Nonrelativistic quantum dynamics on a cone with and without a   constraining potential
  In this paper we investigate the bound state problem of nonrelativistic quantum particles on a conical surface. This kind of surface appears as a topological defect in ordinary semiconductors as well as in graphene sheets. Specifically, we compare and discuss the results stemming from two different approaches. In the first one, it is assumed that the charge carriers are bound to the surface by a constraining potential, while the second one is based on the Klein-Gordon type equation on surfaces, without the constraining potential. The main difference between both theories is the presence/absence of a potential which contains the mean curvature of a given surface. This fact changes the dependence of the bound states on the angular momentum $l$. Moreover, there are bound states that are absent in the Klein-Gordon theory, which instead appear in the Schr\"{o}dinger one. 
C. Filgueiras and E. O. Silva and F. M. Andrade
quant-ph hep-th math-ph math.MP