Relativistic Quantum Dynamics on a Double Cone
  In this paper, we study the relativistic quantum problem of a particle constrained to a double cone surface. For this purpose, we build the Dirac equation in a curved space using the tetrads formalism. Two cases are analysed. First, we consider a free particle on a double cone surface, and then we add an uniform magnetic field. The energy spectrum is obtained and the instability of the motion is discussed. We show that the magnetic field breaks the nappe degeneracy, inducing different energy spectra for each nappe. The results obtained here can be applied, for instance, in he investigation of the electronic and transport properties of condensed matter systems that can be described by an effective Dirac equation, such as graphene and topological insulators. 
Felipe Gomes, Edilberto Silva, Jonas Lima, Cleverson Filgueiras and   Fernando Moraes
quant-ph