A generatingfunctionology approach to a problem of Wilf

Wilf posed the following problem: determine asymptotically as $n\to\infty$ the probability that a randomly chosen part size in a randomly chosen composition of n has multiplicity m. One solution of this problem was given by Hitczenko and Savage. In this paper, we study this question using the techniques of generating functions and singularity analysis.Comment: 12 page

Giant anharmonicity suppresses superconductivity in AlH3_3 under pressure

The anharmonic self energy of two zone boundary phonons were computed to lowest order for AlH$_3$ in the $Pm\bar 3n$ structure at 110 GPa. The wavevector and branch index corresponding to these modes are situated in a region of phase space providing most of the electron-phonon coupling. The self energies are found to be very large and the anharmonic contribution to the linewidth of one of the modes studied could be distinguished from the electron-phonon linewidth. It is found that anharmonicity suppresses the electron-phonon coupling parameter $\lambda$, providing a possible explanation for the disagreement between experiment and previous theoretical studies of superconductivity in this system.Comment: 10 pages, 4 figure

The Software behind the Higgs Boson Discovery

In this column, David Rousseau describes the enormous software development effort associated with teasing out evidence for the elusive Higgs boson, a cornerstone of the Standard Model. In keeping with previous Impact columns, everything about this is huge but the application is unique

Compressive Pattern Matching on Multispectral Data

We introduce a new constrained minimization problem that performs template and pattern detection on a multispectral image in a compressive sensing context. We use an original minimization problem from Guo and Osher that uses $L_1$ minimization techniques to perform template detection in a multispectral image. We first adapt this minimization problem to work with compressive sensing data. Then we extend it to perform pattern detection using a formal transform called the spectralization along a pattern. That extension brings out the problem of measurement reconstruction. We introduce shifted measurements that allow us to reconstruct all the measurement with a small overhead and we give an optimality constraint for simple patterns. We present numerical results showing the performances of the original minimization problem and the compressed ones with different measurement rates and applied on remotely sensed data.Comment: Published in IEEE Transactions on Geoscience and Remote Sensin

Little Higgs studies in ATLAS

Study of the possible discovery in Atlas of the new particles predicted by Little Higgs models are presented. Different heavy bosons W_H/Z_H/A_H final states have been studied, with, when relevant, two Higgs mass hypotheses mH=120 GeV and mH=200 GeV. The heavy top T, and the new higgs boson phi++ have also been searched for. The discovery potential of ATLAS is shown to cover a significant portion of the parameter space. This paper is part of the 2006 CERN yellow report : CP studies and non-standard Higgs physics

Propositions pour la masterisation

Sans porter de jugement sur la réforme de masterisation de la formation des maîtres en cours, cette libre opinion, s\u27appuyant sur des enquêtes menées à l\u27échelle locale et nationale, propose des outils de travail collaboratif pour rompre avec la taylorisation des tâches entre les différents acteurs de la formation des maîtres (universités, IUFM, rectorat, établissements du secondaire) et tendre vers une logique de réseau de contribution

Utilisation d’une manette de jeu vidéo pour des expériences de mécanique

Dans cet article sont données les informations pratiques nécessaires à la mise en oeuvre, simple, originale et peu coûteuse, d\u27un contrôleur de jeu vidéo pour mesurer des accélérations. Quelques idées d\u27expériences utilisant ce dispositif sont ensuite indiquées. L\u27intérêt pédagogique d\u27une telle démarche dans le cadre d\u27un enseignement sur la notion de capteur est enfin discuté

Wigner islands with electrons over helium

We present here the first experimental study of Wigner islands formed by electrons floating over helium. Electrons are trapped electrostatically in a mesoscopic structure covered with a helium film, behaving as a quantum dot. By removing electrons one by one, we are able to find the addition spectrum, i.e. the energy required to add (or extract) one electron from the trap with occupation number $N$. Experimental addition spectra are compared with Monte Carlo simulations for the actual trap geometry, confirming the ordered state of electrons over helium in the island.Comment: 12 pages, 13 figures, draft pape