays
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Références:
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hep-ph/0309062
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Résumé:
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Various rescattering sources are analyzed in the context of the SU(3) flavor symmetry. In particular, the possibility to account for intermediate charm at the hadronic level in B to PP is thoroughly investigated. Then, the rescattering sources are compared in light of recent B to two charmless pseudoscalar decay measurements, with emphasis on the size of strong phases and on patterns of direct CP-asymmetries.
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UCL-IPT-03-13 : ( pdf)
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Auteurs:
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S. Trine
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Titre:
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Strong anomalies in kaon decays
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Références:
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hep-ph/0305048
Talk presented at the 38th Rencontres de Moriond on Electroweak Interactions and Unified Theories, Les Arcs, France, March 15-22, 2003. To appear in the proceedings
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Résumé:
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We point to a potentially large contribution of the QCD trace anomaly to the isoscalar pion pair production in Kaon decays. This contribution arises from the long-distance evolution of a 7-dimensional quark-gluon operator generated by short-distance QCD corrections to the $\Delta_S=1$ Fermi Hamiltonian.
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UCL-IPT-03-12 : ( pdf)
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Auteurs:
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Jean-Pierre Antoine, L. Jacques
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Titre:
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Angular multiselectivity analysis of images
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Références:
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Wavelets Applications in Signal and Image Processing X, Proc. SPIE, vol. 5207 (2003) pp. 196-207
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Résumé:
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Two-dimensional wavelet analysis with directional frames is
well--adapted and efficient for
detecting oriented features in images but, for (quasi-)isotropic
components, it is unnecessarily redundant. Using wavelets with variable angular selectivity leads to a prohibitive computing cost in the continuous wavelet formalism. We propose here a solution based on a multiresolution analysis in the angular variable (transferred from a biorthogonal analysis on the line), in addition to the usual multiresolution in scale. The resulting scheme is efficient and competitive with traditional methods. Some applications are given to image denoising.
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UCL-IPT-03-11 : ( pdf)
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Auteurs:
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C. Smith
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Titre:
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What could be learnt from Positronium for Quarkonium?
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Références:
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12 pages, 10 figures. Talk given at the ETH Workshop on
Positronium Physics, May 30-31, 2003, Zurich, Switzerland
hep-ph/0308082
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Résumé:
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In order to fulfill Low's theorem requirements, a new lowest order basis for
bound state decay computations is proposed, in which the binding energy is
treated non-perturbatively. The properties of the method are sketched by
reviewing standard positronium decay processes. Then, it is shown how
applying the method to quarkonia sheds new light on some longstanding
puzzles.
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UCL-IPT-03-10 : ( pdf)
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Auteurs:
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S. Gissot, J-F. Hochedez, F. Dibos, R. Brajsa, L. Jacques, D. Berghmans, A. Zhukov, F. Clette, H. Wöhl, Jean-Pierre Antoine
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Titre:
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Extracting the apparent motion from two successive EIT images
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Références:
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Proc. Conf. ISCS2003 (July 2003, Tatranska Lomnica, Slovak Republic). (to appear) (2003)
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Résumé:
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The EIT observations cover more than seven years of the 23rd solar cycle. The main synoptic dataset,
usually refered to as the 'CME Watch', is a nearly uninterrupted sequence of images taken in the Fe XII bandpass at a cadence of four images per hour. In this work we study motion tracking methods in order to estimate displacements from frame to frame. We have implemented a novel optical
ow algorithm, and tested it on a couple of successive images. We
have linked the apparent motion occuring between two frames to the expected rotation rate. On this
short time scale (20 minutes), we are able to retrieve the global parameters of the solar differential rotation. A strategy for the extraction of region with
reliable motion will be discussed.
Keywords: EIT; differential rotation; motion analysis; optical flow.
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UCL-IPT-03-09 : ( pdf)
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Auteurs:
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Branco G.C., Gérard Jean-Marc, Gonzalez Felipe R. and Nobre B.M.
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Titre:
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Polychromatic Grand Unification
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Références:
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arXiv:hep-ph/0305092 v1
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Résumé:
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The possibility of achieving a gauge coupling grand unification by increasing the QCD degrees of freedom at higher energies is investigated. When confronted with precision low-energy data, the generic weak-mixing angle relation $\sin^2 \theta_W = N/2(N+1)$ requires N=7 colors at the GUT scale $M_U \simeq 10^{17}$ GeV. With the exclusive addition of light Higgs doublets to the standard model particle content, such a unification may also occur if $N=5$ at $M_U \simeq 10^{16}$ GeV.
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UCL-IPT-03-08 : ( pdf)
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Auteurs:
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Lefevere R., Schenkel A.
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Titre:
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Perturbative analysis of anharmonic chains of oscillators out of equilibrium
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Références:
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Submitted to Journal of Statistical Physics
math-ph/0303050
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Résumé:
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We compute the first-order correction to the correlation functions of the stationary state of a stochastically forced harmonic chain out of equilibrium when a small on-site anharmonic potential is added. This is achieved by
deriving a suitable formula for the covariance matrix of the invariant state.
We find that the first-order correction of the heat current does not depend on the size of the system. Second, the temperature profile is linear when the
harmonic part of the on-site potential is zero. The sign of the gradient of the profile, however, is opposite to the sign of the temperature di_erence of the
two heat baths.
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UCL-IPT-03-07 : ( pdf)
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Auteurs:
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A.L. Hohoueto, K. Thirulogasanthar, S.T. Ali, Jean-Pierre Antoine
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Titre:
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Coherent states lattices and square integrability of representations.
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Références:
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Journal of Physics A : Math. Gen. 36 (2003) pp. 11817-11835
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Résumé:
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In this paper, we discretize the continuous theory of coherent states on a general semidirect
product group $G=V\rtimes S$, where $V$ is a vector space and $S
\subset GL(V)$ is a semisimple
connected Lie group. We show that it is always possible to construct
a discrete frame associated to a UIR of $G$, which is square integrable modulo an affine admissible section. We also prove the converse result that the existence of a discrete frame associated to a unitary
representation $U$ of $G$, indexed by a homogeneous space $\G$, implies the square integrability of $U$ on $\G$
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UCL-IPT-03-06 : ( pdf)
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Auteurs:
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J-F. Hochedez, S. Gissot, L. Jacques, Jean-Pierre Antoine
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Titre:
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Multiscale observations of the Solar atmosphere
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Références:
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GROUP 24: Physical and Mathematical Aspects of Symmetries. pp. 931-936; J-P. Gazeau, R. Kerner, J-P. Antoine, S. Metens, J-Y. Thibon (eds.), Inst. Phys. Conf. Series, vol. 173, IOP Publishing, Bristol, 2003
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Résumé:
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The observations of the Extreme ultraviolet Imaging Telescope (EIT)
contain various small features of the solar coronal regions: EUV, bright points, ephemeral regions,
brightenings, loops segments, cosmic ray hits, etc. In this work we present an automated method for extracting small objects. It is based on the continuous 2D Mexican Hat Wavelet transform. We study global and long-term statistical
properties of the small features. Their distribution will be used for solar cycle studies and prediction of solar events (Space Weather applications).
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UCL-IPT-03-05 : ( pdf)
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Auteurs:
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Jean-Pierre Antoine, L. Jacques
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Titre:
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Measuring a curvature radius with directional wavelets
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Références:
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GROUP 24: Physical and Mathematical Aspects of Symmetries. pp. 899-904; J-P. Gazeau, R. Kerner, J-P. Antoine, S. Metens, J-Y. Thibon (eds.), Inst. Phys. Conf. Series, vol. 173, IOP Publishing, Bristol, 2003
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Résumé:
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We present in this paper a new technique based on the Continuous
Wavelet Transfrom (CWT) for estimating the curvature radius of contours delimiting simple objects in images. This method exploits the link which exists between the angular response of directional wavelets and the curvature radius of the analyzed curves.
