Surface crossover exponent for branched polymers in two dimensions

Transfer-matrix methods on finite-width strips with free boundary conditions are applied to lattice site animals, which provide a model for randomly branched polymers in a good solvent. By assigning a distinct fugacity to sites along the strip edges, critical properties at the special (adsorption) and ordinary transitions are assessed. The crossover exponent at the adsorption point is estimated as $\phi = 0.505 \pm 0.015$, consistent with recent predictions that $\phi = 1/2$ exactly for all space dimensionalities.Comment: 10 pages, LaTeX with Institute of Physics macros, to appear in Journal of Physics

Logarithmic corrections to gap scaling in random-bond Ising strips

Numerical results for the first gap of the Lyapunov spectrum of the self-dual random-bond Ising model on strips are analysed. It is shown that finite-width corrections can be fitted very well by an inverse logarithmic form, predicted to hold when the Hamiltonian contains a marginal operator.Comment: LaTeX code with Institute of Physics macros for 7 pages, plus 2 Postscript figures; to appear in Journal of Physics A (Letter to the Editor

Primeiro registro da família Tachinidae como parasitóide de psilídeo (Hemiptera: Psylloidea).

Resumo

Diversity and distribution of jumping plant-lice (Hemiptera: Psylloidea) along edges of Amazon - Cerrado transitional forests in Sorriso, Mato Grosso, Brazil.

Little is known about the jumping plant-lice of Brazil from where seven families, 45 genera and 76 species have been previously reported, but estimates suggest that there may be as many as 1,000 species. This study reports 34 species of Psylloidea which were collected along the edges of Amazon?Cerrado natural transitional forests in the municipality of Sorriso, state of Mato Grosso, from August 2013 to July 2014. Of the species reported in this study only nine represent described taxa, two of which are reported for the first time from Mato Grosso.hardt et al. 2013; Mazzardo 2014; Mazzardo et al. 2016): the two introduced eucalypt pests Blastopsylla occidentalis and Glycaspis brimblecombei, the three Fabaceae feeders Euphalerus clitoriae, Isogonoceraia divergipennis and Macrocorsa beeryi, the Toona pest Mastigimas anjosi, and the Nectandra psylloid Limataphalara lautereri. To improve the apparent lack of knowledge, a survey of the psylloid fauna of the edges of Amazon?Cerrado native transitional forests was conducted in Sorriso, Mato Grosso, Brazil. Here we present a commented inventory of the species encountered during the dry and rainy seasons

Smoothly-varying hopping rates in driven flow with exclusion

We consider the one-dimensional totally asymmetric simple exclusion process (TASEP) with position-dependent hopping rates. The problem is solved,in a mean field/adiabatic approximation, for a general (smooth) form of spatial rate variation. Numerical simulations of systems with hopping rates varying linearly against position (constant rate gradient), for both periodic and open boundary conditions, provide detailed confirmation of theoretical predictions, concerning steady-state average density profiles and currents, as well as open-system phase boundaries, to excellent numerical accuracy.Comment: RevTeX 4.1, 14 pages, 9 figures (published version

New Insights for Benefit of Legume Inclusion in Grazing Systems

The benefits and challenges of legume inclusion in grazing systems have been well documented over time and across different regions. Recent investigations have provided novel insights into the benefits of legume inclusion in grazing systems. Our objective is not to provide a wide overview of the benefits of legume inclusion but to explore novel insights of recent advancements made from studies evaluating legume inclusion in grazing systems. Efficiency of resource use through legume inclusion in grazing systems can reduce the water footprint associated with beef production through improvements in forage nutritive value and animal performance. These efficiencies also translate into improvements in nutrient cycling and nutrient transfer, which are critical for sustaining productivity of grazing systems. Moreover, evidence exists highlighting the importance of root contact between grasses and legumes for sharing N. Provisioning of floral resources from legumes has also been shown to be important for providing habitat for pollinator species. Lastly, soil microbial abundance of microorganisms associated with N2 fixation can be altered according to species present within a pasture, especially when legumes are present. Insights derived from such recent studies continue to provide evidence for the need to continue to develop legume-based grazing agroecosystems

Finite Size Scaling of the 2D Six-Clock model

We investigate the isotropic-anisotropic phase transition of the two-dimensional XY model with six-fold anisotropy, using Monte Carlo renormalization group method. The result indicates difficulty of observing asymptotic critical behavior in Monte Carlo simulations, owing to the marginal flow at the fixed point.Comment: Short note. revtex, 6 pages, 3 figures. To appear in J. Phys. Soc. Jpn. Vol.70 No. 2 (Feb 2001

On surface properties of two-dimensional percolation clusters

The two-dimensional site percolation problem is studied by transfer-matrix methods on finite-width strips with free boundary conditions. The relationship between correlation-length amplitudes and critical indices, predicted by conformal invariance, allows a very precise determination of the surface decay-of-correlations exponent, $\eta_s = 0.6664 \pm 0.0008$, consistent with the analytical value $\eta_s = 2/3$. It is found that a special transition does not occur in the case, corroborating earlier series results. At the ordinary transition, numerical estimates are consistent with the exact value $y_s = -1$ for the irrelevant exponent.Comment: 8 pages, LaTeX with Institute of Physics macros, to appear in Journal of Physics

Anomalous dynamics in two- and three- dimensional Heisenberg-Mattis spin glasses

We investigate the spectral and localization properties of unmagnetized Heisenberg-Mattis spin glasses, in space dimensionalities $d=2$ and 3, at T=0. We use numerical transfer-matrix methods combined with finite-size scaling to calculate Lyapunov exponents, and eigenvalue-counting theorems, coupled with Gaussian elimination algorithms, to evaluate densities of states. In $d=2$ we find that all states are localized, with the localization length diverging as $\omega^{-1}$, as energy $\omega \to 0$. Logarithmic corrections to density of states behave in accordance with theoretical predictions. In $d=3$ the density-of-states dependence on energy is the same as for spin waves in pure antiferromagnets, again in agreement with theoretical predictions, though the corresponding amplitudes differ.Comment: RevTeX4, 9 pages, 9 .eps figure

Kosterlitz-Thouless transition in three-state mixed Potts ferro-antiferromagnets

We study three-state Potts spins on a square lattice, in which all bonds are ferromagnetic along one of the lattice directions, and antiferromagnetic along the other. Numerical transfer-matrix are used, on infinite strips of width $L$ sites, $4 \leq L \leq 14$. Based on the analysis of the ratio of scaled mass gaps (inverse correlation lengths) and scaled domain-wall free energies, we provide strong evidence that a critical (Kosterlitz-Thouless) phase is present, whose upper limit is, in our best estimate, $T_c=0.29 \pm 0.01$. From analysis of the (extremely anisotropic) nature of excitations below $T_c$, we argue that the critical phase extends all the way down to T=0. While domain walls parallel to the ferromagnetic direction are soft for the whole extent of the critical phase, those along the antiferromagnetic direction seem to undergo a softening transition at a finite temperature. Assuming a bulk correlation length varying, for $T>T_c$, as $\xi (T) =a_\xi \exp [ b_\xi (T-T_c)^{-\sigma}]$, $\sigma \simeq 1/2$, we attempt finite-size scaling plots of our finite-width correlation lengths. Our best results are for $T_c=0.50 \pm 0.01$. We propose a scenario in which such inconsistency is attributed to the extreme narrowness of the critical region.Comment: 11 pages, 6 .eps figures, LaTeX with IoP macros, to be published in J Phys