Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Instantaneous versus non-instantaneous approach to relativistic
  ionization of atomic hydrogen by electron impact   We present a theoretical model for atomic hydrogen ionization by electron
impact in the instantaneous approximation and the more accurate
non-instantaneous approach using the methods of Quantum Electrodynamics, for
the binary coplanar and the coplanar asymmetric geometries. All electrons are
described by plane wave functions in the coplanar binary geometry but in the
asymmetric geometry the ejected electron is described by a Sommerfeld-Maue wave
function. It is shown that the two models give the same results in the non
relativistic limit for the binary coplanar geometry where the interactions can
be treated as instantaneous. However, this is no longer true for the
relativistic case where one has to take into account both the instantaneous
interaction and the radiation interaction. These results are obtained in the
first order of perturbation theory.

1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
13
The categories of this paper are: quant-ph
7
The categories of this paper are: hep-th
17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin