Stable spatiotemporal solitons in Bessel optical lattices
  We investigate the existence and stability of three-dimensional (3D) solitons supported by cylindrical Bessel lattices (BLs) in self-focusing media. If the lattice strength exceeds a threshold value, we show numerically, and using the variational approximation, that the solitons are stable within one or two intervals of values of their norm. In the latter case, the Hamiltonian-vs.-norm diagram has a "swallowtail" shape, with three cuspidal points. The model applies to Bose-Einstein condensates (BECs) and to optical media with saturable nonlinearity, suggesting new ways of making stable 3D BEC solitons and "light bullets" of an arbitrary size. 
D. Mihalache, D. Mazilu, F. Lederer, B. A. Malomed, Y. V. Kartashov,   L.-C. Crasovan, and L. Torner