We investigate the dynamics of a Bose condensate, interacting with either repulsive or attractive forces, confined in a fully anisotropic harmonic potential. The (3 + 1)-dimensional Gross-Pitaevskii equation is integrated numerically to derive the collective excitation frequencies, showing a good agreement with those calculated with a variational technique. (C) 1998 Elsevier Science B.V

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The propagation of intense laser pulses through a four-level atomic system in a double-⌳ scheme is examined. Under conditions of adiabatic perturbation of the atomic quantum state, paired pulses with arbitrary shapes establish a correlation between their amplitudes and reach a quasiform-stable regime of propagation. The amplitude correlation is a feature of pulse matching, while the propagation presents the same properties as the so-called adiabatons, predicted and observed in single-⌳ systems. We show that in the double-⌳ scheme the phenomena of pulse matching and adiabaton-type propagation are associated with two distinct propagation normal modes.

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