28 research outputs found
Formulation of gauge theories on transitive Lie algebroids
In this paper we introduce and study some mathematical structures on top of
transitive Lie algebroids in order to formulate gauge theories in terms of
generalized connections and their curvature: metrics, Hodge star operator and
integration along the algebraic part of the transitive Lie algebroid (its
kernel). Explicit action functionals are given in terms of global objects and
in terms of their local description as well. We investigate applications of
these constructions to Atiyah Lie algebroids and to derivations on a vector
bundle. The obtained gauge theories are discussed with respect to ordinary and
to similar non-commutative gauge theories.Comment: 30 pages. Final version. arXiv admin note: substantial text overlap
with arXiv:1109.428
Local description of generalized forms on transitive Lie algebroids and applications
In this paper we study the local description of spaces of forms on transitive
Lie algebroids. We use this local description to introduce global structures
like metrics, -Hodge operation and integration along the algebraic part
of the transitive Lie algebroid (its kernel). We construct a \v{C}ech-de Rham
bicomplex with a Leray-Serre spectral sequence. We apply the general theory to
Atiyah Lie algebroids and to derivations on a vector bundle
Théories de jauge et connexions généralisées sur les algébroïdes de Lie transitifs
Transitive Lie algebroids are usually studied from the point of view of the geometry of Poisson. Here, they are preferentially defined in terms of sections of fiber bundle in order to get close to the formalism of the gauge field theory. Then, transitive Lie algebroids can be seen as a generalization of vector fields on the base manifold. This PhD thesis is concerned with the study of generalized connections on transitive Lie algebroids and the construction of gauge theories. Ordinary connections on transitive Lie algebroids are defined as the subset of 1-forms on Lie algebroids with values in its kernel which fulfill a normalization constraint on this kernel. By relaxing this constraint, we build the space of generalized connection 1- forms. Using a background connection, we show that any generalized connections can be decomposed as the sum of an ordinary connection and a purely algebraic parameter defined on the kernel. As in Yang-Mills theories, we define a gauge invariant functional action as the ânormâ of the curvature associated to a generalized connection. Then, the Lagrangian associated to this action forms a Yang-Mills-Higgs type model composed with the field strength associated to gauge fields and a minimal coupling with a tensorial scalar field embedded into a quartic potential. In the case of Atiyah Lie algebroids, the symmetry group of the theory can be reduced by using an appropriate rearrangement of the degrees of freedom in the functional space of fields. We thus obtain a Yang-Mills type theory describing massive vector bosons.Connus des mĂ©caniciens de la gĂ©omĂ©trie de Poisson, les algĂ©broĂŻdes de Lie transitifs sont ici Ă©tudiĂ©s du point de vue de leurs sections afin de dĂ©velopper un formalisme algĂ©brique plus proche de celui dĂ©veloppĂ© par les thĂ©ories de jauge. Ici, les algĂ©broĂŻdes de Lie transitifs s'apparentent Ă une gĂ©nĂ©ralisation des champs de vecteurs sur la variĂ©tĂ© de base. Ce mĂ©moire de thĂšse a pour objet l'Ă©tude des connexions gĂ©nĂ©ralisĂ©es sur les algĂ©broĂŻdes de Lie transitifs et la construction de thĂ©ories de jauge. Les connexions ordinaires sur les algĂ©broĂŻdes de Lie transitifs sont dĂ©finies par des 1-formes de connexion de l'algĂ©broĂŻde de Lie Ă valeurs dans son noyau et vĂ©rifiant une contrainte de normalisation sur ce noyau. En relĂąchant cette contrainte, on construit l'espace des 1-formes de connexions gĂ©nĂ©ralisĂ©es qui se dĂ©composent, Ă l'aide d'une connexion ordinaire de fond, comme la somme d'une connexion ordinaire et d'un paramĂštre purement algĂ©brique dĂ©finit sur le noyau. Dans l'esprit des thĂ©ories Yang-Mills, une action invariante de jauge est dĂ©finie comme la ânormeâ de la courbure associĂ©e Ă une connexion gĂ©nĂ©ralisĂ©e. De cette action, il dĂ©coule un lagrangien composĂ© des termes des thĂ©ories de jauge de type Yang-Mills-Higgs : le terme cinĂ©tique associĂ© aux champs de jauge et le terme de couplage minimal pour un champ tensoriel scalaire plongĂ© dans un potentiel quartique. La rĂ©duction du groupe de symĂ©trie de la thĂ©orie s'effectue par une redistribution des degrĂ©s de libertĂ© dans l'espace fonctionnel des champs de la thĂ©orie. Il rĂ©sulte de ces manipulations la dĂ©finition d'une thĂ©orie de type Yang-Mills dont les bosons vecteurs sont des champs massifs
BCR-associated factors driving chronic lymphocytic leukemia cells proliferation ex vivo
