Critical wave-packet dynamics in the power-law bond disordered Anderson Model

We investigate the wave-packet dynamics of the power-law bond disordered one-dimensional Anderson model with hopping amplitudes decreasing as $H_{nm}\propto |n-m|^{-\alpha}$. We consider the critical case ($\alpha=1$). Using an exact diagonalization scheme on finite chains, we compute the participation moments of all stationary energy eigenstates as well as the spreading of an initially localized wave-packet. The eigenstates multifractality is characterized by the set of fractal dimensions of the participation moments. The wave-packet shows a diffusive-like spread developing a power-law tail and achieves a stationary non-uniform profile after reflecting at the chain boundaries. As a consequence, the time-dependent participation moments exhibit two distinct scaling regimes. We formulate a finite-size scaling hypothesis for the participation moments relating their scaling exponents to the ones governing the return probability and wave-function power-law decays

Delocalization in harmonic chains with long-range correlated random masses

We study the nature of collective excitations in harmonic chains with masses exhibiting long-range correlated disorder with power spectrum proportional to $1/k^{\alpha}$, where $k$ is the wave-vector of the modulations on the random masses landscape. Using a transfer matrix method and exact diagonalization, we compute the localization length and participation ratio of eigenmodes within the band of allowed energies. We find extended vibrational modes in the low-energy region for $\alpha > 1$. In order to study the time evolution of an initially localized energy input, we calculate the second moment $M_2(t)$ of the energy spatial distribution. We show that $M_2(t)$, besides being dependent of the specific initial excitation and exhibiting an anomalous diffusion for weakly correlated disorder, assumes a ballistic spread in the regime $\alpha>1$ due to the presence of extended vibrational modes.Comment: 6 pages, 9 figure

Avaliação de produtividade de grãos no desenvolvimento de cultivares de arroz irrigado para a região subtropical brasileira.

O objetivo do trabalho foi quantificar os efeitos desse procedimento no desempenho das linhagens selecionadas em gerações avançadas

Four dimensional "old minimal" N=2 supersymmetrization of R^4

We write in superspace the lagrangian containing the fourth power of the Weyl tensor in the "old minimal" d=4, N=2 supergravity, without local SO(2) symmetry. Using gauge completion, we analyze the lagrangian in components. We find out that the auxiliary fields which belong to the Weyl and compensating vector multiplets have derivative terms and therefore cannot be eliminated on-shell. Only the auxiliary fields which belong to the compensating nonlinear multiplet do not get derivatives and could still be eliminated; we check that this is possible in the leading terms of the lagrangian. We compare this result to the similar one of "old minimal" N=1 supergravity and we comment on possible generalizations to other versions of N=1,2 supergravity.Comment: 31 pages, no figures. Minor corrections. Details of the full calculation included as an appendix. Reference adde

Magnon delocalization in ferromagnetic chains with long-range correlated disorder

We study one-magnon excitations in a random ferromagnetic Heisenberg chain with long-range correlations in the coupling constant distribution. By employing an exact diagonalization procedure, we compute the localization length of all one-magnon states within the band of allowed energies $E$. The random distribution of coupling constants was assumed to have a power spectrum decaying as $S(k)\propto 1/k^{\alpha}$. We found that for $\alpha < 1$, one-magnon excitations remain exponentially localized with the localization length $\xi$ diverging as 1/E. For $\alpha = 1$ a faster divergence of $\xi$ is obtained. For any $\alpha > 1$, a phase of delocalized magnons emerges at the bottom of the band. We characterize the scaling behavior of the localization length on all regimes and relate it with the scaling properties of the long-range correlated exchange coupling distribution.Comment: 7 Pages, 5 figures, to appear in Phys. Rev.

Reflectância de um vinhedo irrigado no Submédio do Vale do São Francisco.

Este trabalho teve como objetivo determinar os valores de reflectância média diária durante um ciclo produtivo da videira. Para tanto, foi conduzido um experimento em uma área comercial da Fazenda Ouro Verde, município de Casa Nova-BA, no qual foi utilizada a variedade Syrah. Para a determinação da reflectância, foram utilizados três piranômetros, sendo um para medir radiação global incidente (Rgi) e dois instalados de maneira invertida, com o sensor voltado para a superfície, para medir a radiação refletida (Rgr). Posteriormente, com base nestes dados, a refletância foi obtida por meio da relação entre os valores da radiação solar refletida (Rgr) e incidente (Rgi). Observou-se que os valores horários da reflectância estiveram relacionados ao ângulo de elevação solar. Durante o ciclo produtivo da videira oscilou de 24% à 15%, com valores médios diários em torno de 19%. Estes dados podem ser utilizados como parâmetros de entrada em modelos de simulação climática