Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The strength of a pair of point vortices in an incompressible inviscid
  fluid in 3d can blow up in finite time   The evolution of a pair of point vortices in whole space, subject to the
inviscid Euler equations for incompressible fluid flow, is solved exactly for
rotationally symmetric initial conditions. This exact solution shows that the
vortex strength for a pair of point vortices can either remain stable or blow
up in finite time, depending on the initial data.

29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
18
The categories of this paper are: econ
13
The categories of this paper are: quant-ph
36
The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
16
The categories of this paper are: stat
26
The categories of this paper are: bayes-an
27
The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga