This paper has been withdrawn by the author. Instead, more comprehensive and accurate works are placed in: 1) cond-mat/0610767: Universality in nonadiabatic behaviour of classical actions in nonlinear models with separatrix crossings, to appear in Phys.Rev.E; and 2) nlin/0611007: Change in the adiabatic invariant in a nonlinear two-mode model of Feshbach resonance passage, to appear in Physica D
@article{arxiv.nlin/0410040,
title = {Tunneling of Bose-Einstein condensates and nonlinear models with separatrix crossings},
author = {A. P. Itin},
journal= {arXiv preprint arXiv:nlin/0410040},
year = {2007}
}