Radial cancellation in spinning sound fields

The radiating part of a circular acoustic source is determined on the basis of an exact analysis of the radiation properties of a source with angular dependence \exp \J n\theta and arbitrary radial dependence. It is found that the number of degrees of freedom in the radiated field is no greater than $k-n$, where $k$ is the wavenumber. The radiating part of the source at low frequency is the wavenumber. The radiating part of the source at low frequency is explicitly stated and used to analyze noise cancellation. The results are applied to the identification of sources in jet noise and an explanation for the low order structure of jet noise fields is proposed.Comment: Submitted to Journal of Fluid Mechanic

Size and charge effects on the deposition of Na on Ar

We discuss the dynamical deposition of the Na atom, the Na$^+$ in and the Na$_6$ cluster on finite Ar clusters mocking up an infinite Ar surface. We analyze this scenario as a function of projectile initial kinetic energy and of the size the target cluster.Comment: 14 pages, 6 figures, Proceedings of the XIth European Workshop on Quantum Systems in Chemistry and Physics (QSCP-XI), Aug. 20-25 2006, St-Petersburg, Russia, submitted to Intern. J. Quant. Che

Classical quasi-trigonometric r−r-matrices of Cremmer-Gervais type and their quantization

We propose a method of quantization of certain Lie bialgebra structures on the polynomial Lie algebras related to quasi-trigonometric solutions of the classical Yang-Baxter equation. The method is based on so-called affinization of certain seaweed algebras and their quantum analogues.Comment: 9 pages, LaTe

Superfluid Phase Stability of 3^3He in Axially Anisotropic Aerogel

Measurements of superfluid $^3$He in 98% aerogel demonstrate the existence of a metastable \emph{A}-like phase and a stable \emph{B}-like phase. It has been suggested that the relative stability of these two phases is controlled by anisotropic quasiparticle scattering in the aerogel. Anisotropic scattering produced by axial compression of the aerogel has been predicted to stabilize the axial state of superfluid $^3$He. To explore this possiblity, we used transverse acoustic impedance to map out the phase diagram of superfluid $^3$He in a $\sim 98$% porous silica aerogel subjected to 17% axial compression. We have previously shown that axial anisotropy in aerogel leads to optical birefringence and that optical cross-polarization studies can be used to characterize such anisotropy. Consequently, we have performed optical cross-polarization experiments to verify the presence and uniformity of the axial anisotropy in our aerogel sample. We find that uniform axial anisotropy introduced by 17% compression does not stabilize the \emph{A}-like phase. We also find an increase in the supercooling of the \emph{A}-like phase at lower pressure, indicating a modification to \emph{B}-like phase nucleation in \emph{globally} anisotropic aerogels.Comment: 4 pages, 4 figures, submitted to LT25 (25th International Conference on Low Temperature Physics

Axionic Membranes

A metal ring removed from a soap-water solution encloses a film of soap which can be mathematically described as a minimal surface having the ring as its only boundary. This is known to everybody. In this letter we suggest a relativistic extension of the above fluidodynamic system where the soap film is replaced by a Kalb-Ramond gauge potential \b(x) and the ring by a closed string. The interaction between the \b-field and the string current excites a new configuration of the system consisting of a relativistic membrane bounded by the string. We call such a classical solution of the equation of motion an axionic membrane. As a dynamical system, the axionic membrane admits a Hamilton-Jacobi formulation which is an extension of the H-J theory of electromagnetic strings.Comment: 15 page

Bernard Bret, Philippe Gervais-Lambony, Claire Hancock et Frédéric Landy, L’espace au prisme de la justice et de l’injustice

Justice et injuste spatiales, dirigé par Bernard Bret, Philippe Gervais-Lambony, Claire Hancock et Frédéric Landy, est le premier ouvrage (2010) d’une nouvelle collection, « Espace et justice », consacrée au thème de la justice spatiale et dirigée par Frédéric Dufaux et Philippe Gervais-Lambony. L’ouvrage regroupe les actes d’un colloque organisé à l’université de Paris-Ouest-Nanterre en mars 2008 et fait référence au lancement en 2009 d’une revue bilingue en ligne (Justice spatiale/Spatial J..

Bernard Bret, Philippe Gervais-Lambony, Claire Hancock et Frédéric Landy, L’espace au prisme de la justice et de l’injustice

Justice et injuste spatiales, dirigé par Bernard Bret, Philippe Gervais-Lambony, Claire Hancock et Frédéric Landy, est le premier ouvrage (2010) d’une nouvelle collection, « Espace et justice », consacrée au thème de la justice spatiale et dirigée par Frédéric Dufaux et Philippe Gervais-Lambony. L’ouvrage regroupe les actes d’un colloque organisé à l’université de Paris-Ouest-Nanterre en mars 2008 et fait référence au lancement en 2009 d’une revue bilingue en ligne (Justice spatiale/Spatial J..

Dynamics of cluster deposition on Ar surface

Using a combined quantum mechanical/classical method, we study the dynamics of deposition of small Na clusters on Ar(001) surface. We work out basic mechanisms by systematic variation of substrate activity, impact energy, cluster orientations, cluster sizes, and charges. The soft Ar material is found to serve as an extremely efficient shock absorber which provides cluster capture in a broad range of impact energies. Reflection is only observed in combination with destruction of the substrate. The kinetic energy of the impinging cluster is rapidly transfered at first impact. The distribution of the collision energy over the substrate proceeds very fast with velocity of sound. The full thermalization of ionic and atomic energies goes at a much slower pace with times of several ps. Charged clusters are found to have a much stronger interface interaction and thus get in significantly closer contact with the surface.Comment: 10 pages, 6 figures, accepted in Euro. Phys. J.