Bifurcation trees of Stark-Wannier ladders for accelerated BECs in an   optical lattice
  In this paper we show that in the semicassical regime of periodic potential large enough, the Stark-Wannier ladders become a dense energy spectrum because of a cascade of bifurcations while increasing the ratio between the effective nonlinearity strength and the tilt of the external field; this fact is associated to a transition from regular to quantum chaotic dynamics. The sequence of bifurcation points is explicitly given. 
Andrea Sacchetti
quant-ph nlin.CD