The twilight zone in the parametric evolution of eigenstates: beyond perturbation theory and semiclassics

Considering a quantized chaotic system, we analyze the evolution of its eigenstates as a result of varying a control parameter. As the induced perturbation becomes larger, there is a crossover from a perturbative to a non-perturbative regime, which is reflected in the structural changes of the local density of states. For the first time the {\em full} scenario is explored for a physical system: an Aharonov-Bohm cylindrical billiard. As we vary the magnetic flux, we discover an intermediate twilight regime where perturbative and semiclassical features co-exist. This is in contrast with the {\em simple} crossover from a Lorentzian to a semicircle line-shape which is found in random-matrix models.Comment: 4 pages, 4 figures, improved versio

An efficient, parametric fixpoint algorithm for analysis of java bytecode

Abstract interpretation has been widely used for the analysis of object-oriented languages and, in particular, Java source and bytecode. However, while most existing work deals with the problem of flnding expressive abstract domains that track accurately the characteristics of a particular concrete property, the underlying flxpoint algorithms have received comparatively less attention. In fact, many existing (abstract interpretation based—) flxpoint algorithms rely on relatively inefHcient techniques for solving inter-procedural caligraphs or are speciflc and tied to particular analyses. We also argüe that the design of an efficient fixpoint algorithm is pivotal to supporting the analysis of large programs. In this paper we introduce a novel algorithm for analysis of Java bytecode which includes a number of optimizations in order to reduce the number of iterations. The algorithm is parametric -in the sense that it is independent of the abstract domain used and it can be applied to different domains as "plug-ins"-, multivariant, and flow-sensitive. Also, is based on a program transformation, prior to the analysis, that results in a highly uniform representation of all the features in the language and therefore simplifies analysis. Detailed descriptions of decompilation solutions are given and discussed with an example. We also provide some performance data from a preliminary implementation of the analysis

New record of Abelisauroid Theropods from the Bauru group (upper cretaceous), São Paulo State, Brazil

Isolated bones of abelisauroid theropods from the Bauru Group (Late Cretaceous, Brazil), are described. They correspond to three individuals represented by fused ischia and part of the ilium, a partial axis, and a right fi bula, respectively. The fossils come from different sites in the municipalities of Ibirá (axis and fi bula) and Monte Alto (ilium and ischia), São Paulo State, from Maastrichtian beds of the São José do Rio Preto and the Marília formations (Bauru Group), respectively. The specimens provide new information on abelisauroids which are still poorly known in the Brazilian fossil record, and on the distribution of this diverse group of theropod dinosaurs in South America. These discoveries indicate that abelisauroids were the most common large predatory dinosaurs in the outcrops where they come from.Ossos isolados de terópodes abelissauroides do Grupo Bauru (Cretáceo Superior), Brasil, são descritos. O material consiste de restos de três indivíduos, um representado pelos ísquios fusionados e parte do ílio, outro por um fragmento de áxis e outro por uma fíbula direita. Os fósseis, oriundos dos municípios de Ibirá (áxis e fíbula) e Monte Alto (ílio e ísquios fusionados), Estado São Paulo, foram descobertos em depósitos maastrichtianos das formações São José do Rio Preto e Marília (Grupo Bauru), respectivamente. Os espécimes fornecem novas informações sobre abelissauroides, ainda são pouco conhecidos no registro fóssil brasileiro, e sobre a distribuição deste grupo diverso de dinossauros terópodes na América do Sul. Estas descobertas indicam que os abelissauroides foram os grandes dinossauros predadores mais comuns nos afl oramentos de onde eles provêm.Fil: Méndez, Ariel Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; ArgentinaFil: Novas, Fernando Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Iori, Fabiano V.. Universidade Federal do Rio de Janeiro; Brasi

Qualitative Analysis of Causal Cosmological Models

The Einstein's field equations of Friedmann-Robertson-Walker universes filled with a dissipative fluid described by both the {\em truncated} and {\em non-truncated} causal transport equations are analyzed using techniques from dynamical systems theory. The equations of state, as well as the phase space, are different from those used in the recent literature. In the de Sitter expansion both the hydrodynamic approximation and the non-thermalizing condition can be fulfilled simultaneously. For $\Lambda=0$ these expansions turn out to be stable provided a certain parameter of the fluid is lower than 1/2. The more general case $\Lambda>0$ is studied in detail as well.Comment: RevTeX file, 23 pages. Accepted for publication in J. Math. Phy

Cultivating Sustainable Coffee: Persistent Paradoxes

This chapter discusses the relationship and interconnections among changing the livelihoods of farmers, initiatives for sustainable coffee, and the production of shade-grown coffee. It examines the advantages and opportunities for farmers and producers engaged in coffee certification and diversification programs. The role of Fair Trade and organic networks in creating awareness of biodiversity conservation, the social and environment costs of coffee systems, and the need for supporting small farmers are also discussed. The methods to increase accountability and improve the efficiency of coffee cooperatives are presented in this chapter, as are the importance of understanding the sustainability initiatives and their implications for the regulators, along with the use of land patterns for coffee cultivation

Optimal search strategies of space-time coupled random walkers with finite lifetimes

We present a simple paradigm for detection of an immobile target by a space-time coupled random walker with a finite lifetime. The motion of the walker is characterized by linear displacements at a fixed speed and exponentially distributed duration, interrupted by random changes in the direction of motion and resumption of motion in the new direction with the same speed. We call these walkers "mortal creepers". A mortal creeper may die at any time during its motion according to an exponential decay law characterized by a finite mean death rate $\omega_m$. While still alive, the creeper has a finite mean frequency $\omega$ of change of the direction of motion. In particular, we consider the efficiency of the target search process, characterized by the probability that the creeper will eventually detect the target. Analytic results confirmed by numerical results show that there is an $\omega_m$-dependent optimal frequency $\omega=\omega_{opt}$ that maximizes the probability of eventual target detection. We work primarily in one-dimensional ($d=1$) domains and examine the role of initial conditions and of finite domain sizes. Numerical results in $d=2$ domains confirm the existence of an optimal frequency of change of direction, thereby suggesting that the observed effects are robust to changes in dimensionality. In the $d=1$ case, explicit expressions for the probability of target detection in the long time limit are given. In the case of an infinite domain, we compute the detection probability for arbitrary times and study its early- and late-time behavior. We further consider the survival probability of the target in the presence of many independent creepers beginning their motion at the same location and at the same time. We also consider a version of the standard "target problem" in which many creepers start at random locations at the same time.Comment: 18 pages, 7 figures. The title has been changed with respect to the one in the previous versio