Quark Transverse Charge Densities for Spin-3/2 Particles
Cédric Lorcé (Mainz)

Les origines de la science moderne (4)
Maurice Gabriel (AGO, Liège)

La Mission Symbol-X: focaliser sur le ciel en X durs
Philippe Ferrando (CEA, Paris, France)

Meteorites, the oldest rocks of the solar system.
Herbert Palme (Forschungsinstitut und Naturmuseum Senckenberg, Frankfurt am Main, Allemagne)

Les origines de la science moderne (5)
Maurice Gabriel (AGO, Liège)

Les galaxies naines bleues compactes et l'univers primordial
Trinh Xhuan Thuan (Université de Virginie, USA)

Les origines de la science moderne (6)
Maurice Gabriel (AGO, Liège)

Le séminaire portera sur l'évolution de la science au 16e siècle, avec:

1. en mathématiques, les algébristes italiens, Simon Stevin et François Viète
2. en astronomie, Copernic, Tycho Brahé et Giordano Bruno
3. en physique, les avancées en balistique, en statique, en optique, en magnétisme et Francis Bacon.

Perspectives de production de J/psi et Upsilon au LHC.
Jean-Philippe Lansberg (SLAC National Accelerator Laboratory, Stanford U., USA)

Je discuterai les différents mécanismes potentiellement impliqués dans la production de quarkonium lourd dans les collisions pp à la lumière des récents calculs des corrections QCD au NLO et NNLO pour les transitions singulet et octet de couleur. Je discuterai également les contributions venant de la coupure dans la voie s dans les transitions singulet de couleurs. A chaque fois, je confronterai les résultats obtenus avec les mesures expérimentales venant du Tevatron et de RHIC et présenterai les prédictions pour le LHC. Par ailleurs, je discuterai l'utilité et la faisabilité au LHC de mesures de nouvelles observables ayant pour but de mieux discriminer les différents mécanismes de production possibles.

Hadronic form factors in non-leptonic heavy meson decays
Bruno El-Bennich (Argonne National Laboratory & Université Pierre et Marie Curie, France)

In this talk I will concentrate on hadronic effects in non-leptonic B and D meson decays into three light mesons, such as pions and kaons. These B decays, in particular, are important as they give rise to some of the strongest CP violation amplitudes that have been reported by the BaBar and Belle collaborations, but one can also regard both B and D decays as a laboratory to study the whole spectrum of pion-pion and pion-kaon resonance spectrum observed in the corresponding Dalitz plots. Calculations within the framework of QCD factorization have not been generally found to be in contradiction with experiment. Nonetheless, in certain non-leptonic decay channels there are inconsistencies between theoretical predictions of branching ratios and their experimental values. Our contribution here is to improve the Standard Model calculations with a particular focus on non-perturbative effects due to light meson final-state interactions encoded in hadronic scalar and vector form factors.

Processus de transport dans les intérieurs stellaires
Stéphane Mathis (Commissariat à l'énergie atomique (CEA) / Service d'astrophysique, France)

Avec l'exploitation scientifique du satellite CoRoT et le lancement prochain de la mission KEPLER, l'astérosismologie va amener des contraintes de plus en plus fines sur les intérieurs stellaires et sur les processus de transport dont ils sont le siège. Durant ce séminaire, je rappellerai l'ensemble de ces mécanismes physiques pour ensuite présenter un état de l'art détaillé de la modélisation de chacun d'entre eux et les enjeux à venir.

La formation et la propagation des jets dans les étoiles T-Tauri et les AGNs
Zakaria Meliani (KU Leuven, Belgique)

Collimated outflows occur in many astrophysical environments. They are seen in young stellar objects, proto-planetary nebulae, compact objects, Active Galactic Nuclei and Gamma Ray Bursts. Though they differ vastly in scale, speed and energy, astrophysical jets show a remarkable similarity in their morphology.

In this talk I'll give an overview of the theoretical aspects of jet launching and collimation while also focusing on the computational side. I will present a numerical simulation of non-ideal magnetohydrodynamical (MHD) stellar winds coupled with disc-driven jets where the resistive and viscous accretion disc is self-consistently described. Our simulations show that the inner outflow is accelerated from the central object hot corona thanks to both the thermal pressure and the Lorentz force. In our framework, the thermal acceleration is sustained by the heating produced by the dissipated magnetic energy due to the turbulence. Conversely, the outflow launched from the resistive accretion disc is mainly accelerated by the magneto-centrifugal force. In the second part, I will talk about the transverse stability in 2D and 3D of the relativistic two-component jets in the case of Faranoff-Riley type I.

Distributions of Night Airglow and the Variability in Venus’ Atmosphere: NCAR VTGCM Simulations
Amanda Brecht (University of Michigan, Ann Arbor, USA)

The National Center for Atmospheric Research (NCAR) thermospheric general circulation model for Venus (VTGCM) is producing results that are comparative to Pioneer Venus and Venus Express data. The model is a three dimensional model that can calculate temperatures, zonal winds, meridional winds, vertical winds, and concentration of specific species. The VTGCM can also compute the O2-IR and NO-UV night airglow intensity distributions. The altitude range has been stretched to cover 80 km to 200 km on the nightside. Sensitivity test with the eddy diffusion coefficient and the wave drag term have been completed. With the expansion of the altitude grid and the range of sensitivity tests, the VTGCM is able to show consistent set of results with the nightside temperature and the night airglows. These results can show possible controlling parameters of the O2-IR, NO-UV night airglow layers, and the nightside hot spot. Being able to understand the night airglow distribution and variability provides valuable insight into the changing circulation of Venus’ upper atmosphere and leads to an overall planetary perception of the atmospheric dynamics.

QCD resummation for Drell-Yan-like processes beyond the Standard Model
Benjamin Fuks (IPHC - U. Strasbourg, France)

When studying the transverse-momentum (pT) distribution of a produced colorless final state, it is convenient to separate the large- and small-pT regions. For the large values of pT the use of the fixed-order perturbation theory is fully justified, but in the small-pT region, the coefficients of the perturbative expansion are enhanced by powers of large logarithmic terms. Furthermore, at the production threshold, the mismatch between virtual corrections and phase-space suppressed real-gluon emission leads also to the appearance of large logarithmic terms. Accurate calculations of pT-spectrum and invariant mass distribution must then include soft-gluon resummation in order to obtain reliable perturbative predictions and properly take these logarithmic terms into account.

We implement the transverse-momentum, threshold and joint resummation formalisms at the next-to-leading logarithmic accuracy and consistently match the obtained result with the pure perturbative result at the first order in the strong coupling constant. We present precision calculations for SUSY particle pair production at hadron colliders, give numerical predictions, and compare the various resummed cross sections with the perturbative results. We confront then the results obtained with the next-to-leading order Monte Carlo generator MC@NLO and with the leading-order Monte Carlo generator PYTHIA to joint resummation in the framework of Z' models. The impact of scale and parton densities dependences, as well as non-perturbative effects, are also studied.

Les origines de la science moderne (7 et fin)
Maurice Gabriel (AGO, Liège)

Ce dernier séminaire portera sur le dix-septième siècle. Nous y développerons en priorité l'évolution qui a rendu possible l'apparition de la mécanique de Newton. Avec:

1. Kepler et Galilée
2. Gassendi, le retour de l'atomisme et le principe d'inertie. Ainsi que les débuts de l'atomisme en Angleterre
3. La mécanique de Descartes et sa conception du monde
4. Newton et la naissance des Principia

En fonction du temps encore disponible, on abordera le problème du vide et de la pression atmosphérique et éventuellement les travaux en optique.

The Effects of Magnetic Fields and Rotation on Massive Star Winds
Asif ud-Doula (Morrisville State College, USA)

Based on MHD simulation study of magnetic channeling in radiatively driven stellar winds, I examine here the dynamical effects of stellar rotation in the 2-D axisymmetric case of an aligned dipole surface field.

We characterize the stellar rotation in terms of a parameter W(=Vrot/Vorb) (the ratio of the equatorial surface rotation speed to orbital speed). We find that rotation effects are weak for models with Alfven radius (RA) smaller than the Kepler co-rotation radius (RK), RA < RK, but can be substantial and even dominant for models with RA > RK. In particular, by extending our simulations to very strong magnetic confinement case, we find that these do indeed show clear formation of the rigid-body disk predicted in previous analytic models, with however a rather complex, dynamic behavior characterized by both episodes of downward infall and outward breakout that limit the buildup of disk mass.

Overall, the results provide an intriguing glimpse into the complex interplay between rotation and magnetic confinement, and form the basis for a full MHD description of the rigid-body disks expected in strongly magnetic Bp stars like Sigma Ori E.

Cosmoparticle physics - fundamental relationship between modern cosmology and particle physics
Maxim Yu. Khlopov (Moscow Engineering Physics Institute and Center for Cosmoparticle physics ; Cosmion and Virtual Institute of Astroparticle physics, APC Laboratory, Paris, France)

Development of particle physics and cosmology lead to their inevitable fundamental relationship. The modern cosmology is based on inflationary models with baryosynthesis and dark energy/matter. The reasons for inflation, baryosynthesis and dark matter/energy and their realisation on the physics beyond the standard model are discussed. Models of inflation, baryosynthesis and extensive list of dark matter candidates are presented. Cosmological models and physics, on which they are based, can be tested in the combination of physical, astrophysical and cosmological probes.

Cosmoarcheology - astrophysical data as the "experimental sample" for cosmological test of new physics
Maxim Yu. Khlopov (Moscow Engineering Physics Institute and Center for Cosmoparticle physics ; Cosmion and Virtual Institute of Astroparticle physics, APC Laboratory, Paris, France)

Extensions of standard model lead to new metastable particles, reflecting new conservation laws that folloow from particle symmetry. Their presence in the Universe can be tested in confrontation with the data on light element abundance, data on cosmic microwave background on formation of large scale structure of the Universe and on nonthermal electromagnetic backgrounds and cosmic rays.

Cosmophenomenology of new physics
Maxim Yu. Khlopov (Moscow Engineering Physics Institute and Center for Cosmoparticle physics ; Cosmion and Virtual Institute of Astroparticle physics, APC Laboratory, Paris, France)

Together with new particles cosmological consequences of particle models can lead to cosmological defects (like monopoles, cosmic strings or domain walls) and various primordial nonlinear structures. Phase transitions in early Universe, reflecting the pattern of symmetry breaking, mechanisms of inflation and baryosynthesis can lead to formation of primordial mini black holes, clusters of massive black holes or antimatter domains.

En hommage à Jacques Demaret :

Le principe anthropique
Dominique Lambert (FUNDP, Namur)

Le 3 juin 2009 il y aura dix ans que notre collègue et ami Jacques Demaret nous quittait à l'âge de 56 ans. Nous avons voulu marquer cet anniversaire en organisant, le 4 juin prochain, une petite cérémonie dont le point principal sera un séminaire sur un sujet qui lui tenait à coeur.
Pour ceux qui n'ont pas eu la chance de le connaître, Jean-Pierre Swings et Yves De Rop évoqueront brièvement son souvenir. Ensuite Dominique Lambert nous donnera un séminaire portant sur un sujet qui, avec la recherche de la vie dans l'univers, trouve un regain d'actualité et dont le titre est celui d'un livre qu'il avait écrit avec Jacques: "Le Principe Anthropique: L'Homme est-il le centre de l'Univers?"

Résumé du séminaire:
Nous montrerons comment les études pionnières de Jacques Demaret sur le principe anthropique annonçaient en fait des développements récents concernant non seulement la cosmologie mais aussi l'exobiologie. Nous montrerons en outre que les approches épistémologiques originales de Jacques Demaret ont contribué aussi de manière significative à une juste appréciation de la portée et des limites des "énoncés anthropiques".

Puzzles of dark matter searches
Maxim Yu. Khlopov (Moscow Engineering Physics Institute and Center for Cosmoparticle physics ; Cosmion and Virtual Institute of Astroparticle physics, APC Laboratory, Paris, France)

Direct and indirect searches for dark matter lead to serious problems for simple models with stable neutral Weakly Interacting Massive Particles (WIMPs) as candidates for dark matter. A possibility of new stable quarks and charged leptons - bound in neutral atom-like composite dark matter species to explain these puzzles is discussed.

Numerical simulations of gamma-ray-induced cascades in extragalactic magnetic field
Andrii Elyiv (Main Astronomical Observatory, Ukraine)

High energy photons coming to Earth’s atmosphere produce the showers of the secondary particles. The spatial distribution of the Cherenkov emission from such showers can be then used for the reconstruction of parameters of the incoming particles. But along the way from source to atmosphere the gamma-photons are subjected to influence of astrophysical environment. First of all, gamma-rays from the source interact with the infrared/optical photon background producing secondary electrons and positrons, which emit secondary rays via inverse Compton scattering of cosmic microwave background photons. In this way gamma-photon induces the electro-magnetic cascade in extragalactic medium. At the same time magnetic fields, mainly extragalactic, can deflect the secondary electrons and positrons from rectilinear motion and cause the modification of the observed shape of source.

We present the results of Monte-Carlo simulations of three-dimensional electromagnetic cascade in the intergalactic medium. The deflection of the secondary electrons in the cascade lead to extended 0.1-10 degree scale emission at multi-GeV and TeV energies around extragalactic sources of very-high-energy gamma-rays. Using Monte-Carlo simulated data sets, we demonstrate that the dependence between the extended emission surface brightness profile and extragalactic magnetic field allows to measure weak magnetic fields with magnitudes in the range from < 1e-16 G to 1e-12 G if they exist in the voids of the Large Scale Structure.

Neogene atmospheric carbon dioxide proxy records – a comparison
Wolfram M. Kuerschner (Institute of Environmental Biology, Palaeoecology, Utrecht University, Utrecht)

The Neogene is characterized by a series of key climatic events that lead to the founding of the Late Cenozoic icehouse mode and the dawn of modern biota. The processes that caused these developments and particularly the role of atmospheric CO₂ as a forcing factor is controversially discussed. During this seminar I will present the different marine and terrestrial CO₂ proxy records and their implications for climate and the terrestrial biosphere during the Neogene.

Physical properties of isolated galaxies and small galaxy groups
Olga Melnyk (AGO, Liège)

We consider the physical and morphological properties and dark matter content of isolated galaxies, pairs and triplets. We also discuss the different methods of their identification.

We introduce the two catalogs of isolated galaxies: within the Local Supercluster with radial velocities V_LG<3500 km/s and the all-sky catalog of isolated galaxies selected from 2MASS. These galaxies may be considered as a reference samples to study environmental effects in galaxy structure and evolution.

Geometric method based on the high-order 3D Voronoi tessellation is proposed for identifying the single galaxies, pairs and triplets. This approach allows to select small galaxy groups and isolated galaxies in different environment and find the isolated systems. We found that systems in the denser environment have greater rms velocity and mass-to-luminosity ratio.

X-ray observations of the hot gas halos (~ 107 K) within galaxy pairs provide the information about the merging processes and dark matter distribution in these systems. We considered X-ray properties of two pairs of early type galaxies observed with XMM-Newton.

Developments in phase mask coronagraphy at JPL and Palomar
Eugene Serabyn (JPL, Pasadena, USA)

The imaging and spectroscopy of arbitrary exoplanets around nearby stars remains extremely challenging. However, phase mask coronagraphs are of great interest in this regard, because of their small inner working angles and high throughput. Indeed, the vortex coronagraph has been identified as one of the two coronagraphs closest to ideal in performance. This talk will cover our recent work in developing phase masks and in demonstrating their capabilities on ground based telescopes. Use of a four-quadrant phase mask coronagraph on our ExAO-level well corrected subaperture at Palomar has yielded detections of known brown dwarf companions as close as 2.8 lambda/D from their host stars, and debris disk structures to within 1.5 lambda/D. We are now developing vector vortex coronagraphic masks, in which an azimuthal phase spiral is generated by a rotationally symmetric half-wave plate made out of hardened liquid crystals. These vortex masks already perform very well, with a demonstrated contrast at 3 lambda/D of about a part in a million. While this level is already of interest for ground-based use, further improvements are planned to reach the rejection levels needed for terrestrial exoplanet detection.

Séminaire en videoconférence :

Cosmic-ray signatures of dark matter decay
Alejandro Ibarra (Universität München)

Atomic diffusion in F- and G-type stars
Andreas Korn (Uppsala, Suède)

Due to their longevity and rich spectra, main-sequence stars between 5000 and 6500 K play a key role in studies of Galactic chemical evolution. Traditionally, it has been assumed that the surface abundances of such stars reflect the composition of the birth clouds, as the outer layers of such stars are well mixed by convection. But in recent years, empirical evidence has made us realize that, on the level of accuracy required for chemical-evolution studies, the abundances are shaped by internal mixing processes collectively referred to as atomic diffusion, a notion theoretically expected since the 1980s. In this talk, I will give an overview of what has been found, what the implications of these findings are and where this field is going.

Spin Physics: the Sivers and the Boer-Mulders functions in two quark models.
Aurore Courtois (Universitad de Valencia)

In this seminar, my aim will be to give a glimpse of recent progress in Spin Physics. This newly categorized field of hadronic physics has gathered a growing interest, as it is mainly related to the role of the transverse polarization of quarks and nucleons. In particular I will focus on two distribution functions whose definitions are allowed by the existence of leading-twist Final State Interactions, i.e. the Sivers and the Boer-Mulders functions. Theoretically it is expected that these two distribution functions can account for non-trivial transverse spin and momentum correlations such as Single-Spin Asymmetries in hard scattering processes such as Semi-Inclusive Deep Inelastic Scattering or Drell-Yan processes. Experiments are being performed at HERMES, COMPASS and RHIC as well as proposed at, e.g., JLab to test those hypotheses by measuring the corresponding asymmetries in such processes.
There exist very few evaluations of those two distribution functions. In this seminar, I will present the results that we recently obtained for the evaluation of the Sivers and the Boer-Mulders function in two quark models. The performances of the MIT bag model and a simple Constituent Quark Model are shown to both lead to the trend defined by the experiments and first principles properties. These formalisms allow for a "transparency" at the quark level with insight into the role of the helicity of the quarks.

The analysis of spectroscopic line profile variations in gamma Doradus and SPB type variables
Duncan Wright (Observatoire Royal, Bruxelles)

The gamma Doradus and SPB stars show high radial order (n), low degree (l), gravity-mode non-radial pulsation with periods from 0.3-3 days. I will explain the procedure used to obtain and analyse a high quality time-series of spectral line profiles of these stars and highlight the difficulties in determining the degree l, and azimuthal order m of any pulsations found in the data. Finally I will show some of our recent results for a few SPB and gamma Doradus stars from our multi-site campaigns.

Clumpy Lenses: Finding Subhalos in Lens Galaxies
Ross Fadely (Rutgers University)

In the modern framework of Cold Dark Matter (CDM), galaxies form hierarchically through mergers with smaller satellite galaxies. High resolution N-body simulations generically predict a large number of such satellites surrounding both local and distant galaxies. Observationally, the confirmation of the number (as a function of mass) of these subhalos has been challenging. Fortunately, gravitational lensing provides a unique tool for finding small scale structure. By using multi-wavelength measurements of flux ratios of lensed quasars, we can study lensing effects on many scales, allowing a direct probe of substructure properties. On-going work has revealed that this technique can strongly constrain the masses of dark matter clumps, permitting tests of CDM at cosmological distances.

Host galaxies of z > 1 Active Galactic Nuclei
Isabelle Gavignaud (Astrophysikalisches Institut Potsdam)

The discovery of the tight correlation between black hole mass and galactic bulges a decade ago has drawn a large interest. Since the observations of AGN is currently the only way to study super-massive black holes up to cosmologically significant look-back times, the study of AGN host galaxies is currently an obvious path to follow when trying to understand the link between black hole and bulge growth. This seminar will report on observational results obtained with recent HST/NICMOS observation of z~1.4 AGN galaxy.

A propos de la couche limite et du seeing en atmosphère libre à Concordia
Eric Fossat (Université de Nice-Sofia-Antipolis)

La station franco-italienne Concordia sur le haut plateau Antarctique pourrait devenir un important site astronomique grâce à ses propriétés de transparence infra-rouge uniques au monde. De plus elle offre l'opportunité d'y bénéficier d'un seeing bien meilleur que sur les meilleurs sites en exploitation, pourvu que le télescope soit situé au dessus de la couche limite très turbulente d'une trentaine de mètres d'épaisseur en moyenne. Créée par la combinaison d'un gradient thermique et d'un gradient de vitesse de vent, cette couche turbulente a une hauteur très nettement limitée à tout instant, mais variable dans le temps. J'exposerai les résultats statistiques obtenus sur cette hauteur, sur le contenu en énergie turbulente de cette couche limite, sur les autres paramètres de la turbulence, et sur le seeing hors couche limite, qui est effectivement largement meilleur que tout autre, même s'il reste un facteur limitant par rapport aux observations spatiales.

Un monde parfait: l'astronomie mathématique grecque
Anne Tihon (Université Catholique de Louvain)

L'astronomie mathématique grecque s'est constituée à l'époque hellénistique, dans un milieu privilégié, Alexandrie, lorsque, après les conquêtes d'Alexandre, le monde grec classique a éclaté pour se trouver directement en contact avec les civilisations orientales, babylonienne et égyptienne. Dans notre exposé, nous montrerons à l'aide de quelques textes, les grandes caractéristiques de la mentalité grecque ; nous montrerons ensuite l'apport de l'astronomie babylonienne pour arriver aux grands astronomes de l'Antiquité, Hipparque (ca 150 a. C.) et Ptolémée (ca 140 p. C.). Nous présenterons en détail l'œuvre astronomique de ce dernier, et les prolongements de celle-ci à travers les siècles.

Radial-velocity observations with a new Poznan Spectroscopic Telescope
Agata Rozek (AGO / Poznan)

We present results of radial velocity measurements obtained with Poznan Spectroscopic Telescope (PST). The telescope has been operating since August 2007. The PST is equipped with two 50cm diameter mirrors of Newtonian focus, connected by an optic fiber with an echelle spectrograph. The PSTs design aimed at the best cooperation with the spectrograph as well as limiting light looses. It allows us to measure radial velocity of stars as faint as 11.5 magnitudes. The peltier-liquid cooled CCD camera covers 64 echelle orders with a spectral range of 4500A. The dispersion of the obtained radial velocity measurements is on the level of 150 m/s. Echelle spectra reduction and RV measurements are performed with Image Reduction and Analysis Facility (IRAF). Radial velocity measurements are done for pulsating stars, eclipsing binaries and other types of variables.

Poor Clusters with High Relative Velocity Central Dumbbell Galaxies
Hernán Quintana (Pontificia Universidad Catolica de Chile)

We will present three examples of poor clusters or groups which have dominant dumbbell galaxies. Spectroscopic data show these dumbbells are the result of the merging of a secondary group infalling into the cluster, containing one of the components, while the original cluster is centered on the other component. The high velocity and limited tidal effects suggest these examples are ongoing mergers, which happen to occur with a small angle to the line of vision.

The chemical composition of the Orion star forming region: stars, gas, and dust
Sergio Simon-Diaz (Instituto de Astrofisica de Canarias (Tenerife, Espagne))

The Orion star forming region is an ideal laboratory for many astrophysical studies. In this talk I will present an study of the chemical composition of early B-type stars in the Orion OB1 association. The main ideas I will talk about are: (1) The importance of self-consistent spectroscopic techniques for the abundance analyzes in this type of stellar objects; (2) the study of the homogeneity of abundances in stars from the various stellar subgroups in OriOB1; (3) the comparison of O stellar abundances with recent Solar determinations; (4) the comparison of stellar abundances with those resulting from the analysis of the emission line spectra of the Orion nebula (M42); (5) the study of the oxygen depletion onto dust grains in the Orion nebula.

Reconstructing Holocene climate using a climate model and proxy data: Model strategy and preliminary results
Kerstin Haberkorn (Meteorological Institute, University of Hamburg)

An Earth system model of intermediate complexity (Planet Simulator; PlaSim) is used to reconstruct Holocene climate based on proxy data. The Planet Simulator is a general circulation model (GCM) suitable for paleoclimate research. Its easy handling and the modular structure allow for fast and problem dependent simulations. This approach uses a data assimilation technique to incorporate proxy time series into PlaSim to initialize paleoclimate simulations. For this, the following strategy is applied: The sensitivities of the terrestrial PlaSim climate are determined with respect to sea surface temperature (SST) anomalies. Here, the focus is the impact of regionally varying SST both in the tropics and in the Northern Hemisphere mid-latitudes. The inverse of these sensitivities is used to determine the SST necessary for the nudging of land and coastal proxy climates. Preliminary results indicate the potential and the limitations of the method. Within the German Science Foundation priority project INTERDYNAMIK, PlaSim is then combined with a socio-technological evolution model (GLUES) to provide improved knowledge on the shift from hunting-gathering to agropastoral subsistence societies during the Holocene.

Diagnostics sismiques des étoiles de type solaire : apports de la mission spatiale CoRoT
Sébastien Deheuvels (Paris-Meudon)

L'analyse et l'interprétation des pulsations stellaires offrent l'opportunité de contraindre la structure interne des étoiles, ainsi que leur évolution. Dans les pulsateurs de type solaire, la détection de ces oscillations est difficile, du fait de leur très faible amplitude. Les oscillations du Soleil ont été largement étudiées depuis le milieu des années 1970, mais ce n'est que très récemment, avec l'arrivée de spectrographes haute résolution, et des missions spatiales comme CoRoT, que ce type d'oscillations a pu être détecté et analysé dans d'autres étoiles que le Soleil.

Nous présenterons dans un premier temps les méthodes et les enjeux de l'analyse des données sismiques, dans le cadre des oscillations de type solaire. On insistera sur le saut qualitatif que représente l'arrivée de jeux de données de longue durée et quasiment ininterrompus tels que ceux obtenus avec le satellite CoRoT. L'argumentation s'appuiera sur les analyses d'objets CoRoT déjà étudiés.

L'analyse des spectres d'oscillation permet d'obtenir un certain nombre d'indicateurs sismiques, qui sont utilisés par la suite comme autant d'observables supplémentaires pour contraindre les modèles des étoiles étudiées. Les fréquences des modes d'oscillation sont sensibles à l'intérieur de l'étoile, et peuvent être porteuses d'information sur les phénomènes encore mal connus de la structure stellaire, comme par exemple les processus de transport aux interfaces entre zones radiatives et zones convectives. On présentera le cas d'une étoile de faible masse, où l'existence d'un coeur convectif est établie par le biais d'un diagnostic sismique. On s'intéressera ensuite à une cible CoRoT plus évoluée. L'interprétation des fréquences de ses modes d'oscillation permet de montrer qu'elle a passé la fin de la Séquence Principale, et brûle de l'hydrogène en couche.

Aspects of the two-Higgs-doublet model in the framework of gauge invariant functions
Markos Maniatis (Heidelberg University)

Two-Higgs doublet models belong to the most favoured extensions of the Standard Model. In the framework of gauge invariant functions the study of general THDM's simplifies considerably. Different aspects are discussed in this approach like the search for the global minima, CP symmetries, and symmetries preserved by the renormalization group equations.

Saturn's rapidly rotating magnetosphere: New results from Cassini.
Emma Bunce (Lecturer in Planetary Science, University of Leicester, UK)

Since July 2004, the joint NASA/ESA Cassini-Huygens mission to Saturn and Titan has undertaken the first in depth study of the Saturn system including investigations of the planet, its ring system, the orbiting moons, and the magnetosphere. Major results and mysteries from the mission so far span a range of topics such as the elusive planetary rotation rate, the discovery of geysers on Enceladus, and new evidence for a ring around the moon Rhea. As well as introducing such general highlights from the mission, a particular focus of this talk will be on the effects of Saturn's rapidly rotating magnetosphere and the origins of Saturn's dynamic auroral emissions.

Transverse-momentum dependent parton densities: renormalization properties and evolution
Igor Cherednikov (INFN, Cosenza)

Recently obtained results on transverse-momentum dependent parton densities ("TMDs"), which are the important ingredients for the description of semi-inclusive hadronic processes at high energy, are presented. Special attention is payed to the renormalization group properties of these objects. In particular, their leading-order anomalous dimension is calculated in the light-cone gauge with different possible additional gauge-fixing conditions. It is shown that the RG properties can be used to reveal, in the most economic way, the general structure of the gauge links entering the operator definition of TMDs. The high-energy evolution of TMDs, as well as the problems of factorization in semi-inclusive hadronic processes, are discussed.

Unitarization and experiments at LHC
Oleg Selyugin (JINR, Dubna)

The investigations are tightly connected with the experimental programs at the LHC (TOTEM and ATLAS). For the experiments at the LHC, it is important to determine the "asymptotic" behavior of the hadron elastic scattering amplitude, in particular the effects of the saturation of the unitarity limit. The positivity of the imaginary part of the scattering amplitude is enforced by the condition SS+ = 1 for the scattering matrix of the two particles.
On the basis of non-linear equations, which mimic parton saturation in the non-perturbative regime, we developed unitarization schemes in the impact parameter representation of the hadron scattering amplitude that map it to the circle of unitarity. In connection with different unitarization schemes the asymptotic S-matrix can be equal to zero or minus unity. On the basis of integral dispersion relations the asymptotic properties of S-matrix corresponding to the different classes of the unitarization schemes is examined. Using the different forms of the energy dependence of the imaginary part of the scattering amplitude we show that, in order to reproduce the data, the fits choose amplitudes that correspond to an asymptotic value S equal zero, hence to the Black Disk Limit (BDL). The BDL will lead to a severe change in the t dependence of the real part and of the slope of the elastic scattering amplitude in the region of small t, and in turn this may bias the measurement of the total cross section. We examine this issue, and suggest new strategies to test the reliability of the total cross section measurements.