Scattering of cosmic strings by black holes: loop formation

We study the deformation of a long cosmic string by a nearby rotating black hole. We examine whether the deformation of a cosmic string, induced by the gravitational field of a Kerr black hole, may lead to the formation of a loop of cosmic string. The segment of the string which enters the ergosphere of a rotating black hole gets deformed and, if it is sufficiently twisted, it can self-intersect chopping off a loop of cosmic string. We find that the formation of a loop, via this mechanism, is a rare event. It will only arise in a small region of the collision phase space, which depends on the string velocity, the impact parameter and the black hole angular momentum. We conclude that generically, the cosmic string is simply scattered or captured by the rotating black hole.Comment: 11 pages, 2 figures, RevTe

D-term inflation in non-minimal supergravity

D-term inflation is one of the most interesting and versatile models of inflation. It is possible to implement naturally D-term inflation within high energy physics, as for example SUSY GUTs, SUGRA, or string theories. D-term inflation avoids the $\eta$-problem, while in its standard form it always ends with the formation of cosmic strings. Given the recent three-year WMAP data on the cosmic microwave background temperature anisotropies, we examine whether D-term inflation can be successfully implemented in non-minimal supergravity theories. We show that for all our choices of K\"ahler potential, there exists a parameter space for which the predictions of D-term inflation are in agreement with the measurements. The cosmic string contribution on the measured temperature anisotropies is always dominant, unless the superpotential coupling constant is fine tuned; a result already obtained for D-term inflation within minimal supergravity. In conclusion, cosmic strings and their r\^ole in the angular power spectrum cannot be easily hidden by just considering a non-flat K\"ahler geometry.Comment: 29 pages, 9 figures; minor changes to match publihed versio

La gestion sociale urbaine dans les pays en développement : rapport de fin de recherche mai 1993

Les réflexions proposées ici représentent une étape dans une recherche menée par une équipe du laboratoire TMU sur le thème de "la gestion sociale urbaine dans les pays en développement" ; elle privilégie dans le champ global de la gestion urbaine la dimension sociale, en la considérant comme mécanisme de régulation des rapports sociaux urbains, et comme système de contrôle des populations urbaines. La recherche s'appuie sur l'observation et l'analyse des pratiques des gestionnaires et de celles des citadins, à partir de deux entrées : la régularisation foncière, technique de gestion du sol urbain, mais aussi mode de régulation des rapports sociaux en ville, et la gestion urbaine partagée des services urbains. C'est autour de ces deux axes que s'est tenue une journée de réflexion en mai 1992, qui a permis de mieux cerner les possibilitiés et les limites de la gestion sociale urbaine à son niveau le plus approprié, celui des collectivités territoriales locales. (Résumé d'auteur

Production of topological defects at the end of inflation

Hybrid inflation within supersymmetric grand unified theories, as well as inflation through brane collisions within braneworld cosmological models, lead to the formation of one-dimensional defects. Observational data, mainly from the cosmic microwave background temperature anisotropies but also from the gravitational wave background, impose constraints on the free parameters of the models. I review these inflationary models and discuss the constraints from the currently available data.Comment: 9 pages, Invited talk in the Conference "Challenges in Particle Astrophysics" -- 6th Rencontres du Vietnam, Hanoi (Vietnam) 6-12 Aug. 200

Apport du test de mémoire sémantique 42 items (TMS-42) en consultation mémoire

International audienc

Assessment of semantic memory with the SMT-42

International audienc

Hybrid inflation followed by modular inflation

Inflationary models with a superheavy scale F-term hybrid inflation followed by an intermediate scale modular inflation are considered. The restrictions on the power spectrum P_R of curvature perturbation and the spectral index n_s from the recent data within the power-law cosmological model with cold dark matter and a cosmological constant can be met provided that the number of e-foldings N_HI* suffered by the pivot scale k_*=0.002/Mpc during hybrid inflation is suitably restricted. The additional e-foldings needed for solving the horizon and flatness problems are generated by modular inflation with a string axion as inflaton. For central values of P_R and n_s, the grand unification scale comes out, in the case of standard hybrid inflation, close to its supersymmetric value M_GUT=2.86 x 10^16 GeV, the relevant coupling constant is relatively large (0.005-0.14), and N_HI* is between 10 and 21.7. In the shifted [smooth] hybrid inflation case, the grand unification scale can be identified with M_GUT for N_HI*=21 [N_HI*=18].Comment: 13 pages including 3 figures, uses ws-ijmpa.cls, minor corrections included, talk given at the CTP Symposium on Supersymmetry at LHC: Theoretical and Experimental Perspectives, British University in Egypt (BUE), Cairo, 11-14 March 2007 (to appear in the proceedings

Classification automatique des roulements coniques par reconnaissance des formes floue

Le problème traité dans cette communication s'inscrit dans le cadre de la maintenance préventive et corrective des roulements coniques utilisés sur les matériels roulants de la SNCF. La profusion des méthodes d'investigation et le besoin de structurer les connaissances disponibles ont conduit l'atelier EIMM à mettre en place un système d'aide à l'expertise des roulements qui permette d'optimiser la productivité et la qualité des composants révisés. Pour tenir compte de l'hétérogénéité des données, nous proposons de construire un module de classification par reconnaissance des formes floue qui assure le fonctionnement de la procédure d'expertise. En raison du diagnostic employé qui est essentiellement visuel et tactile, l'analyse d'images est l'alternative proposée. Différents types d'avaries qui interviennent sur des pièces et organes mécaniques du roulement sont analysés et caractérisés. Les résultats obtenus démontrent l'aptitude du module de décision à diagnostiquer les matériels défaillants

Constraints on Supersymmetric Grand Unified Theories from Cosmology

Within the context of SUSY GUTs, cosmic strings are generically formed at the end of hybrid inflation. However, the WMAP CMB measurements strongly constrain the possible cosmic strings contribution to the angular power spectrum of anisotropies. We investigate the parameter space of SUSY hybrid (F- and D- term) inflation, to get the conditions under which theoretical predictions are in agreement with data. The predictions of F-term inflation are in agreement with data, only if the superpotential coupling $\kappa$ is small. In particular, for SUSY SO(10), the upper bound is \kappa\lsim 7\times 10^{-7}. This fine tuning problem can be lifted if we employ the curvaton mechanism, in which case \kappa\lsim 8\times 10^{-3}; higher values are not allowed by the gravitino constraint. The constraint on $\kappa$ is equivalent to a constraint on the SSB mass scale $M$, namely M \lsim 2\times 10^{15} GeV. The study of D-term inflation shows that the inflaton field is of the order of the Planck scale; one should therefore consider SUGRA. We find that the cosmic strings contribution to the CMB anisotropies is not constant, but it is strongly dependent on the gauge coupling $g$ and on the superpotential coupling $\lambda$. We obtain g\lsim 2\times 10^{-2} and \lambda \lsim 3\times 10^{-5}. SUGRA corrections induce also a lower limit for $\lambda$. Equivalently, the Fayet-Iliopoulos term $\xi$ must satisfy \sqrt\xi \lsim 2\times 10^{15} GeV. This constraint holds for all allowed values of $g$.Comment: 32 pages, 7 figures. To match published versio