International audienceA chronic antigenic stimulation is believed to sustain the leukemogenic development of chronic lymphocytic leukemia (CLL) and most of lymphoproliferative malignancies developed from mature B cells. Reproducing a proliferative stimulation ex vivo is critical to decipher the mechanisms of leukemogenesis in these malignancies. However, functional studies of CLL cells remains limited since current ex vivo B cell receptor (BCR) stimulation protocols are not sufficient to induce the proliferation of these cells, pointing out the need of mandatory BCR co-factors in this process. Here, we investigated benefits of several BCR co-stimulatory molecules (IL-2, IL-4, IL-15, IL-21 and CD40 ligand) in multiple culture conditions. Our results demonstrated that BCR engagement (anti-IgM ligation) concomitant to CD40 ligand, IL-4 and IL-21 stimulation allowed CLL cells proliferation ex vivo. In addition, we established a proliferative advantage for ZAP70 positive CLL cells, associated to an increased phosphorylation of ZAP70/SYK and STAT6. Moreover, the use of a tri-dimensional matrix of methylcellulose and the addition of TLR9 agonists further increased this proliferative response. This ex vivo model of BCR stimulation with T-derived cytokines is a relevant and efficient model for functional studies of CLL as well as lymphoproliferative malignancies. Like in most mature lymphoproliferative malignancies, an antigenic stimulation is believed to drive the leukemo-genic process in chronic lymphocytic leukemia (CLL) 1-3. A restricted use of IGHV genes and the existence of ste-reotypic B cell receptor (BCR) on CLL cells 4-6 provides evidence in favor of antigenic stimulation where different microbial antigens, as well as auto-antigens, have been suspected as actors of this chronic stimulation 7. In addition , a chronic BCR self-activation has been shown in subtypes of CLL cells 8. Moreover, several signaling aberrations have been described downstream of the BCR, notably in aggressive CLL with unmutated IGHV (UM-CLL), in which the expression of ZAP70 reinforces BCR responsiveness 9-12. BCR activation, which is essential for the physiological development of lymphocytes 13 would also be indispensable for the survival and proliferation of CLL cells in vivo 2. Accordingly, withdrawal of this stimulation is believed to be responsible for the rapid spontaneous apoptosis of CLL cells ex vivo 14. The cellular consequences of this BCR activation has been extensively studied an
Present eternity : quests of temporality in the literary production of the "extrême contemporain" in France (The Writings of Dominique Fourcade and Emmanuel Hocquard)
The term \uab extr\ueame contemporain \ubb is an expression currently used by scholars to indicate the French literary production of the last 20 years. This term was used in a work of literature for the first time by the French poet Dominique Fourcade in 1986 (\uc9l\ue9gie L apostrophe E.C.) in reference to an epoch, but also to a new sense of experiencing time and space in the so-called \uab age of digital reproducibility \ubb. The aim of this paper is to consider how the change in temporal protocols due to the triumph of Big Optics (Paul Virilio) affects the sense of teleology (destiny) and the quest for experience in French contemporary poetry (in particular, in the genre of the elegy). Including both memory and anticipation, the \uab extr\ueame contemporain \ubb production seems to prefer the \u201ctime of now\u201d, Jetz-zeit in Benjamin\u2019s words, to past or testimony, and speaks to the present, whose responsibility is to give voice to a space where everything is simply allowed to happen
Visual Priming Influences Olfactomotor Response and Perceptual Experience of Smells
International audienc
Gauge invariant composite fields out of connections, with examples
17 pagesInternational audienceIn this paper we put forward a systematic and unifying approach to construct gauge invariant composite fields out of connections. It relies on the existence in the theory of a group valued field with a prescribed gauge transformation. As an illustration, we detail some examples. Two of them are based on known results: the first one provides a reinterpretation of the symmetry breaking mechanism of the electroweak part of the Standard Model of particle physics; the second one is an application to Einstein's theory of gravity described as a gauge theory in terms of Cartan connections. The last example depicts a new situation: starting with a gauge field theory on Atiyah Lie algebroids, the gauge invariant composite fields describe massive vector fields. Some mathematical and physical discussions illustrate and highlight the relevance and the generality of this systematic approach
Visual Priming Influences Olfactomotor Response and Perceptual Experience of Smells
International audienc
Super-résolution numérique en holographie par reconstruction régularisée.
International audienceIn-line digital holography (DH) and lensless microscopy are 3D imaging techniques used to reconstruct the volume of micro-objects in many fields. However, their performances are limited by the pixel size of the sensor. Recently, various pixel super-resolution algorithms for digital holography have been proposed. A hologram with improved resolution was produced from a stack of laterally shifted holograms, resulting in better resolved reconstruction than a single low-resolution hologram. Algorithms for super-resolved reconstructions based on inverse problems approaches have already been shown to improve the 3D reconstruction of opaque spheres. Maximum a posteriori (MAP) approaches have also been shown capable of reconstructing the object field more accurately and more efficiently and to extend the usual field-of-view. Here we propose an inverse problem formulation for DH pixel super-resolution and an algorithm that alternates registration and reconstruction steps. The method is described in detail and used to reconstruct synthetic and experimental holograms of sparse 2D objects. We show that our approach improves both the shift estimation and reconstruction quality. Moreover, the reconstructed field-of-view can be expanded by up to a factor 3, thus making it possible to multiply the analyzed area 9 fold.L'holographie numĂ©rique en ligne (DH) et la microscopie sans lentille sont des techniques d'imagerie 3D utilisĂ©es dans de nombreux domaines pour reconstruire des micro-objets dispersĂ©s dans un volume. Cependant, leurs performances sont limitĂ©es par la taille des pixels du capteur. RĂ©cemment, plusieurs algorithmes de super rĂ©solution numĂ©rique ont Ă©tĂ© proposĂ©s pour l'holographie. Un hologramme avec une meilleure rĂ©solution a Ă©tĂ© calculĂ© Ă partir d'une pile d'hologrammes dĂ©calĂ©s latĂ©ralement, produisant une reconstruction mieux rĂ©solue qu'un seul hologramme basse rĂ©solution. Des algorithmes pour des reconstructions super-rĂ©solues basĂ©es sur des approches de problĂšmes inverse ont dĂ©jĂ dĂ©montrĂ©s l'amĂ©lioration de la reconstruction 3D de sphĂšres opaques. Les approches a posteriori maximales (MAP) ont Ă©galement montrĂ©es leur capacitĂ© Ă reconstruire le champ objet plus prĂ©cisĂ©ment et Ă Ă©tendre le champ de vue habituel. Ici, nous proposons une approche "problĂšme inverse" pour faire de la super rĂ©solution numĂ©rique et un algorithme qui alterne les Ă©tapes d'enregistrement et de reconstruction. La mĂ©thode est dĂ©crite en dĂ©tail et utilisĂ©e pour reconstruire des hologrammes synthĂ©tiques et expĂ©rimentaux d'objets discrets 2D. Nous montrons que notre approche amĂ©liore Ă la fois l'estimation du dĂ©calage et la qualitĂ© de la reconstruction. En outre, le champ de vue reconstruit peut ĂȘtre dĂ©veloppĂ© jusqu'Ă un facteur 3, permettant ainsi de multiplier la zone analysĂ©e par neuf
Nouvelles données paléontologiques de la grotte de La Marche (PléistocÚne supérieur, Lussac-les-Chùteaux, Vienne)
International audienceLa grotte de La Marche dĂ©couverte en 1937 par L. PĂ©ricard a fait lâobjet de plusieurs campagnes de fouilles, initiĂ©es dâabord par L. PĂ©ricard lui-mĂȘme, associĂ© Ă S. Lwoff vers la fin des annĂ©es 1930, et conduites ensuite par L. Pradel dans les annĂ©es 1960 et J. Airvaux entre 1988 et 1993. Lâunique niveau du MagdalĂ©nien moyen (datĂ© radiomĂ©triquement 14280 ± 160 ans B.P.) a livrĂ© un ensemble exceptionnel de plaquettes gravĂ©es Ă reprĂ©sentation humaine et Ă figuration animaliĂšre, mais aussi un assemblage diversifiĂ© de vertĂ©brĂ©s comprenant des dents humaines. Notre Ă©tude a Ă©tĂ© menĂ©e sur les rĂ©sidus de tamis de 400 kg de matĂ©riel inĂ©dit issu des campagnes de fouilles et conservĂ© au musĂ©e Sainte-Croix de Poitiers, qui ont Ă©tĂ© triĂ©s et identifiĂ©s au sein de lâiPHEP. Les donnĂ©es obtenues sont concordantes avec la liste faunique Ă©tablie par Pradel en 1960 et Airvaux et al. en 1999, mais permettent de mettre en Ă©vidence Ă partir de restes dentaires lâoccurrence de nouveaux taxons de mammifĂšres tels que les carnivores Panthera,Felis et Crocuta, les genres Sus et Castor et Ă©galement des Phocidae identifiĂ©s par deux dents jugales. Outre cette faune, nous avons identifiĂ© quelques plaques de carapace de chĂ©loniens dulçaquicoles (Emys), associĂ©es Ă des restes dâĂ©lĂ©ments mobiliers (tels que des perles de parure, des silex, des boules dâocre et du charbon) et de matĂ©riel humain comprenant quelques dents dĂ©finitives et dĂ©ciduales, des phalanges, un fragment fĂ©moral et un fragment de maxillaire