Recent advances and open challenges in percolation

Percolation is the paradigm for random connectivity and has been one of the most applied statistical models. With simple geometrical rules a transition is obtained which is related to magnetic models. This transition is, in all dimensions, one of the most robust continuous transitions known. We present a very brief overview of more than 60 years of work in this area and discuss several open questions for a variety of models, including classical, explosive, invasion, bootstrap, and correlated percolation

First-order transitions and triple point on a random p-spin interaction model

The effects of competing quadrupolar- and spin-glass orderings are investigated on a spin-1 Ising model with infinite-range random $p$-spin interactions. The model is studied through the replica approach and a phase diagram is obtained in the limit $p\to\infty$. The phase diagram, obtained within replica-symmetry breaking, exhibits a very unusual feature in magnetic models: three first-order transition lines meeting at a commom triple point, where all phases of the model coexist.Comment: 9 pages, 2 ps figures include

Two Kerr black holes with axisymmetric spins: An improved Newtonian model for the head-on collision and gravitational radiation

We present a semi-analytical approach to the interaction of two (originally) Kerr black holes through a head-on collision process. An expression for the rate of emission of gravitational radiation is derived from an exact solution to the Einstein's field equations. The total amount of gravitational radiation emitted in the process is calculated and compared to current numerical investigations. We find that the spin-spin interaction increases the emission of gravitational wave energy up to 0.2% of the total rest mass. We discuss also the possibility of spin-exchange between the holes.Comment: 8 pages, RevTeX, 2 figures, psbox macro include

Nonequilibrium Zaklan model on Apollonian Networks

The Zaklan model had been proposed and studied recently using the equilibrium Ising model on Square Lattices (SL) by Zaklan et al (2008), near the critica temperature of the Ising model presenting a well-defined phase transition; but on normal and modified Apollonian networks (ANs), Andrade et al. (2005, 2009) studied the equilibrium Ising model. They showed the equilibrium Ising model not to present on ANs a phase transition of the type for the 2D Ising model. Here, using agent-based Monte-Carlo simulations, we study the Zaklan model with the well-known majority-vote model (MVM) with noise and apply it to tax evasion on ANs, to show that differently from the Ising model the MVM on ANs presents a well defined phase transition. To control the tax evasion in the economics model proposed by Zaklan et al, MVM is applied in the neighborhood of the critical noise $q_{c}$ to the Zaklan model. Here we show that the Zaklan model is robust because this can be studied besides using equilibrium dynamics of Ising model also through the nonequilibrium MVM and on various topologies giving the same behavior regardless of dynamic or topology used here.Comment: 11 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1204.0386 and arXiv:0910.196

Optical limiting behavior of bismuth oxide-based glass in the visible range

The authors report experimental results on the optical limiting behavior of a bismuth oxide-based glass by exciting the samples with nanosecond laser pulses at 532 and 598 nm. The results show that two-photon and free-carrier absorption processes contribute for the nonlinear absorption. Values for β, the two-photon absorption coefficient, and σe, the absorption cross section due to free carriers, were determined. The values for β and σe are dependent on the amount of bismuth oxide in the glass composition

Caracterização da estrutura genética do pinhão manso (Jatropha curcas L.): isolamento de fragmentos de dna enriquecidos com sequências de microssatélites.

O pinhão manso (Jatropha curcas) é uma planta oleaginosa que vem se destacando por apresentar um alto potencial na produção de biocombustíveis. Por este motivo o interesse em sua exploração comercial vem aumentado consideravelmente. Assim, torna-se imprescindível o desenvolvimento de tecnologias moleculares de monitoramento e seleção de populações naturais e cultivares. Nesse contexto, marcadores moleculares como os microssatélites são amplamente utilizados. No entanto, os genomas de organismos eucariontes são muito amplos e, assim, o isolamento de seqüências de microssatélites específicas, que possam atuar como marcadores, torna-se uma tarefa complexa. O presente trabalho teve como objetivo estabelecer um protocolo para isolar fragmentos de DNA específicos contendo loci de microssatélites. Este procedimento tem por finalidade aumentar a incidência das seqüências alvo para futura clonagem. Foram testadas diferentes enzimas de restrição e sondas de DNA para o reconhecimento e captura de fragmentos contendo seqüências de microssatélites. Os resultados obtidos mostraram que a enzima RsaI apresentou o melhor padrão de digestão do DNA, enquanto as melhores sondas foram as compostas pelas repetições (AATG)6, (AAAC)6, (AATC)6 e (AAAG)6. Estes procedimentos constituem etapas fundamentais no processo de isolamento de microssatélites e contribuirão para a caracterização da estrutura genética do pinhão manso. Com isto, será possível avaliar quais os estoques mais adequados para seleção de linhagens viáveis para o cultivo, visando ganhos na produtividade

Quantum dot to disordered wire crossover: A complete solution in all length scales for systems with unitary symmetry

We present an exact solution of a supersymmetric nonlinear sigma model describing the crossover between a quantum dot and a disordered quantum wire with unitary symmetry. The system is coupled ideally to two electron reservoirs via perfectly conducting leads sustaining an arbitrary number of propagating channels. We obtain closed expressions for the first three moments of the conductance, the average shot-noise power and the average density of transmission eigenvalues. The results are complete in the sense that they are nonperturbative and are valid in all regimes and length scales. We recover several known results of the recent literature by taking particular limits.Comment: 4 page

The monoclinic phase of PZT ceramics: Raman and phenomenological theory studies

This work reports on the first Raman detection of the tetragonal to monoclinic phase transition in PZT ceramics near morphotropic phase boundary at low temperatures. The transition is characterized by changes in the frequency of lattice modes with the temperature. The results presented here confirm the previous one recently reported by Noheda et al. using high-resolution synchrotron X-ray powder diffraction technique and dielectric measurements. The stability of the new phase is discussed within the framework of phenomenological Landau-Devonshire Theory.Comment: 6 pages including 4 figures, Latex, submitted to Applied Physics Letter