κ\kappa-deformation, affine group and spectral triples

A regular spectral triple is proposed for a two-dimensional $\kappa$-deformation. It is based on the naturally associated affine group $G$, a smooth subalgebra of $C^*(G)$, and an operator \caD defined by two derivations on this subalgebra. While \caD has metric dimension two, the spectral dimension of the triple is one. This bypasses an obstruction described in \cite{IochMassSchu11a} on existence of finitely-summable spectral triples for a compactified $\kappa$-deformation.Comment: 29 page

Flow field computations for blunt bodies in planetary environments

Numerical analysis on flow distribution around hypersonic blunt body in planetary atmospher

Motion clouds: model-based stimulus synthesis of natural-like random textures for the study of motion perception

Choosing an appropriate set of stimuli is essential to characterize the response of a sensory system to a particular functional dimension, such as the eye movement following the motion of a visual scene. Here, we describe a framework to generate random texture movies with controlled information content, i.e., Motion Clouds. These stimuli are defined using a generative model that is based on controlled experimental parametrization. We show that Motion Clouds correspond to dense mixing of localized moving gratings with random positions. Their global envelope is similar to natural-like stimulation with an approximate full-field translation corresponding to a retinal slip. We describe the construction of these stimuli mathematically and propose an open-source Python-based implementation. Examples of the use of this framework are shown. We also propose extensions to other modalities such as color vision, touch, and audition

Formation of a rotating jet during the filament eruption on 10-11 April 2013

We analyze multi-wavelength and multi-viewpoint observations of a helically twisted plasma jet formed during a confined filament eruption on 10-11 April 2013. Given a rather large scale event with its high spatial and temporal resolution observations, it allows us to clearly understand some new physical details about the formation and triggering mechanism of twisting jet. We identify a pre-existing flux rope associated with a sinistral filament, which was observed several days before the event. The confined eruption of the filament within a null point topology, also known as an Eiffel tower (or inverted-Y) magnetic field configuration results in the formation of a twisted jet after the magnetic reconnection near a null point. The sign of helicity in the jet is found to be the same as that of the sign of helicity in the filament. Untwisting motion of the reconnected magnetic field lines gives rise to the accelerating plasma along the jet axis. The event clearly shows the twist injection from the pre-eruptive magnetic field to the jet.Comment: 14 pages, 12 figures, to appear in MNRA

Fibroblast Growth Factor 22 Is Not Essential for Skin Development and Repair but Plays a Role in Tumorigenesis

PMCID: PMC3380851This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

The dimension of loop-erased random walk in 3D

We measure the fractal dimension of loop-erased random walk (LERW) in 3 dimensions, and estimate that it is 1.62400 +- 0.00005. LERW is closely related to the uniform spanning tree and the abelian sandpile model. We simulated LERW on both the cubic and face-centered cubic lattices; the corrections to scaling are slightly smaller for the face-centered cubic lattice.Comment: 4 pages, 4 figures. v2 has more data, minor additional change

Modeling electricity loads in California: a continuous-time approach

In this paper we address the issue of modeling electricity loads and prices with diffusion processes. More specifically, we study models which belong to the class of generalized Ornstein-Uhlenbeck processes. After comparing properties of simulated paths with those of deseasonalized data from the California power market and performing out-of-sample forecasts we conclude that, despite certain advantages, the analyzed continuous-time processes are not adequate models of electricity load and price dynamics.Comment: To be published in Physica A (2001): Proceedings of the NATO ARW on Application of Physics in Economic Modelling, Prague, Feb. 8-10, 200

Multigroup radiation hydrodynamics with flux-limited diffusion and adaptive mesh refinement

International audienceContext. Radiative transfer plays a crucial role in the star formation process. Because of the high computational cost, radiation-hydrodynamics simulations performed up to now have mainly been carried out in the grey approximation. In recent years, multifrequency radiation-hydrodynamics models have started to be developed in an attempt to better account for the large variations in opacities as a function of frequency.Aims. We wish to develop an efficient multigroup algorithm for the adaptive mesh refinement code RAMSES which is suited to heavy proto-stellar collapse calculations.Methods. Because of the prohibitive timestep constraints of an explicit radiative transfer method, we constructed a time-implicit solver based on a stabilized bi-conjugate gradient algorithm, and implemented it in RAMSES under the flux-limited diffusion approximation.Results. We present a series of tests that demonstrate the high performance of our scheme in dealing with frequency-dependent radiation-hydrodynamic flows. We also present a preliminary simulation of a 3D proto-stellar collapse using 20 frequency groups. Differences between grey and multigroup results are briefly discussed, and the large amount of information this new method brings us is also illustrated.Conclusions. We have implemented a multigroup flux-limited diffusion algorithm in the RAMSES code. The method performed well against standard radiation-hydrodynamics tests, and was also shown to be ripe for exploitation in the computational star formation context