An exact master equation for the system-reservoir dynamics under the strong coupling regime and non-Markovian dynamics

In this paper we present a method to derive an exact master equation for a bosonic system coupled to a set of other bosonic systems, which plays the role of the reservoir, under the strong coupling regime, i.e., without resorting to either the rotating-wave or secular approximations. Working with phase-space distribution functions, we verify that the dynamics are separated in the evolution of its center, which follows classical mechanics, and its shape, which becomes distorted. This is the generalization of a result by Glauber, who stated that coherent states remain coherent under certain circumstances, specifically when the rotating-wave approximation and a zero-temperature reservoir are used. We show that the counter-rotating terms generate fluctuations that distort the vacuum state, much the same as thermal fluctuations.Finally, we discuss conditions for non-Markovian dynamics

Moderating effect of economic instability in the relationship between concentration of control and market value: empirical evidence in Latin America

This paper investigates the moderating effect of economic instability in the relationship between the concentration of control and market value of firms. For this purpose, we built an unbalanced panel dataset composed of 341 Latin American companies from six countries: Argentina, Brazil, Chile, Colombia, Mexico, and Peru. The results of the dynamic models, estimated using the systemic generalized method of moments, indicate, in general, that concentration of control only reduces the market value of firms in environments with high economic instability. Thus, this study provides empirical evidence that times of economic instability encourage controlling shareholders to act even more strongly in their own interests, which may result in the expropriation of the wealth of smaller shareholders.info:eu-repo/semantics/publishedVersio

Path Integral Approach to Strongly Nonlinear Composite

We study strongly nonlinear disordered media using a functional method. We solve exactly the problem of a nonlinear impurity in a linear host and we obtain a Bruggeman-like formula for the effective nonlinear susceptibility. This formula reduces to the usual Bruggeman effective medium approximation in the linear case and has the following features: (i) It reproduces the weak contrast expansion to the second order and (ii) the effective medium exponent near the percolation threshold are $s=1$, $t=1+\kappa$, where $\kappa$ is the nonlinearity exponent. Finally, we give analytical expressions for previously numerically calculated quantities.Comment: 4 pages, 1 figure, to appear in Phys. Rev.

Ictiólogos de la Argentina: Juana Yolanda Dziekonska de Ciechomski.

This series will include all those people who, by means of their contributions, great and small, played a part in the consolidation of ichthyology in Argentina. The general plan of this work consists of individual factsheets containing a list of works by each author, along with reference bibliography and, whenever possible, personal pictures and additional material. The datasheets will be published primarily in chronological order, although this is subject to change by the availability of materials for successive editions. This work represents another approach for the recovery and revalorization of those who set the foundations of Argentine ichthyology while in diverse historical circumstances. I expect this to be the beginning of a major work that achieves the description of such a significant part of the history of natural sciences in Argentina

Highly underexpanded jets in the presence of a density jump between an ambient gas and a jet

An experimental research concerning highly underexpanded jets made of different gases from the surrounding ambient is here described. By selecting different species of gases, it was possible to vary the jet-to-ambient density ratio in the 0.04–12 range and observe its effect on the jet morphology. By adjusting the stagnation and ambient pressures, it has been possible to select the Mach number of the jets, independently from the density ratio. Each jet is therefore characterized by its maximum Mach number, ranging from 10 to 50. The Reynolds number range of the nozzle is 103–5×104. The spatial evolution of the jets was observed over a much larger scale than the nozzle diameter. The gas densities were evaluated from the light emission induced by an electron beam and the gas concentrations were obtained by analyzing the color of the emitted light. The results have shown that the morphology of the jets depends to a greater extent on the density ratio. Jets that are lighter than the ambient exhibit a more intense jet-ambient mixing than jets that are heavier than the ambient, while the effects of changing the jet Mach number do not seem to be too large in the explored range. These results can be expressed by means of two simple scaling laws relevant to the near field (pre-Mach-disk) and the mid-long term field (post-Mach-disk), respectively. PRE Kaleidoscope Images: August 2010 http://pre.aps.org/kaleidoscope/August2010/pr