Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Gravitational potential energy of simple bodies: the method of negative
  density
4
The categories of this paper are: cond-mat
18
The categories of this paper are: econ
15
The categories of this paper are: nucl-ex
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
34
The categories of this paper are: chem-ph