New realizations of observables in dynamical systems with second class constraints. Abstract In the Dirac bracket approach to dynamical systems with second class constrains the observables are represented by elements of a quotient Dirac bracket algebra. We describe the constraints which allow to construct families of new realizations of this algebra. The realizations are obtained as quotients o...

The twisting function describing nonstandard (super-Jordanian) quantum deformation of osp(1|2) is given in explicite closed form. The quantum coproducts and universal R-matrix are presented. The non-uniqueness of twisting function as well as two real forms of deformed osp(1|2) superalgebras are considered. One real quantum osp(1|2) superalgebra is interpreted as describing the κ-deformation of ...

New realizations of observables in dynamical systems with second class constraints. Abstract In the Dirac bracket approach to dynamical systems with second class constrains the observables are represented by elements of a quotient Dirac bracket algebra. We describe the constraints which allow to construct families of new realizations of this algebra. The realizations are obtained as quotients o...

We study dynamics of a scalar field in the near-horizon region described by a static Klein-Gordon operator which is the Hamiltonian of the system. The explicite construction of a time operator near-horizon is given and its self-adjointness discussed. ⋆ Expanded version of a poster presented at the 5 European Advanced Study Conference in Ancient Olympia, Greece, May 2004. Preprint submitted to E...

Résumé – Dans cet article, nous proposons une méthode pour l’optimisation de la métrique d’un classifieur textuel à noyaux. Contrairement aux techniques populaires existantes, notre approche ne nécessite pas la définition explicite de règles sémantiques. Etant donné un ensemble d’apprentissage, l’algorithme proposé permet d’optimiser la matrice sémantique, sans qu’il soit nécessaire d’exhiber c...

— By using the slope method, we obtain an explicit uniform estimation for the density of rational points in an arithmetic projective variety with given degree and dimension, embedded in a given arithmetic projective space. Résumé. — On obtient, en utilisant la méthode de pentes, une estimation uniforme et explicite de la densité des points rationnels dans une variété arithmétique projective de ...