Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Catastrophe Theory, Petrov's Algebraic Classification and
  gravitation phase transitions   A close relationship is demonstrated between the catastrophe theory, Petrov's
algebraic classification of the gravitational fields and the theory of phase
transitions.

9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
27
The categories of this paper are: comp-gas
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat