Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: A priori estimates for the motion of charged liquid drop: A dynamic
  approach via free boundary Euler equations
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org
10
The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
0
The categories of this paper are: hep-ph
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics