The Network of Epicenters of the Olami-Feder-Christensen Model of Earthquakes

We study the dynamics of the Olami-Feder-Christensen (OFC) model of earthquakes, focusing on the behavior of sequences of epicenters regarded as a growing complex network. Besides making a detailed and quantitative study of the effects of the borders (the occurrence of epicenters is dominated by a strong border effect which does not scale with system size), we examine the degree distribution and the degree correlation of the graph. We detect sharp differences between the conservative and nonconservative regimes of the model. Removing border effects, the conservative regime exhibits a Poisson-like degree statistics and is uncorrelated, while the nonconservative has a broad power-law-like distribution of degrees (if the smallest events are ignored), which reproduces the observed behavior of real earthquakes. In this regime the graph has also a unusually strong degree correlation among the vertices with higher degree, which is the result of the existence of temporary attractors for the dynamics: as the system evolves, the epicenters concentrate increasingly on fewer sites, exhibiting strong synchronization, but eventually spread again over the lattice after a series of sufficiently large earthquakes. We propose an analytical description of the dynamics of this growing network, considering a Markov process network with hidden variables, which is able to account for the mentioned properties.Comment: 9 pages, 10 figures. Smaller number of figures, and minor text corrections and modifications. For version with full resolution images see http://fig.if.usp.br/~tpeixoto/cond-mat-0602244.pd

Divergência genética entre acessos de batata-doce utilizando descritores morfoagronômicos das raízes.

Objetivou-se caracterizar morfoagronômicamente 23 genótipos de batata-doce do banco ativo de germoplasma mantido na Embrapa Hortaliças; utilizar estas características para avaliar a variabilidade genética entre os materiais pela aplicação dos métodos de Análise por agrupamento hierárquico e análise por componentes principais e estimar parâmetros populacionais

Superdiffusion of massive particles induced by multi-scale velocity fields

We study drag-induced diffusion of massive particles in scale-free velocity fields, where superdiffusive behavior emerges due to the scale-free size distribution of the vortices of the underlying velocity field. The results show qualitative resemblance to what is observed in fluid systems, namely the diffusive exponent for the mean square separation of pairs of particles and the preferential concentration of the particles, both as a function of the response time.Comment: 5 pages, 5 figures. Accepted for publication in EP

Symmetry aspects of fermions coupled to torsion and electromagnetic fields

We study and explore the symmetry properties of fermions coupled to dynamical torsion and electromagnetic fields. The stability of the theory upon radiative corrections as well as the presence of anomalies are investigated.Comment: 9 pages, LaTe

Desempenho de cultivares de batata-doce no Distrito federal.

O presente trabalho teve como objetivo avaliar o desempenho agronômico de seis cultivares e três variedades de batata-doce nas condições edafoclimáticas no Recanto das Emas, DF

Desempenho de cultivares de batata-doce a partir mudas de alta qualidade fitossanitária em Ceilândia-DF.

O presente trabalho teve por objetivo avaliar o desempenho agronomico de oito cultivares utilizando mudas que passaram pela limpeza clonal. O experimento foi conduzido em condições de campo, no delineamento em blocos ao acaso com três repetições, em Ceilândia, DF.Suplemento. Edição dos Anais do 53 Congresso Brasileiro de Olericultura

Phases of quantum states in completely positive non-unitary evolution

We define an operational notion of phases in interferometry for a quantum system undergoing a completely positive non-unitary evolution. This definition is based on the concepts of quantum measurement theory. The suitable generalization of the Pancharatnan connection allows us to determine the dynamical and geometrical parts of the total phase between two states linked by a completely positive map. These results reduce to the knonw expressions of total, dynamical and geometrical phases for pure and mixed states evolving unitarily.Comment: 2 figure