Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stationary states of an electron in periodic structures in a constant
  uniform electrical field   On the basis of the transfer matrix technique an analytical method to
investigate the stationary states, for an electron in one-dimensional periodic
structures in an external electrical field, displaying the symmetry of the
problem is developed. These solutions are shown to be current-carrying. It is
also shown that the electron spectrum for infinite structures is continuous,
and the corresponding wave functions do not satisfy the symmetry condition of
the problem.

7
The categories of this paper are: hep-th
13
The categories of this paper are: quant-ph
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph
16
The categories of this paper are: stat
26
The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
2
The categories of this paper are: math