Chaotic Diffusion on Periodic Orbits: The Perturbed Arnol'd Cat Map

Chaotic diffusion on periodic orbits (POs) is studied for the perturbed Arnol'd cat map on a cylinder, in a range of perturbation parameters corresponding to an extended structural-stability regime of the system on the torus. The diffusion coefficient is calculated using the following PO formulas: (a) The curvature expansion of the Ruelle zeta function. (b) The average of the PO winding-number squared, $w^{2}$, weighted by a stability factor. (c) The uniform (nonweighted) average of $w^{2}$. The results from formulas (a) and (b) agree very well with those obtained by standard methods, for all the perturbation parameters considered. Formula (c) gives reasonably accurate results for sufficiently small parameters corresponding also to cases of a considerably nonuniform hyperbolicity. This is due to {\em uniformity sum rules} satisfied by the PO Lyapunov eigenvalues at {\em fixed} $w$. These sum rules follow from general arguments and are supported by much numerical evidence.Comment: 6 Tables, 2 Figures (postscript); To appear in Physical Review

Ensaio Nacional de aveias forrageiras 2009 - análise conjunta.

Com objetivo de avaliar a capacidade produtiva de forragem de genótipos de aveias brancas e pretas, foram conduzidos experimentos em oito locais do Brasil (Cruz Alta, Passo Fundo e Três de Maio no Rio Grande do Sul; Lages e Canoinhas em Santa Catarina; Londrina e Ponta Grossa no Paraná e São Carlos em São Paulo)

Magnetic Properties of Weakly Doped Antiferromagnets

We study the spin excitations and the transverse susceptibility of a two-dimensional antiferromagnet doped with a small concentration of holes in the t-J model. The motion of holes generates a renormalization of the magnetic properties. The Green's functions are calculated in the self-consistent Born approximation. It is shown that the long-wavelength spin waves are significantly softened and the shorter-wavelength spin waves become strongly damped as the doping increases. The spin wave velocity is reduced by the coherent motion of holes, and not increased as has been claimed elsewhere. The transverse susceptibility is found to increase considerably with doping, also as a result of coherent hole motion. Our results are in agreement with experimental data for the doped copper oxide superconductors.Comment: 20 page

Searches for Lepton Flavour Violation at a Linear Collider

We investigate the prospects for detection of lepton flavour violation in sparticle production and decays at a Linear Collider (LC), in models guided by neutrino oscillation data. We consider both slepton pair production and sleptons arising from the cascade decays of non-leptonic sparticles. We study the expected signals when lepton-flavour-violating (LFV) interactions are induced by renormalization effects in the Constrained Minimal Supersymmetric extension of the Standard Model (CMSSM), focusing on the subset of the supersymmetric parameter space that also leads to cosmologically interesting values of the relic neutralino LSP density. Emphasis is given to the complementarity between the LC, which is sensitive to mixing in both the left and right slepton sectors, and the LHC, which is sensitive primarily to mixing in the right sector. We also emphasize the complementarity between searches for rare LFV processes at the LC and in low-energy experiments.Comment: 19 pages, 10 figure