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

Plant population and spatial arrangement studies in the intercropping of maize and beans in Northeast Brazil.

In Northeast Brazil the peasant farmer use to raise their cropa in mixture, and the intercropping of maise and beans is very frequent.Paper for International Intercropping Workshop at ICRISAT, Hydederabad, India, from jannuary 10 at 13, 1979

Regeneração de algarobeiras em área de mata ciliar do rio de Contas, em Manoel Vitorino-BA.

O estudo teve como objetivo analisar a estrutura vegetal de áreas da Caatinga com a presença da algaroba

Sociabilidade de espécies invasoras em área de cultivo de manga na fazenda Boa Esperança, Petrolina-PE.

O presente trabalho teve por objetivo determinar o grau de afinidade entre as invasoras inventarias em área de cultivo de manga, na Fazenda Boa Esperança, em Petrolina-PE (09o09?W, 42o22?S)

Levantamento dos usos alternativos de espécies invasoras na região de Petrolina-PE.

O presente trabalho teve por objetivo identificar os usos alternativos das espécies invasoras pela comunidade local, principalmente na medicina popular. No período de maio a julho de 2000, 20 pessoas foram entrevistadas em cinco comunidades do município de Petrolina-PE, sendo perguntado inicialmente quais as principais plantas (invasoras ou nativas da caatinga) utilizadas na medicina caseira ou como forragem

Índice de associação entre espécies invasoras em áreas de cultivo de videira na vitivinícola Santa Maria, Lagoa Grande-PE.

O presente trabalho teve por objetivo determinar o grau de afinidade entre as invasoras inventariadas em área de cultivo de videira na Vitivinícola Santa Maria, município de Lagoa Grande-PE (09º00?S e 40º16?W)

Plano de manejo para espécies da Caatinga ameaçadas de extinção na Reserva Legal do Projeto Salitre.

Ecologia e distribuição das espécies; Myracrodruon urundeuva Allemão; Schinopsis brasiliensis Engler; Sideroxylon obtusifoliiium Roem & Schult; Amburana cearensis (Fr. Allem.) A. C. Smith; Causas do processo de extinção; Avaliação dos impactos causados pela ameaça de extinção da biodiversidade brasileira; Diagnóstico da situação das espécies; Ocorrência das quatro espécies em escala municipal; Situação das quatro espécies na área da Reserva Legal; Proposta para a conservação das espécies ameaçadas de extinção na Reserva Legal do Projeto Salitre, Juazeiro, BA; Estratégia para a implementação do plano de manejo das espécies estudadas.bitstream/item/54776/1/SDC243.pd

Irreversible magnetization under rotating fields and lock-in effect on ErBa_2Cu_3O_7 single crystal with columnar defects

We have measured the irreversible magnetization M_i of an ErBa_2Cu_3O_7 single crystal with columnar defects (CD), using a technique based on sample rotation under a fixed magnetic field H. This method is valid for samples whose magnetization vector remains perpendicular to the sample surface over a wide angle range - which is the case for platelets and thin films - and presents several advantages over measurements of M_L(H) loops at fixed angles. The resulting M_i(\Theta) curves for several temperatures show a peak in the CD direction at high fields. At lower fields, a very well defined plateau indicative of the vortex lock-in to the CD develops. The H dependence of the lock-in angle \phi_L follows the H^{-1} theoretical prediction, while the temperature dependence is in agreement with entropic smearing effects corresponding to short range vortex-defects interactions.Comment: 7 pages, 6 figures, to be published in Phys. Rev.

The anisotropic XY model on the inhomogeneous periodic chain

The static and dynamic properties of the anisotropic XY-model $(s=1/2)$ on the inhomogeneous periodic chain, composed of $N$ cells with $n$ different exchange interactions and magnetic moments, in a transverse field $h,$ are determined exactly at arbitrary temperatures. The properties are obtained by introducing the Jordan-Wigner fermionization and by reducing the problem to a diagonalization of a finite matrix of $nth$ order. The quantum transitions are determined exactly by analyzing, as a function of the field, the induced magnetization 1/n\sum_{m=1}^{n}\mu_{m}\left ($j$ denotes the cell, $m$ the site within the cell, $\mu_{m}$ the magnetic moment at site $m$ within the cell) and the spontaneous magnetization $1/n\sum_{m=1}^{n}\left< S_{j,m}^{x},\right>$ which is obtained from the correlations $\left< S_{j,m}^{x}S_{j+r,m}^{x}\right>$ for large spin separations. These results, which are obtained for infinite chains, correspond to an extension of the ones obtained by Tong and Zhong(\textit{Physica B} \textbf{304,}91 (2001)). The dynamic correlations, $\left< S_{j,m}^{z}(t)S_{j^{\prime},m^{\prime}}^{z}(0)\right>$, and the dynamic susceptibility, $\chi_{q}^{zz}(\omega),$ are also obtained at arbitrary temperatures. Explicit results are presented in the limit T=0, where the critical behaviour occurs, for the static susceptibility $\chi_{q}^{zz}(0)$ as a function of the transverse field $h$, and for the frequency dependency of dynamic susceptibility $\chi_{q}^{zz}(\omega)$.Comment: 33 pages, 13 figures, 01 table. Revised version (minor corrections) accepted for publiction in Phys. Rev.

Density-functionals not based on the electron gas: Local-density approximation for a Luttinger liquid

By shifting the reference system for the local-density approximation (LDA) from the electron gas to other model systems one obtains a new class of density functionals, which by design account for the correlations present in the chosen reference system. This strategy is illustrated by constructing an explicit LDA for the one-dimensional Hubbard model. While the traditional {\it ab initio} LDA is based on a Fermi liquid (the electron gas), this one is based on a Luttinger liquid. First applications to inhomogeneous Hubbard models, including one containing a localized impurity, are reported.Comment: 4 pages, 4 figures (final version, contains additional applications and discussion; accepted by Phys. Rev. Lett.