Resolvent estimates for 2 dimensional perturbations of plane Couette Flow

We present results concerning resolvent estimates for the linear operator associated with the system of differential equations governing perturbations of the Couette flow. We prove estimates on the L_2 norm of the resolvent of this operator showing this norm to be proportional to the Reynolds number R for a region of the unstable half plane. For the remaining region, we show that the problem can be reduced to estimating the solution of a homogeneous ordinary differential equation with non-homogeneous boundary conditions. Numerical approximations indicate that the norm of the resolvent is proportional to R in the whole region of interest.Comment: 16 pages, 4 figures. A mistake in the proof of Theorem 1 was corrected. The presentation was changed a little, and typos were correcte

Semiclassical back reaction around a cosmic dislocation

The energy-momentum vacuum average of a conformally coupled massless scalar field vibrating around a cosmic dislocation (a cosmic string with a dislocation along its axis) is taken as source of the linearized semiclassical Einstein equations. The solution up to first order in the Planck constant is derived. Motion of a test particle is then discussed, showing that under certain circumstances a helical-like dragging effect, with no classical analogue around the cosmic dislocation, is induced by back reaction.Comment: Published version, 4 pages, no figures, REVTeX4 fil

Estudo da dinâmica da floresta manejada no projeto de manejo florestal comunitário do PC Pedro Peixoto na Amazônia Ocidental.

Neste trabalho são apresentados resultados do estudo da dinâmica da floresta em um sistema de manejo florestal voltado para a pequena propriedade. O sistema prescreve ciclo de corte de 10 anos e taxa de corte de 10 m3.ha-1 e tração animal para o arraste. O crescimento da floresta de 1 m3.ha-1.ano-1 foi compatível com o ciclo e taxa de corte adotados. Os danos causados pela exploração representaram 5 % da área basal total, e a taxa de mortalidade quatro anos após a exploração foi 3,2 %