5,885 research outputs found
Affine Dunkl processes
We introduce the analogue of Dunkl processes in the case of an affine root
system of type . The construction of the affine Dunkl
process is achieved by a skew-product decomposition by means of its radial part
and a jump process on the affine Weyl group, where the radial part of the
affine Dunkl process is defined as the unique solution of some stochastic
differential equation. We prove that the affine Dunkl process is a c\`adl\`ag
Markov process as well as a local martingale, study its jumps, and give a
martingale decomposition, which are properties similar to those of the
classical Dunkl process
Quantum random walks and minors of Hermitian Brownian motion
Considering quantum random walks, we construct discrete-time approximations
of the eigenvalues processes of minors of Hermitian Brownian motion. It has
been recently proved by Adler, Nordenstam and van Moerbeke that the process of
eigenvalues of two consecutive minors of an Hermitian Brownian motion is a
Markov process, whereas if one considers more than two consecutive minors, the
Markov property fails. We show that there are analog results in the
noncommutative counterpart and establish the Markov property of eigenvalues of
some particular submatrices of Hermitian Brownian motion
Combining parameter values or -values
We review the methods to combine several measurements, in the form of
parameter values or -values.Comment: 15 pages, 4 figure
Hydrodynamics of galaxy mergers with supermassive black holes: is there a last parsec problem ?
We study the formation of a supermassive black hole (SMBH) binary and the
shrinking of the separation of the two holes to sub-pc scales starting from a
realistic major merger between two gas-rich spiral galaxies with mass
comparable to our Milky Way. The simulations, carried out with the Adaptive
Mesh Refinement (AMR) code RAMSES, are capable of resolving separations as
small as 0.1 pc. The collision of the two galaxies produces a gravo-turbulent
rotating nuclear disk with mass (10^9 Msun) and size (60 pc) in excellent
agreement with previous SPH simulations with particle splitting that used a
similar setup (Mayer et al. 2007) but were limited to separations of a few
parsecs. The AMR results confirm that the two black holes sink rapidly as a
result of dynamical friction onto the gaseous background, reaching a separation
of 1 pc in less than 10^7 yr. We show that the dynamical friction wake is well
resolved by our model and we find good agreement with analytical predictions of
the drag force as a function of the Mach number. Below 1 pc, black hole pairing
slows down significantly, as the relative velocity between the sinking SMBH
becomes highly subsonic and the mass contained within their orbit falls below
the mass of the binary itself, rendering dynamical friction ineffective. In
this final stage, the black holes have not opened a gap as the gaseous
background is highly pressurized in the center. Non-axisymmetric gas torques do
not arise to restart sinking in absence of efficient dynamical friction, at
variance with previous calculations using idealized equilibrium nuclear disk
models. (abridged)Comment: Accepted for publication in MNRAS. 10 pages, 6 figure
A possible chiral spin-liquid phase in non-centrosymmetric BaCoO
Based on a symmetry approach, we propose a possible explanation of the weak
ferromagnetic component recently observed in YBaCoFeO (Valldor et al.
Phys Rev B, 224426 (2011)) and other isostructural compounds in the
high-temperature spin-liquid phase. Due to the polar nature of their crystal
structure, a coupling between time-odd scalar spin chirality which we suggest
as the primary order parameter and macroscopic magnetization is possible as
follows from the general form of the appropriate free-energy invariant. The
deduced pseudoproper coupling between both physical quantities provides a
unique possibility to study the critical behaviour of the chiral order
parameter
: L'adstrat juridique cinématographique comme soutien pédagogique du document authentique
International audienceThis article proposes to portray the different steps of a learning scenario created for students enrolled in the first year of the Grenoble law school who chose English as a foreign language as part of their curriculum. The court room extract that can be found in the film Vera Drake may be used as resource material to be copied according to the pedagogic strategy which aims at creating authentic tasks for the learner in English for Specific Purposes (ESP). The students are required to perform a task coherent with their professional goal, that is to say, they will be expected to act a prominent scene from a criminal trial. This article will describe how the scenario is led by the necessity to perform meaningful tasks using the target language and also uses an article taken from the Times, law supplement, as a "legal words" tool box and inspiration to create the denunciative context necessary to perform the play.Cet article propose de décrire les activités d'un scénario pédagogique, réalisé pour des étudiants de première année de droit de la faculté de Grenoble dans le cadre de l'apprentissage de l'anglais de spécialité. L'adstrat professionnel juridique que l'on trouve dans le film Vera Drake peut servir de support dans une démarche de pédagogie de projet qui vise l'authenticité de tâches menées par les étudiants, à savoir la mise en scène d'une étape d'un procès au pénal selon le modèle de l'adstrat professionnel. L'article montrera comment le projet, piloté par l'objectif d'appropriation de la langue et culture de spécialité, utilise dans un second temps le document authentique, un article du Times, puisé dans la rubrique " law supplement ", comme outil lexical et de création de contexte énonciatif pour réaliser la tâche finale
Orbital ordering promotes weakly-interacting S=1/2 dimers in the triangular lattice compound Sr3Cr2O8
The weakly interacting S=1/2 dimers system Sr3Cr2O8 has been investigated by
powder neutron diffraction and inelastic neutron scattering. Our data reveal a
structural phase transition below room temperature corresponding to an
antiferro-orbital ordering with nearly 90 degrees arrangement of the occupied
3z^2-r^2 d-orbital. This configuration leads to a drastic reduction of the
inter-dimer exchange energies with respect to the high temperature
orbital-disorder state, as shown by a spin-dimer analysis of the
super-superexchange interactions performed using the Extended Huckel Tight
Binding method. Inelastic neutron scattering reveals the presence of a quasi
non-dispersive magnetic excitation at 5.4 meV, in agreement with the picture of
weakly-interacting dimers
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