Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Some geometric structures of wave equations on manifolds of `neutral
  signatures'   In this paper, we study the symmetries and perform other geometric analyses
of the wave equation on some spacetimes {with non diagonal metric $g_{ij}$
which are of neutral signatures}. Wave equations on the standard Lorentzian
manifolds have been done but not on the manifolds from metrics of neutral
signatures.

1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
3
The categories of this paper are: physics
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
11
The categories of this paper are: hep-lat
18
The categories of this paper are: econ
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
25
The categories of this paper are: patt-sol
13
The categories of this paper are: quant-ph