Persistence in the zero-temperature dynamics of the QQ-states Potts model on undirected-directed Barab\'asi-Albert networks and Erd\"os-R\'enyi random graphs

The zero-temperature Glauber dynamics is used to investigate the persistence probability $P(t)$ in the Potts model with $Q=3,4,5,7,9,12,24,64, 128$, $256, 512, 1024,4096,16384$,..., $2^{30}$ states on {\it directed} and {\it undirected} Barab\'asi-Albert networks and Erd\"os-R\'enyi random graphs. In this model it is found that $P(t)$ decays exponentially to zero in short times for {\it directed} and {\it undirected} Erd\"os-R\'enyi random graphs. For {\it directed} and {\it undirected} Barab\'asi-Albert networks, in contrast it decays exponentially to a constant value for long times, i.e, $P(\infty)$ is different from zero for all $Q$ values (here studied) from $Q=3,4,5,..., 2^{30}$; this shows "blocking" for all these $Q$ values. Except that for $Q=2^{30}$ in the {\it undirected} case $P(t)$ tends exponentially to zero; this could be just a finite-size effect since in the other "blocking" cases you may have only a few unchanged spins.Comment: 14 pages, 8 figures for IJM

Analysing and controlling the tax evasion dynamics via majority-vote model

Within the context of agent-based Monte-Carlo simulations, we study the well-known majority-vote model (MVM) with noise applied to tax evasion on simple square lattices, Voronoi-Delaunay random lattices, Barabasi-Albert networks, and Erd\"os-R\'enyi random graphs. In the order to analyse and to control the fluctuations for tax evasion in the economics model proposed by Zaklan, MVM is applied in the neighborhod of the noise critical $q_{c}$. The Zaklan model had been studied recently using the equilibrium Ising model. Here we show that the Zaklan model is robust and can be reproduced also through the nonequilibrium MVM on various topologies.Comment: 18 pages, 7 figures, LAWNP'09, 200

First record of Caliothrips phaseoli (Hood, 1912) (Thysanoptera: Thripidae) on Arachis spp. (Fabaceae) in Brazil.

The objective of this work was to establish the first record of Caliothrips phaseoli (Hood, 1912) (Thysanoptera: Thripidae); in forage peanut accessions in the state of Acre, Brazil. The specimens were collected directly from the leaves of infested plants grown in pots and under greenhouse conditions, preserved in 70 % ethyl alcohol, and mounted on slides to later be observed under a microscope. Caliothrips phaseoli is a polyphagous species considered an important pest in bean and soybean crops in Brazil. The insect feeds on forage peanuts causes chlorosis on the leaves and delays the development of infested plants, although no mortality was verified

Clustering, Angular Size and Dark Energy

The influence of dark matter inhomogeneities on the angular size-redshift test is investigated for a large class of flat cosmological models driven by dark energy plus a cold dark matter component (XCDM model). The results are presented in two steps. First, the mass inhomogeneities are modeled by a generalized Zeldovich-Kantowski-Dyer-Roeder (ZKDR) distance which is characterized by a smoothness parameter $\alpha(z)$ and a power index $\gamma$, and, second, we provide a statistical analysis to angular size data for a large sample of milliarcsecond compact radio sources. As a general result, we have found that the $\alpha$ parameter is totally unconstrained by this sample of angular diameter data.Comment: 9 pages, 7 figures, accepted in Physical Review

Numerical Simulation of Magnetic Interactions in Polycrystalline YFeO3

The magnetic behavior of polycrystalline yttrium orthoferrite was studied from the experimental and theoretical points of view. Magnetization measurements up to 170 kOe were carried out on a single-phase YFeO3 sample synthesized from heterobimetallic alkoxides. The complex interplay between weak-ferromagnetic and antiferromagnetic interactions, observed in the experimental M(H) curves, was successfully simulated by locally minimizing the magnetic energy of two interacting Fe sublattices. The resulting values of exchange field (H_E = 5590 kOe), anisotropy field (H_A = 0.5 kOe) and Dzyaloshinsky-Moriya antisymmetric field (H_D = 149 kOe) are in good agreement with previous reports on this system.Comment: 26 pages, 9 figure

Distribuição do sistema radicular da Mangueira CV. Palmer sob secamento parcial.

Nesse contexto o presente trabalho teve como objetivo avaliar o efeito do secamento parcial do sistema radicular sobre a distribuição do sistema radicular da mangueira cultivar Palmer nas condições semiáridas do norte de Minas Gerais. Os tratamentos foram instalados com base na redução de 50% da lamina bruta calculada, isto é aplicação de água em apenas um lado da fileira de plantas no tempo equivalente a aplicação nos dois lados e com base na fase fonológica da cultura. Os tratamentos ficaram da seguinte forma: T1- LB total na fase 1, redução de 50% com alternâncias de 7 dias nas demais fases; T2-LB total na fase 1, redução de 50% com alternâncias de 21 dias nas demais fases; e T3-redução de 50% da LB sem alternância, ou seja, com irrigação fixa em um só lado da fileira de plantas e T4-LB total em todas as fases (controle). Para as profundidades dos diferentes tratamentos não ocorreu diferença para o T1 (alternância de 7 dias) e o T4 (Controle). Já para as distâncias do caule houve diferença para todos os tratamentos