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UCL-IPT-03-04 : ( pdf)
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Auteurs:
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A.L. Hohoueto, T. Kengaratham, S.T. Ali, Jean-Pierre Antoine
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Titre:
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Lattices of coherent states and square integrability
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Références:
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GROUP 24: Physical and Mathematical Aspects of Symmetries. pp. 883-886; J-P. Gazeau, R. Kerner, J-P. Antoine, S. Metens, J-Y. Thibon (eds.), Inst. Phys. Conf. Series, vol. 173, IOP Publishing, Bristol, 2003
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Résumé:
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We develop a method of discretization of the continuous theory of coherent states on a general semidirect product Lie group. The group is assumed to have a unitary representation which is
square integrable on some homogeneous space. We show also that the existence of a discrete frame of coherent states in the carrier space of a unitary representation of such a group implies the square integrability of this representation on the label space.
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UCL-IPT-03-02 : ( pdf)
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Auteurs:
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Jean Pestieau
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Titre:
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A remarkable relation in the gauge sector of electroweak dynamics
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Références:
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X Mexican School on Particles and Fields, Playa del Carmen, Mexico (2002)
hep-ph/0301139
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Résumé:
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A precise empirical relation between the electromagnetic coupling $\alpha(m_Z)$ and $\sin^2 (\theta^ell_{eff})$ --where $\theta^ell_{eff}$ is the effective electroweak mixing angle extracted from Z leptonic decays-- is made manifest: $\alpha(m_Z)$ =
$\sin^3 (\theta^ell_{eff})* \cos(\theta^\ell_{eff}}/(4\pi}$.
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UCL-IPT-03-01 : ( pdf)
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Auteurs:
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Gérard Jean-Marc and Smith C.
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Titre:
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Are $B \to \pi K$ CP-asymmetries quantized ?
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Références:
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Eur.Phys.J. C30 (2003) 69
hep-ph/0301180
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Résumé:
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Search for patterns in the numerous B-decay modes now available is necessary in order to test the Cabibbo-Kobayashi-Maskawa theory of CP-violation. In particular, the well-structured pattern of B to PI K branching ratios may lead to a quantized spectrum for direct CP-asymmetries, providing in this way a rather unique opportunity to discriminate between strong final state interaction models.
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UCL-IPT-02-16 : ( pdf)
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Auteurs:
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Bricmont, Jean
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Titre:
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Determinism, Chaos and Quantum Mechanics
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Références:
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Preprint
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Résumé:
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After some general remarks on the notion of 'determinism', I will discuss the precise meaning of chaos theory and the frequent misunderstandings concerning the implications of that theory. After reviewing the status of probabilistic reasoning in classical physics, I will also briefly discuss misunderstandings occurring in the context of quantum mechanics.
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UCL-IPT-02-15 : ( ps.gz)
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Auteurs:
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C. Smith
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Titre:
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Very Low Energy Matching of Effective Meson Theories with QCD
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Références:
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hep-ph/0207284, submitted
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Résumé:
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A simple matching procedure is proposed to extract constraints on effective meson theories. In this way, a QCD prediction for the pion decay constant is found, F_\pi = 2m_\pi/\pi \approx 90 MeV. The same procedure also determines other mesonic observables, like the decay width of the sigma meson to two photons.
Finally, some information which can be gained about the hadronic light-by-light contributions to the muon anomalous moment are briefly commented.
