Self-propelled particles convert energy from their surrounding environment into translational motion. Collectively, they are generically able to inject local energy into the macroscopic motion of the whole system, thus sustaining an orientationally ordered stationnary state in two dimensions. In this talk, I will discuss the transition between this polar state (whose existence is forbidden for equilibrium systems) and the less exotic isotropic state. A key observation is that the interaction of self-propelled particles does not conserve momentum. I will show how this can be made more quantitative in the dilute regime, in order to obtain predictions on the transition between isotropic and polar phases. Although the theory is general, I will focus the discussion on a model of self-propelled hard discs that was already shown to describe very well a vibrated grain experiment. The quantitative predictions of the theory are checked against data from molecular dynamics simulations. I will finally discuss our recent findings about how density effects alter the mean-field transition.

Il existe plusieurs raisons pour l'augmentation de la résistance électrique dans un champ magnétique (magnétorésistance positive). Par contre, la magnétorésistance négative est rare et pas très bien comprise. Récemment, quelques études expérimentales ont démontré une très forte magnétorésistance négative des électrons deux-dimensionnels à basses températures, voir un exemple en attaché (Q. Shi et al, 2014).

L'explication qu'on propose est basée sur l'idée de considérer les électrons comme un fluide visqueux. La résistance est donc proportionnelle à la viscosité électronique et la chute de résistance est due à la diminution de la viscosité en champ magnétique.

We introduce a set of pseudo-observables (PO) characterizing the properties of Higgs decays in generic SM extensions with no new particles below the Higgs mass. The PO represent a systematic generalization of the "kappa-framework" so far adopted by the LHC experiments, providing a useful bridge between data and theory predictions (EFTs or models). We analyze how they can be used to test various dynamical and symmetry hypotheses about the Higgs sector. We discuss the bounds on the Higgs PO implied by EW constraints, under the assumption that the Higgs particle is the massive excitation of an SU(2)L doublet. Using such bounds, detailed predictions for various h->4l observables are presented.

Cell mechanics is fundamental in many cellular processes both in physiological and pathological situations. The actin cytoskeleton is responsible for the main part of this mechanics. In cells, actin filaments are very dynamic polymers spatially organized by many different partners. Rheological studies have been devoted to the understandings of the mechanical properties of actin gels assembled in absence or in presence of actin binding partners showing very interesting behaviors. We developed a new approach based on magnetic particles and the use of the Arp2/3 machinery to assemble and study mechanically actin networks which are close to the ones found in the lamellipodium of a migrating cell. The idea is to use dipolar attractive forces that develops between superparamagnetic micro-sized objects to deform in a controlled way dense branched actin networks grown from the surface of the particles. The main advantage of this technique in the context of biophysics is its high throughput that allows reliable measurements to be performed. We carried out a first study which established the link between elastic properties of these networks and their architecture and give insights into the origin of the elasticity in dense branched actin networks assembled from a mix of purified proteins. We also began to study actin networks assembled from yeast extracts with more than 80 proteins present in the network. This kind of gels shows a strong plasticity which was absent from the purified system. We also developed new particles with flat surfaces that allow non linear measurements to be done and growth under constraints to be followed. These new developments open the ways to study cell mechanics at the scale of isolated cells and even at the scale of a tissue.

Most studies of the atomic structure of glasses, especially non-metallic ones, are conducted at
high temperatures and - in terms of modeling - often from the supercooled phase of the melt. That
comes because X-ray and neutron-scattering techniques cannot unambiguously resolve the
intermediate- and long-range atomic structure of amorphous solids. For insulating glasses the
continuously random network model of Zachariasen-Warren has dominated the field in the West since
the 1930s, though in the Soviet Block the antagonist concept of crystallites and cellular superclusters
has held fast to the post up to these days (see for example the polycluster concept of A.S.Bakai).
In this talks the case for an intermediate picture of the glassy structure will be advocated,
looking at the glassy state from its frozen end (at low and very low temperatures) as one would do with
a crystal. The new tool to watch with is proposed to be those remnant degrees of freedom in the
otherwise frozen matrix of a glass that are still ergodic and are dynamical defects known as tunneling
systems. These are normally modeled in terms of simple tunneling two-level systems, sitting in a
medium with a flat distribution of their relevant parameters – a legacy from Zachariasen-Warren.
However, the two-level systems picture – though partly successful - is not capable of describing many
experiments at low temperatures in a consistent way, notably: experiments contradicting the standard
tunneling model, and especially the magnetic and composition effects that are hard to explain with this
simple picture. It will be shown that a demise of the Zachariasen-Warren dogma and a refined cellular-
type structural model for the intermediate-range atomic structure can lead, when folded in the
tunneling-systems concept, to a much improved explanation of most experiments with cold glasses1
and to an improved picture of the atomic structure. Perhaps, also to the mechanism for the glass
transition.

