Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Non Parallels Electric and Magnetic Fields in a F.R.W. Cosmology.
  Classical and Quantum Gravitational Implications   At first, we discuss parallels electric and magnetic fields solutions in a
gravitational background. Then, considering eletromagnetic and gravitational
waves symmetries we show a particular solution for stationary gravitational
waves. Finally we consider gravitation as a gauge theory (effective
gravitational theory), evaluate the propagators of the model, analyze the
corresponding quantum excitations and verify (confirm) the tree-level unitarity
at many places of the model.

20
The categories of this paper are: acc-phys
1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
16
The categories of this paper are: stat
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
24
The categories of this paper are: dg-ga
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat