Analytic Structure of the S-Matrix for Singular Quantum Mechanics
  The analytic structure of the S-matrix of singular quantum mechanics is examined within a multichannel framework, with primary focus on its dependence with respect to a parameter ($\Omega$) that determines the boundary conditions. Specifically, a characterization is given in terms of salient mathematical and physical properties governing its behavior. These properties involve unitarity and associated current-conserving Wronskian relations, time-reversal invariance, and Blaschke factorization. The approach leads to an interpretation of effective nonunitary solutions in singular quantum mechanics and their determination from the unitary family. 
Horacio E. Camblong, Luis N. Epele, Huner Fanchiotti, and Carlos A.   Garcia Canal
quant-ph hep-th math-ph math.MP