The new cellular picture for the intermediate atomic structure of a glass will be introduced and
the implementation of the tunneling model, with two very distinct tunneling species on such structure
will be shown to lead to a quantum-mechanical theory for the remnant effective degrees of freedom
capable of explaining all experiments so far. Also, predictions for exotic new magnetic effects2 will be
made, so that the atomic structure of glasses will be accessible through new, tunneling, magnetic eyes.
In the first talk, the basic concepts of glassy atomic structure and of tunneling states (or
systems) will be introduced, with an overview of the results – and puzzles – achieved by means of the
standard 1972 tunneling model of Phillips and of Anderson, Halperin & Varma. The emphasis will
be on concepts and the justification (yet non-existent) of the models, no details will be given.
In the second talk, the major puzzles opened by the low-temperature physics of glasses will be
introduced and an overview of our resolution of these difficulties will be presented, with a sample of
some of the most striking results obtained in Como in the last 10-15 years. The emphasis will again be
on concepts and now on the mature and profound justification of the extended tunneling model,
which rests upon a new picture of the intermediate-range glassy atomic structure, on a clear
identification of the nature of the (two types of) tunneling states and the justification of the exotic
magnetic effects in real glasses (silicates, but also a-Si, chalcogenides and organics, multi-component
or contaminated single-component) at low but – and here is the novelty – all the way to room
temperatures.

[1] G.Jug, M.Paliienko and S.Bonfanti, J.Non-Cryst.Solids 401 (2014) 66-72;
[2] S.Bonfanti and G.Jug, J.Low-Temp.Phys. (2015 in print) (arXiv: 1504.05722v1)

Most studies of the atomic structure of glasses, especially non-metallic ones, are conducted at
high temperatures and - in terms of modeling - often from the supercooled phase of the melt. That
comes because X-ray and neutron-scattering techniques cannot unambiguously resolve the
intermediate- and long-range atomic structure of amorphous solids. For insulating glasses the
continuously random network model of Zachariasen-Warren has dominated the field in the West since
the 1930s, though in the Soviet Block the antagonist concept of crystallites and cellular superclusters
has held fast to the post up to these days (see for example the polycluster concept of A.S.Bakai).
In this talks the case for an intermediate picture of the glassy structure will be advocated,
looking at the glassy state from its frozen end (at low and very low temperatures) as one would do with
a crystal. The new tool to watch with is proposed to be those remnant degrees of freedom in the
otherwise frozen matrix of a glass that are still ergodic and are dynamical defects known as tunneling
systems. These are normally modeled in terms of simple tunneling two-level systems, sitting in a
medium with a flat distribution of their relevant parameters – a legacy from Zachariasen-Warren.
However, the two-level systems picture – though partly successful - is not capable of describing many
experiments at low temperatures in a consistent way, notably: experiments contradicting the standard
tunneling model, and especially the magnetic and composition effects that are hard to explain with this
simple picture. It will be shown that a demise of the Zachariasen-Warren dogma and a refined cellular-
type structural model for the intermediate-range atomic structure can lead, when folded in the
tunneling-systems concept, to a much improved explanation of most experiments with cold glasses1
and to an improved picture of the atomic structure. Perhaps, also to the mechanism for the glass
transition.

