Irreversible Opinion Spreading on Scale-Free Networks

We study the dynamical and critical behavior of a model for irreversible opinion spreading on Barab\'asi-Albert (BA) scale-free networks by performing extensive Monte Carlo simulations. The opinion spreading within an inhomogeneous society is investigated by means of the magnetic Eden model, a nonequilibrium kinetic model for the growth of binary mixtures in contact with a thermal bath. The deposition dynamics, which is studied as a function of the degree of the occupied sites, shows evidence for the leading role played by hubs in the growth process. Systems of finite size grow either ordered or disordered, depending on the temperature. By means of standard finite-size scaling procedures, the effective order-disorder phase transitions are found to persist in the thermodynamic limit. This critical behavior, however, is absent in related equilibrium spin systems such as the Ising model on BA scale-free networks, which in the thermodynamic limit only displays a ferromagnetic phase. The dependence of these results on the degree exponent is also discussed for the case of uncorrelated scale-free networks.Comment: 9 pages, 10 figures; added results and discussion on uncorrelated scale-free networks; added references. To appear in PR

Unintegrated parton distributions in nuclei

We study how unintegrated parton distributions in nuclei can be calculated from the corresponding integrated partons using the EPS09 parametrization. The role of nuclear effects is presented in terms of the ratio $R^A=\text{uPDF}^A/A\cdot \text{PDF}^N$ for both large and small $x$ domains.Comment: 9 pages, 4 figure

Geometric classical and total correlations via trace distance

We introduce the concepts of geometric classical and total correlations through Schatten 1-norm (trace norm), which is the only Schatten p-norm able to ensure a well-defined geometric measure of correlations. In particular, we derive the analytical expressions for the case of two-qubit Bell-diagonal states, discussing the superadditivity of geometric correlations. As an illustration, we compare our results with the entropic correlations, discussing both their hierarchy and monotonicity properties. Moreover, we apply the geometric correlations to investigate the ground state of spin chains in the thermodynamic limit. In contrast to the entropic quantifiers, we show that the classical correlation is the only source of 1-norm geometric correlation that is able to signaling an infinite-order quantum phase transition.Comment: v2: published versio

Integração de bases de dados de clima e de solos via serviços web.

A integração de dados agrícolas tem sido um grande desafio no desenvolvimento de aplicações para dar suporte à tomada de decisão no agronegócio. Entretanto esses dados estão dispersos em planilhas, relatórios técnicos, dissertações de mestrado, teses de doutorado, livros, boletins de pesquisa, além de meios magnéticos. Como não estão organizadas em um banco de dados único, as informações existentes não podem ser facilmente recuperadas e repassadas aos setores interessados. Este trabalho apresenta uma solução, baseada em serviços Web, para integração de dados de clima e de solos.Trabalho apresentado na V Mostra de Trabalhos de Estagiários e Bolsistas, Campinas, out. 2009

Does Good Mutation Help You Live Longer?

We study the dynamics of an age-structured population in which the life expectancy of an offspring may be mutated with respect to that of its parent. When advantageous mutation is favored, the average fitness of the population grows linearly with time $t$, while in the opposite case the average fitness is constant. For no mutational bias, the average fitness grows as t^{2/3}. The average age of the population remains finite in all cases and paradoxically is a decreasing function of the overall population fitness.Comment: 4 pages, 2 figures, RevTeX revised version, to appear in Phys. Rev. Let

Ising Ferromagnet: Zero-Temperature Dynamic Evolution

The dynamic evolution at zero temperature of a uniform Ising ferromagnet on a square lattice is followed by Monte Carlo computer simulations. The system always eventually reaches a final, absorbing state, which sometimes coincides with a ground state (all spins parallel), and sometimes does not (parallel stripes of spins up and down). We initiate here the numerical study of ``Chaotic Time Dependence'' (CTD) by seeing how much information about the final state is predictable from the randomly generated quenched initial state. CTD was originally proposed to explain how nonequilibrium spin glasses could manifest equilibrium pure state structure, but in simpler systems such as homogeneous ferromagnets it is closely related to long-term predictability and our results suggest that CTD might indeed occur in the infinite volume limit.Comment: 14 pages, Latex with 8 EPS figure