Scattering and bound states of a spin-1/2 neutral particle in the cosmic string spacetime

Abstract

In this paper the relativistic quantum dynamics of a spin-1/2 neutral particle with a magnetic moment 𝜇 in the cosmic string spacetime is reexamined by applying the von Neumann theory of self-adjoint extensions. Contrary to previous studies where the interaction between the spin and the line of charge is neglected, here we consider its effects. This interaction gives rise to a point interaction: ∇⋅ E = (2𝜆/𝛼)𝛿(𝑟)/𝑟. Due to the presence of the Dirac delta function, by applying an appropriated boundary condition provided by the theory of self-adjoint extensions, irregular solutions for the Hamiltonian are allowed. We address the scattering problem obtaining the phase shift, 𝑆-matrix, and the scattering amplitude. The scattering amplitude obtained shows a dependency with energy which stems from the fact that the helicity is not conserved in this system. Examining the poles of the 𝑆-matrix we obtain an expression for the bound states.The presence of bound states for this system has not been discussed before in the literature.