Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Causality violation in plane wave spacetimes   It is widely held that plane wave spacetimes are causally well behaved which
means that they are free from causal pathologies such as closed timelike curves
or closed null geodesics. In this paper, we show that one can get closed null
geodesics in a plane wave metric by analytically solving the geodesic
equations.

30
The categories of this paper are: q-alg
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math
18
The categories of this paper are: econ
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
36
The categories of this paper are: cmp-lg
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol