Taxes in a simple wealth distribution model by inelastically scattering particles

In this work we use an inelastic scattering process of particles to propose a model able to reproduce the salient features of the wealth distribution in an economy by including taxes to each trading process and redistributing that collected among the population according to a given criterion. Additionally, we show that different optimal levels of taxes may exist depending on the redistribution criterion.Comment: 7 pages, 7 figure

Dyson-Schwinger Equations and the Quark-Gluon Plasma

We review applications of Dyson-Schwinger equations at nonzero temperature, T, and chemical potential, mu, touching topics such as: deconfinement and chiral symmetry restoration; the behaviour of bulk thermodynamic quantities; the (T,mu)-dependence of hadron properties; and the possibility of diquark condensation.Comment: 13 pages, 1 figure, LaTeX, sprocl.sty, epsfig.sty. Summary of presentations by the authors at the Workshop "Understanding Deconfinement in QCD", ECT*, Trento, 1-13/March, 199

Psychological factors affecting equine performance

For optimal individual performance within any equestrian discipline horses must be in peak physical condition and have the correct psychological state. This review discusses the psychological factors that affect the performance of the horse and, in turn, identifies areas within the competition horse industry where current behavioral research and established behavioral modification techniques could be applied to further enhance the performance of animals. In particular, the role of affective processes underpinning temperament, mood and emotional reaction in determining discipline-specific performance is discussed. A comparison is then made between the training and the competition environment and the review completes with a discussion on how behavioral modification techniques and general husbandry can be used advantageously from a performance perspective

Unnested islands of period-doublings in an injected semiconductor laser

We present a theoretical study of unnested period-doubling islands in three-dimensional rate equations modeling a semiconductor laser subject to external optical injection. In this phenomenon successive curves of period doublings are not arranged in nicely nested islands, but intersect each other. This overall structure is globally organized by several codimension-2 bifurcations. As a consequence, the chaotic region existing inside an unnested island of period doublings can be entered not only via a period-doubling cascade but also via the breakup of a torus, and even via the sudden appearance of a chaotic attractor. In order to fully understand these different chaotic transitions we reveal underlying global bifurcations and we show how they are connected to codimension-2 bifurcation points. Unnested islands of period doublings appear to be generic and hence must be expected in a large class of dynamical systems

Topological Transitions for Lattice Bosons in a Magnetic Field

We study the Hall response of the Bose-Hubbard model subjected to a magnetic field. We show that the Hall conductivity is proportional to the particle density plus an integer. The phase diagram is intersected by topological transitions between different integer values. These transitions originate from points in the phase diagram with effective charge conjugation symmetry, and are attributed to degeneracies in the many body spectrum which serve as sources for the Berry curvature. We find that extensive regions in the phase diagram exhibit a negative Hall conductivity, implying that flux flow is reversed in these regions - vortices there flow upstream. We discuss experimental implications of our findings.Comment: 11 pages, 7 figure

A Semi-analytic Study of Axial Perturbations of Ultra Compact Stars

Compact object perturbations, at linear order, often lead in solving one or more coupled wave equations. The study of these equations was typically done by numerical or semi-analytical methods. The WKB method and the associated Bohr-Sommerfeld rule have been proved extremely useful tools in the study of black-hole perturbations and the estimation of the related quasi-normal modes. Here we present an extension of the aforementioned semi-analytic methods in the study of perturbations of ultra-compact stars and gravastars.Comment: Accepted for publication in CQG, 13 pages, 3 figures, 5 table