Neumann-like integrable models

A countable class of integrable dynamical systems, with four dimensional phase space and conserved quantities in involution (H\_n,I\_n) are exhibited. For $n=1$ we recover Neumann sytem on T*S^2. All these systems are also integrable at the quantum level.Comment: 8 pages; latex2e;no figure. To appear in Physics Letters

Triangular buckling patterns of twisted inextensible strips

When twisting a strip of paper or acetate under high longitudinal tension, one observes, at some critical load, a buckling of the strip into a regular triangular pattern. Very similar triangular facets have recently been observed in solutions to a new set of geometrically-exact equations describing the equilibrium shape of thin inextensible elastic strips. Here we formulate a modified boundary-value problem for these equations and construct post-buckling solutions in good agreement with the observed pattern in twisted strips. We also study the force-extension and moment-twist behaviour of these strips by varying the mode number n of triangular facets

Clebsch (String) Parameterization of 3-Vectors and Their Actions

We discuss some properties of the intrinsically nonlinear Clebsch decomposition of a vector field into three scalars in d=3. In particular, we note and account for the incompleteness of this parameterization when attempting to use it in variational principles involving Maxwell and Chern-Simons actions. Similarities with string decomposition of metrics and their actions are also pointed out.Comment: 4 pages, LaTeX; email correspondence to [email protected]

Caracterização de raças de Pyrenophora tritici-repentis, agente etiológico da mancha amarela do trigo, no sul do Brasil.

bitstream/CNPT-2010/40333/1/p-bp60.pd

Ultrafast control of inelastic tunneling in a double semiconductor quantum

In a semiconductor-based double quantum well (QW) coupled to a degree of freedom with an internal dynamics, we demonstrate that the electronic motion is controllable within femtoseconds by applying appropriately shaped electromagnetic pulses. In particular, we consider a pulse-driven AlxGa1-xAs based symmetric double QW coupled to uniformly distributed or localized vibrational modes and present analytical results for the lowest two levels. These predictions are assessed and generalized by full-fledged numerical simulations showing that localization and time-stabilization of the driven electron dynamics is indeed possible under the conditions identified here, even with a simultaneous excitations of vibrational modes.Comment: to be published in Appl.Phys.Let

Colonização micorrízica em Araucaria Angustifolia sob condições naturais : aspectos metodológicos e influência da comunidade vegetal

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Zum Gedächtniss an Julius Plücker

Ausführliche Würdigung des mathematischen Wirkens Julius Plückers und eine knappe Darstellung der physikalischen Arbeiten. Enthält auch ein Schriftenverzeichnis Plückers