Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: A characterization of causal automorphisms by wave equations
3
The categories of this paper are: physics
16
The categories of this paper are: stat
6
The categories of this paper are: astro-ph
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex