Archives Séminaires 2012-2013

Séminaire exceptionnel

Séminaire IPAG de Guy Pelletier (IPAG), lundi 10 septembre 2012 à 11h00, IPAG seminar room

1re partie (1/2 heure), présentation générale des idées, des faits et des conséquences en physique des particules et cosmologie ; (présentation Power Point). mi-temps : ceux pour qui ce sera suffisant peuvent quitter la salle. 2eme partie (1/2 heure + éventuelle prolongation pour les passionnés), davantage de détail pour ceux qui veulent en savoir plus (en grande partie au tableau) : Approche variationnelle et groupe de symétrie. Qu’est-ce qu’un groupe de jauge ? Comment fonctionne le (…)

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Séminaire IPAG de Alexandre Marcowith (LUPM, Montpellier), jeudi 12 septembre 2012 à 11h00, IPAG seminar room

2012 marks the centenary of cosmic rays discovery by Austrian physicist Victor Hess. Although the origin of this cosmic rays remains a major puzzles for modern astrophysics, in the recent years our understanding of this phenomenon has greatly improved thanks to observations (notably at the highest energies), progress in the microphysics of shock and phenomenology of transport in the interstellar medium. In this seminar we will present these various aspects, and we will discuss open questions (…)

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Séminaire IPAG de Benoît Cerutti (University of Colorado), jeudi 20 septembre 2012 à 11h00, IPAG seminar room

The unexpected detection of bright short-lived gamma-ray flares in the Crab Nebula in 2010, has attracted considerable interests among observers and theorists. This discovery implies that electrons and positrons are accelerated to PeV (10^15 eV) energies in a milliGauss magnetic field, challenging the most established models of particle acceleration and pulsar wind nebulae. In this talk, I will argue that the flares could be powered by the rapid dissipation of magnetic energy via magnetic (…)

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Séminaire IPAG de Eric Herbst (U. of Virginia), jeudi 27 septembre 2012 à 11h00, IPAG seminar room

The exciting new spectral results from the Herschel Space Observatory, SOFIA (Stratospheric Observatory for Infrared Astronomy), and ALMA (Atacama Large Millimeter/Submillimeter Array) among other telescopes are leading astrochemists into a new era, in which our current level of understanding of the molecular universe will be challenged as never before. New observations of both reasonably well-known and novel environments with exquisite spatial detail plus vastly increased spectral intensity (…)

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Séminaire IPAG de Philippe Zarka (Obs. de Meudon), jeudi 4 octobre 2012 à 11h00, IPAG seminar room

Je présenterai une revue du sujet, depuis la découverte de la première exoplanète autour d’un pulsar jusqu’aux recherches actuelles avec les radiotélescopes géants LOFAR, UTR-2 et GMRT. Ces recherches ont motivé le développement d’un cadre théorique pour les interactions "plasma" étoile-planète, que je décrirai. J’insisterai enfin sur l’intérêt particulier de la détection radio si elle est atteinte.

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Séminaire IPAG de Willy Kley (University of Tubingen), jeudi 11 octobre 2012 à 11h00, IPAG seminar room

As planets form and grow within gaseous protoplanetary disks, the mutual gravitational interaction between the disk and planet leads to the exchange of angular momentum, and migration of the planet. I review the current understanding of disk-planet interactions, focussing in particular on physical processes that determine the speed and direction of migration. The role of Lindblad and corotation torques as a function of the disk properties will be discussed, as well as the evolution of (…)

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Séminaire IPAG de Fabrizio Fiore (Osservatorio Astronomico di Roma), jeudi 18 octobre 2012 à 11h00, IPAG seminar room

AGN observations and evolutionary studies can be used to investigate the physics of baryon transformation in galaxies and the cosmological framework. I will present a pilot program to push the search of unobscured and obscured AGN up to z=5-6 and discuss the astrophysical and cosmological perspectives of this line of research. Targeting high-z supermassive black holes (SMBHs), the structures with the fastest (exponential) growth rate, can help investigating the evolution of the Universe at (…)

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Observing supernova remnants (SNRs) and modelling the shocks they are associated with is the best way to quantify the energy SNRs re-distribute back into the interstellar medium (ISM), and estimate the mass of the shocked component. In my talk, I will present recent observations, mostly from the APEX, SOFIA (CO), and Spitzer (H2) telescopes, of various SNRs , including W28, W44, 3C391, and IC443. I will then show how comparisons with shock models constitute a valuable tool to constrain both (…)

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Séminaire IPAG de Panayotis Lavvas (U. Reims), jeudi 8 novembre 2012 à 11h00, IPAG seminar room

Photochemical processes allow the formation of increasing complexity molecular structures. Depending of the chemical potential of each environment this process can eventually proceed to the production of large enough molecular structures that start to behave as particles, following the laws of microphysical evolution (photochemical aerosols).
Saturn’s largest moon, Titan, provides us a unique opportunity to study the atmospheric molecular growth and the mechanisms affecting it. The (…)

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Séminaire IPAG de Antoine Rozel (Univ. Roma), jeudi 15 novembre 2012 à 11h00, IPAG seminar room

The charaterization of the surface of Venus indicates an homogeneous age of 500 to 700 Myrs. This observation suggests that the lithosphere of the planet may have experienced a catastrophic overturn after a sudden lithosphere distabilisation. The mechanisms involved in this event are still largely misunderstood. Enceladus, an icy satellite of Saturn, presents a very important heat flux in its south pole. Though some significant heating may be explained by tidal dissipation, no model has been (…)