Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: An axis-free overset grid in spherical polar coordinates for simulating
  3D self-gravitating flows
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
36
The categories of this paper are: cmp-lg
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
20
The categories of this paper are: acc-phys
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga
25
The categories of this paper are: patt-sol
17
The categories of this paper are: q-fin