On the random neighbor Olami-Feder-Christensen slip-stick model

We reconsider the treatment of Lise and Jensen (Phys. Rev. Lett. 76, 2326 (1996)) on the random neighbor Olami-Feder-Christensen stik-slip model, and examine the strong dependence of the results on the approximations used for the distribution of states p(E).Comment: 6pages, 3 figures. To be published in PRE as a brief repor

On the robustness of scale invariance in SOC models

A random neighbor extremal stick-slip model is introduced. In the thermodynamic limit, the distribution of states has a simple analytical form and the mean avalanche size, as a function of the coupling parameter, is exactly calculable. The system is critical only at a special point Jc in the coupling parameter space. However, the critical region around this point, where approximate scale invariance holds, is very large, suggesting a mechanism for explaining the ubiquity of scale invariance in Nature.Comment: 6 pages, 4 figures; submitted to Physical Review E; http://link.aps.org/doi/10.1103/PhysRevE.59.496

Superscars in the LiNC=LiCN isomerization reaction

We demonstrate the existence of superscarring in the LiNC=LiCN isomerization reaction described by a realistic potential interaction in the range of readily attainable experimental energies. This phenomenon arises as the effect of two periodic orbits appearing "out of the blue"in a saddle--node bifurcation taking place in the dynamics of the system. Potential practical consequences of this superlocalization in the corresponding wave functions are also considered.Comment: 6 pages, 5 figures. to appear in EP

Estratégia de sobrevivência de panicum maximum tanzânia sob pastejo rotacionado.

Foi avaliada a dinâmica de perfilhamento do capim-tanzânia ao longo de um ano, visando caracterizar sua estratégia de sobrevivência em 5 touceiras. As maiores taxas de natalidade ocorreram em janeiro (76,6 p.100) e março (51,3 p.100) e as menores em junho (19,7 p.100) e agosto (13,2 p.100). As maiores taxas de mortalidade ocorreram em janeiro (72,5 p.100) e março (55,2 p.100) e as menores em abril (28,8 p.100) a outubro (24,4 p.100). Houve florescimento quando o fotoperíodo foi inferior a 11,5 horas (abril-agosto), onde as taxas de natalidade foram menores devido à dominância apical. Entre janeiro e abril houve intensa renovação de perfilhos. Grande proporção de perfilhos da geração que surgiu em março sobreviveu durante o período seco. Portanto, nesta geração, devem ser aplicadas técnicas de manejo visando à perenidade do pasto

Orbital Magnetism in Ensembles of Parabolic Potentials

We study the magnetic susceptibility of an ensemble of non-interacting electrons confined by parabolic potentials and subjected to a perpendicular magnetic field at finite temperatures. We show that the behavior of the average susceptibility is qualitatively different from that of billiards. When averaged over the Fermi energy the susceptibility exhibits a large paramagnetic response only at certain special field values, corresponding to comensurate classical frequencies, being negligible elsewhere. We derive approximate analytical formulae for the susceptibility and compare the results with numerical calculations.Comment: 4 pages, 4 figures, REVTE

Heat kernel of integrable billiards in a magnetic field

We present analytical methods to calculate the magnetic response of non-interacting electrons constrained to a domain with boundaries and submitted to a uniform magnetic field. Two different methods of calculation are considered - one involving the large energy asymptotic expansion of the resolvent (Stewartson-Waechter method) is applicable to the case of separable systems, and another based on the small time asymptotic behaviour of the heat kernel (Balian-Bloch method). Both methods are in agreement with each other but differ from the result obtained previously by Robnik. Finally, the Balian-Bloch multiple scattering expansion is studied and the extension of our results to other geometries is discussed.Comment: 13 pages, Revte

Padrão de crescimento populacional dos perfilhos de Panicum maximum cv. Tanzânia.

Disponível em: http://www.usp.br/siicusp/11osiicusp/index.htm. Acesso em: 10 de dez. 2003