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UCL-IPT-02-12 : ( pdf)
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Auteurs:
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Escribano R., Gallegos A., Lucio M. J.L., Moreno G., Pestieau Jean
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Titre:
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On the mass, width and coupling constants of the f_0(980)
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Références:
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UAB-FT-524
April 2002
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Résumé:
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Using the pole approachwedetermine the mass and width of the
$f_0$(980), in particular we analyze the possibility that two nearbypoles
are associated to it. We restrict our analysis to a neighborhood of
the resonance, using $\pi\pi$ data for the phase shift and inelasticity, and
the invariant mass spectrum of the $J/\psi \to \phi\pi\pi, \phi K\bar K$ decays. The formalism weuse is based on unitarity and a generalized version of the Breit Wigner parameterization. We find that a single pole describes the $f_0$(980) leading to $m_{f_0}$ = 999$\pm$2 MeV ($m_{f_0}$ = 987$\pm$3 MeV) and $\Gamma_{f_0}$=39$\pm$8 MeV ($\Gamma_{f_0}=42$\pm$9 MeV) depending upon the $\pi\pi$
phase shift data used. As a byproduct values for the $g_{f_0\pi\pi}$ and $g_{f_0 K \bar K}$ coupling constants are obtained.
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UCL-IPT-02-09
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Auteurs:
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Radelet-de Grave Patricia
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Titre:
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L'univers selon Huygens, le connu et l'imaginé
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Références:
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'Expérience et raison, la science chez Huygens (1629-1695)', Revue d'Histoire des Sciences, Tome 56-1, Paris, PUF (2003) pp. 79-112
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Résumé:
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UCL-IPT-02-06
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Auteurs:
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Radelet-de Grave Patricia
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Titre:
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The use of a particular form of the parallelogram law of forces for the building of vaults (1650-1750)
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Références:
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Essays on the History of Mechanics. In Memory of Clifford Ambrose Truesdell and Edoardo Benvenuto. Eds. Antonio Becchi, Massimo Corradi, Federico Foce, Orietta Pedemonte. http://www.birkhauser.com/detail.tpl?isbn=3764314761
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Résumé:
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UCL-IPT-01-15 : ( pdf)
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Auteurs:
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S. Pireaux, J-P. Rozelot
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Titre:
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Solar quadrupole moment and purely relativistic gravitation contributions to Mercury's perihelion Advance
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Références:
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Astrophysics and Space Science 284: (2003) 1159-1194
astro-ph/0109032
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Résumé:
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The perihelion advance of the orbit of Mercury has long been one of the observational cornerstones for testing General Relativity (G.R.).
The main goal of this paper is to discuss how, presently, observational and theoretical constraints may challenge Einstein's theory of gravitation characterized by beta=gamma=1. To achieve this purpose, we will first recall the experimental constraints upon the Eddington-Roertson parameters gamma,beta and the observational bounds for the perihelion advance of Mercury Delta omega_{obs}.
A second point will address the values given, up to now, to the solar quadrupole moment by several authors. Then, we will briefly comment why we use a recent theoretical determination of the solar quadrupole moment, J2=(2.0+/-0.4)10^{-7}, which takes into account both surfacic and internal differential rotation, in order to compute the solar contribution to Mercury's perihelion advance.
Further on, combining bounds on gamma and J2 contributions, and taking into account the observational data range for Delta omega_{obs}, we will be able to give a range of values for beta.
Alternatively, taking into account the observed value of Delta omega_{obs}, one can deduce a dynamical estimation of J2 in the setting of G.R. This point is important as it provides a solar model independent estimation that can be confronted with other determinations of J2 based upon solar theory and solar observations (oscillation data, oblateness...).
Finally, a glimpse at future satellite experiments will help us to understand how stronger constraints upon the parameter space (gamma,beta,J2) as well as a separation of the two contributions (from the quadrupole moment, J2, or purely relativistic, 2 alpha^2 + 2 alpha gamma - beta) might be expected in the future.
