Sex and recombination in the H\"otzel aging model

Why sex evolved and it prevails in nature remains one of the great puzzles of evolution. Most biologists would explain that it promotes genetic variability, however this explanation suffers from several difficulties. What advantages might sex confer? The present communication aims at certain investigations related to this question, in this way we introduce sexual recombination on the H\"otzel model (with males and females) and we compare these results with those from asexual reproduction without recombination.Comment: 10 pages, 6 figure

Interfacial confinement in core-shell nanowires due to high dielectric mismatch

We theoretically investigate the role of the dielectric mismatch between materials on the energy levels and recombination energies of a core-shell nanowire. Our results demonstrate that when the dielectric constant of the core material is lower than that of the shell material, the self-image potential pushes the charge carriers towards the core-shell interface, in such a way that the ideal confinement model is no longer suitable. The effects of this interfacial confinement on the electronic properties of such wires, as well as on its response to applied magnetic fields, are discussed.Comment: 4 pages, 3 figures and 1 material Supplementary; Applied Physics Letters 201

The Atwood's machine as a tool to introduce variable mass systems

This paper discusses an instructional strategy which explores eventual similarities and/or analogies between familiar problems and more sophisticated systems. In this context, the Atwood's machine problem is used to introduce students to more complex problems involving ropes and chains. The methodology proposed helps students to develop the ability needed to apply relevant concepts in situations not previously encountered. The pedagogical advantages are relevant for both secondary and high school students, showing that, through adequate examples, the question of the validity of Newton's second law may be introduced to even beginning students.Comment: Accepted for publication in Physics Educatio

Phase transition in hierarchy model of Bonabeau et al

The model of Bonabeau explains the emergence of social hierarchies from the memory of fights in an initially egalitarian society. Introducing a feedback from the social inequality into the probability to win a fight, we find a sharp transition between egalitarian society at low population density and hierarchical society at high population density.Comment: 3 pages including two figs.; for Int. J. Mod. Phys.

Black Holes in 2+1 Teleparallel Theories of Gravity

We apply the Hamiltonian formulation of teleparallel theories of gravity in 2+1 dimensions to a circularly symmetric geometry. We find a family of one-parameter black hole solutions. The BTZ solution fixes the unique free parameter of the theory. The resulting field equations coincide with the teleparallel equivalent of Einstein's three-dimensional equations. We calculate the gravitational energy of the black holes by means of the simple expression that arises in the Hamiltonian formulation and conclude that the resulting value is identical to that calculated by means of the Brown-York method.Comment: 20 pages, Latex file, no figure

Baryon and Antibaryon production at RHIC energies in the Dual Parton Model

We compute the mid-rapidity densities of pions, kaons, baryons and antibaryons in $Au$--$Au$ collisions at $\sqrt{s}$ = 130 GeV in the Dual Parton Model supplemented with final state interactions, and we present a comparison with available data.Comment: 4 pages, 2 figures. Talk given at XXXVII Rencontres de Moriond, Les Arcs, France, March 200

Self-organizing social hierarchies on scale-free networks

In this work we extend the model of Bonabeau et al. in the case of scale-free networks. A sharp transition is observed from an egalitarian to an hierarchical society, with a very low population density threshold. The exact threshold value also depends on the network size. We find that in an hierarchical society the number of individuals with strong winning attitude is much lower than the number of the community members that have a low winning probability