The new cellular picture for the intermediate atomic structure of a glass will be introduced and
the implementation of the tunneling model, with two very distinct tunneling species on such structure
will be shown to lead to a quantum-mechanical theory for the remnant effective degrees of freedom
capable of explaining all experiments so far. Also, predictions for exotic new magnetic effects2 will be
made, so that the atomic structure of glasses will be accessible through new, tunneling, magnetic eyes.
In the first talk, the basic concepts of glassy atomic structure and of tunneling states (or
systems) will be introduced, with an overview of the results – and puzzles – achieved by means of the
standard 1972 tunneling model of Phillips and of Anderson, Halperin & Varma. The emphasis will
be on concepts and the justification (yet non-existent) of the models, no details will be given.
In the second talk, the major puzzles opened by the low-temperature physics of glasses will be
introduced and an overview of our resolution of these difficulties will be presented, with a sample of
some of the most striking results obtained in Como in the last 10-15 years. The emphasis will again be
on concepts and now on the mature and profound justification of the extended tunneling model,
which rests upon a new picture of the intermediate-range glassy atomic structure, on a clear
identification of the nature of the (two types of) tunneling states and the justification of the exotic
magnetic effects in real glasses (silicates, but also a-Si, chalcogenides and organics, multi-component
or contaminated single-component) at low but – and here is the novelty – all the way to room
temperatures.

[1] G.Jug, M.Paliienko and S.Bonfanti, J.Non-Cryst.Solids 401 (2014) 66-72;
[2] S.Bonfanti and G.Jug, J.Low-Temp.Phys. (2015 in print) (arXiv: 1504.05722v1)

[1] François Molino (L2C): situation de l'IRM et du contexte pathologique en neurosciences (20 min)
On présentera un rapide survol de la modélisation des fonctions cérébrales et du type de données disponibles. On se focalisera ensuite sur l'imagerie de connectivité structurale et fonctionnelle par IRM, et on montrera la place de ces données dans les stratégies de modélisation du cerveau. On mettra finalement l'accent sur l'originalité et l'abondance des données disponibles à Montpellier.
[2] Emmanuelle Le Bars (INM) : les techniques d’imagerie de la connectivité (25 min)
On présentera pour commencer l'imagerie structurale de connectivité (tenseur de diffusion), passant en revue l'acquisition, le traitement des données, leur signification: cartes, tractographie déterministe et probabiliste. On s'intéressera ensuite à l'imagerie dite de resting state fMRI et à la connectivité fonctionnelle, développant à nouveau d'abord l'acquisition puis l'approche simplifiée du traitement des données par analyse en composantes indépendantes.
[3] Nicolas Menjot de Champfleur (INM) : validation clinique des approches de connectivité (25 min)
On présentera successivement sur différentes pathologies des validations de la connectivité anatomique, puis de la connectivité fonctionnelle, en insistant sur les phénomènes de plasticité cérébrale. On développera enfin le projet de validation des cartographies par utilisation des donnée peropératoires disponibles à Montpellier, l'importance potentielle de cette approche, et la nécessité de nouvelles modélisations.

Among the nitride alloy semiconductor structures used in various devices, AlInGaN epilayer can give more freedom in adjusting lattice constants and band gaps independently. The AlInGaN epilayer with an appropriate composition ratio can be grown as lattice matched to InGaN and can be used as electron blocking layer or window layer in solar cells. Therefore, the quaternary AlInGaN is a promising candidate towards enhancing electrical/optical confinement and minimizing mismatch-induced strain at the same time.
In the present lecture, MOCVD growth and characterization of InGaN/GaN quantum wells and AlInGaN/GaN will be presented. High resolution X-ray diffraction, photoluminescence, time resolved photoluminescence, Raman spectroscopy and atomic force microscopy have been employed to study the structural and optical properties of the heterostructures. The results are correlated with growth parameters and crystalline quality of the materials.

The status of the wave function has been the subject of active debates since the very birth of quantum theory. What is it? Does it represent reality, or our knowledge of it? A general framework has recently been developed, allowing one to address these questions formally. In late 2011 Pusey, Barrett and Rudolph (PBR) proved a breakthrough theorem, suggesting that the knowledge interpretation was not tenable [1]. I will review these results and present new developments, showing in particular that the knowledge interpretation cannot (fully) explain the indistinguishability of nonorthogonal quantum states [2].

[1] M. F. Pusey, J. Barrett, T. Rudolph, Nat. Phys. 8, 475–478 (2012).
[2] J. Barrett et al., Phys. Rev. Lett. 112, 250403 (2014); M. S. Leifer, Phys. Rev. Lett. 112, 160404 (2014); C. Branciard, Phys. Rev. Lett. 113, 020409 (2014).