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UCL-IPT-01-05
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Auteurs:
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Jean-Pierre Antoine
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Titre:
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Continuous wavelets on the 2-sphere
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Références:
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Revista Ciencias Matematicas (La Habana) 19 (2003) pp. 22-38
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Résumé:
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We present a group-theoretical derivation of the continuous wavelet transform (CWT) on the 2-sphere $S^2$, based on the construction of coherent states associated to
square integrable group representations. The parameter space $X$ is the product of $SO(3) \cdot\R_*^+$, embedded into
the Lorentz group $SO_o(3,1)$ via the Iwasawa decomposition, and $X \simeq SO_o(3,1)/\C$. The space $L^2(S^2,d\mu)$ carries a unitary irreducible representation of
$SO_o(3,1)$, which is square integrable over $X$, and thus yields the wavelets on $S^2$ and the associated CWT. We briefly discuss the numerical implementation of the latter. Finally, we derive a reconstruction formula valid in strong $L^2$ sense, which leads to the approximation of functions on the sphere using an approximate
identity, obtained by a suitable dilation of the mother wavelet.
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UCL-IPT-01-04
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Auteurs:
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Jean-Pierre Antoine
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Titre:
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Discrete wavelets on abelian locally compact groups
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Références:
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Revista Ciencias Matematicas (La Habana) 19 (2003), pp. 3-21
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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 ${\mathcal A}\rtimes\Gamma$ on $\ell^2(\Gamma)$, where
$\Gamma$ is a lattice
and ${\mathcal A}$ 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-01-02
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Auteurs:
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Ngakeu F., Lambert D., Ezin J-P.
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Titre:
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On some Sweedler-Hopf algebras and their noncommutative geometry
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Références:
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Journal of Mathematical Physics (2003) soumis
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Résumé:
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A sequence (A_N) of finite dimensional Hopf algebras is defined, it turns out that the dual A^*_N of any A_N (which is a generalized Sweedler algebra) is a quasitriangular Hopf algebra from which we derive some families of matrices that are solutions of Yang-Baxter equations. We introduce some constructions of noncommutative geometry on both A^*_N and its Drinfeld quantum double D(A^*_N), including bicovariant differnetial calculi and quantum principal bundle structures according to Brzezinski and Majid.
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UCL-IPT-01-01
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Auteurs:
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Jean-Pierre Antoine, L. Hohoueto
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Titre:
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Discrete frames of Poincaré coherent states in 1+3 dimensions
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Références:
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J. of Fourier Analysis and Applications 9 (2003) pp. 141-173
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Résumé:
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Continuous frames of coherent states of the Poincar\'e group in 1+3
dimensions $\Pgg$ have been obtained previously. We address in this paper
the problem of discretizing (sampling) such continuous frames. The discrete frames constructed here are sets of coherent states built from compactly supported functions and the Wigner representation of the group for mass $m>0$ and spin $s \in \N/2$. We examine three specific examples in detail and show that tight frames may be obtained, under particular conditions, in the case of the Lorentz section
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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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(Jules) Arthur Vierendeel
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Références:
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Erfinder des Trägers ohne Diagonalen, Deutsche Bauzeitung, 137. Jahrg. 08/2003 (2003) pp. 84-87.
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Résumé:
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UCL-IPT-
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Auteurs:
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Radelet-de Grave Patricia and Van Tiggelen B. (Eds.)
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Titre:
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Sedes scientiae, l'émergence de la recherche à l'Université, Réminisciences, 6, Brepols, 2003.
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Références:
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Résumé:
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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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Les Jésuites, l'Université de Louvain et les recherches en physique, dans P. Radelet-de Grave, B. Van Tiggelen (Eds.), Sedes scientiae, l'émergence de la recherche à l'Université, Réminisciences, 6, Brepols (2003) pp. 72-125.
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Références:
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Résumé:
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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-
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Auteurs:
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Radelet-de Grave, Patricia
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Titre:
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it{La caténaire ou comment le calcul différentiel fait son apparition sur la place publique},
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Références:
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dans it{L’histoire des sciences en fait et en actes}, Sciences et Techniques en perspective, deuxième série, vol. 7 – Nr 1 – 2003, pp. 91-116.
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Résumé:
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