Geometric parametric instability in periodically modulated graded-index multimode fibers

International audienceWe present a theoretical and numerical study of light propagation in graded-index (GRIN) mul-timode fibers where the core diameter has been periodically modulated along the propagation direction. The additional degree of freedom represented by the modulation permits to modify the intrinsic spatiotemporal dynamics which appears in multimode fibers. More precisely, we show that modulating the core diameter at a periodicity close to the self-imaging distance allows to induce a Moiré-like pattern, which modifies the geometric parametric instability gain observed in homogeneous GRIN fibers

Ultraviolet and Infrared Divergences in Implicit Regularization: a Consistent Approach

Implicit Regularization is a 4-dimensional regularization initially conceived to treat ultraviolet divergences. It has been successfully tested in several instances in the literature, more specifically in those where Dimensional Regularization does not apply. In the present contribution we extend the method to handle infrared divergences as well. We show that the essential steps which rendered Implicit Regularization adequate in the case of ultraviolet divergences have their counterpart for infrared ones. Moreover we show that a new scale appears, typically an infrared scale which is completely independent of the ultraviolet one. Examples are given.Comment: 9 pages, version to appear in Mod. Phys. Lett.

Efficient modelling of nonlinear propagation in multimode graded-index fibers

International audienceWe develop an effective 1+1D model describing nonlinear propagation in multimode graded-index fibers. The model is able to quantitatively reproduce recently observed phenomena like geometric parametric instability and broadband dispersive wave emission

Effective Free Energy for Individual Dynamics

Physics and economics are two disciplines that share the common challenge of linking microscopic and macroscopic behaviors. However, while physics is based on collective dynamics, economics is based on individual choices. This conceptual difference is one of the main obstacles one has to overcome in order to characterize analytically economic models. In this paper, we build both on statistical mechanics and the game theory notion of Potential Function to introduce a rigorous generalization of the physicist's free energy, which includes individual dynamics. Our approach paves the way to analytical treatments of a wide range of socio-economic models and might bring new insights into them. As first examples, we derive solutions for a congestion model and a residential segregation model.Comment: 8 pages, 2 figures, presented at the ECCS'10 conferenc

The Second INTEGRAL AGN Catalogue

The INTEGRAL mission provides a large data set for studying the hard X-ray properties of AGN and allows testing of the unified scheme for AGN. We present analysis of INTEGRAL IBIS/ISGRI, JEM-X, and OMC data for 199 AGN supposedly detected by INTEGRAL above 20 keV. The data analysed here allow a significant spectral extraction on 148 objects and an optical variability study of 57 AGN. The slopes of the hard X-ray spectra of Seyfert 1 and Seyfert~2 galaxies are found to be consistent within the uncertainties, whereas higher cut-off energies and lower luminosities are measured for the more absorbed / type 2 AGN. The intermediate Seyfert 1.5 objects exhibit hard X-ray spectra consistent with those of Seyfert 1. When applying a Compton reflection model, the underlying continua appear the same in Seyfert 1 and 2 with photon index 2, and the reflection strength is about R = 1, when assuming different inclination angles. A significant correlation is found between the hard X-ray and optical luminosity and the mass of the central black hole in the sense that the more luminous objects appear to be more massive. There is also a general trend toward the absorbed sources and type 2 AGN having lower Eddington ratios. The black holemass appears to form a fundamental plane together with the optical and X-ray luminosity of the form Lv being proportional to Lx^0.6 M^0.2, similar to that found between radio luminosity Lr, Lx, and M. The unified model for Seyfert galaxies seems to hold, showing in hard X-rays that the central engine is the same in Seyfert 1 and 2, but seen under different inclination angles and absorption. (Abridged)Comment: 26 pages, 16 figures, accepted for publication in A&A. Corrections by language editor included in version

Participatory Plant Breeding in Uruguay

The introduction of forage legumes into the native pastures of Uruguay is considered an environmentally safe method with which to increase the level of production through the addition of biologically fixed nitrogen. An integrated plant breeding programme was initiated at INIA (National Agricultural Research Institute), Uruguay, with the aim of developing forage legumes able to persist and produce in co-existence with the native (grass dominant) vegetation under cattle and sheep grazing. The programme was conducted in parallel with rhizobial strain selection. During 1998 to 2001 at Glencoe Research Station (32o 01\u2732 S lat; 57o 00o 39 W long), 326 temperate and subtropical forage legume species were evaluated in the basaltic region of Uruguay. This study provided a set of data with which the legume species could be ranked according to their performance (Real et al., 2004) so that the best 10% could be selected for further evaluation and breeding. The best species according to objectively measured characters (i.e. forage and seed yield) could be very valuable to certain farming systems and farmers, but might be of little value for other farmers and their systems. A significant relationship between the farm decision making unit and the farming systems has been reported for this region (Ferreira, 1997). Participatory research has proved to be an effective way to include farmers\u27 local knowledge in plant breeding programmes (Dusseldorp & Box, 1993).Therefore, to aid the conventional plant breeding approach, a farmer participatory breeding group was formed