Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Scattering and bound states of a spin--1/2 neutral particle in the
  cosmic string spacetime   In this paper the relativistic quantum dynamics of a spin-1/2 neutral
particle with a magnetic moment $\mu$ 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: $\boldsymbol{\nabla} \cdot \mathbf{E}=
(2\lambda/\alpha)\delta(r)/r$. 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.

30
The categories of this paper are: q-alg
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
20
The categories of this paper are: acc-phys
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
23
The categories of this paper are: solv-int
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
17
The categories of this paper are: q-fin
21
The categories of this paper are: adap-org