Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Classical and quantum dynamics of a charged scalar particle in a
  background of two counterpropagating plane waves   We consider a scalar particle in a background formed by two
counter-propagating plane waves. Two cases are studied: i) dynamics at a
magnetic node and ii) zero initial transverse canonical momentum. The Lorentz
and Klein-Gordon equations are solved for these cases and approximations
analysed. For the magnetic node solution (homogeneous, time-dependent electric
field), the modified Volkov wavefunction which arises from a high-energy
approximation is found to be inaccurate for all energies and the solution
itself unstable when photon emission (nonlinear Compton scattering) is
included. For the zero initial transverse canonical momentum case, in both
quantum and classical cases, forbidden parameter regimes, absent in the plane
wave model, are identified.

33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
4
The categories of this paper are: cond-mat
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
6
The categories of this paper are: astro-ph
2
The categories of this paper are: math
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org