Multi-band structure of the quantum bound states for a generalized   nonlinear Schrodinger model
  By using the method of coordinate Bethe ansatz, we study N-body bound states of a generalized nonlinear Schrodinger model having two real coupling constants c and \eta. It is found that such bound states exist for all possible values of c and within several nonoverlapping ranges (called bands) of \eta. The ranges of \eta within each band can be determined completely using Farey sequences in number theory. We observe that N-body bound states appearing within each band can have both positive and negative values of the momentum and binding energy. 
B. Basu-Mallick (1), Tanaya Bhattacharyya (1), Diptiman Sen (2) ((1)   SINP, Kolkata, (2) IISc, Bangalore)