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R. Bach

Publications and source records attributed to R. Bach.

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Quantum Mechanical Cumulant Dynamics near Stable Periodic Orbits in Phase Space: Application to the classical-like dynamics of quantum accelerator modes

We formulate a general method for the study of semiclassical-like dynamics in stable regions of a mixed phase-space, in order to theoretically study the dynamics of quantum accelerator modes. In the simplest case, this involves determining solutions, which are stable when constrained to remain pure-state Gaussian wavepackets, and then propagating them using a cumulant-based formalism. Using this methodology, we study the relative longevity, under different parameter regimes, of quantum accelerator modes. Within this attractively simple formalism, we are able to obtain good qualitative agreement with exact wavefunction dynamics.

physics.atom-ph

Finite temperature oscillations of a Bose-Einstein condensate in a two-gas model

The temperature dependence of the frequencies of a Bose-Einstein condensate obtained in experiment has not been fully understood theoretically. In this paper we present a simplified version of a two-gas model. A numerically-found ground state of the system is used for the small-oscillations analysis. In the case of spherical symmetry a full spectrum of frequencies is found for low orbital quantum numbers. Avoided crossings that appear in the spectrum might be the reason for experimentally observed frequency shifts.

cond-mat