Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Motion of a circular cylinder and n point vortices in a perfect fluid   The paper studies the system of a rigid body interacting dynamically with
point vortices in a perfect fluid. For arbitrary value of vortex strengths and
circulation around the cylinder the system is shown to be Hamiltonian (the
corresponding Poisson bracket structure is rather complicated). We also reduced
the number of degrees of freedom of the system by two using the reduction by
symmetry technique and performed a thorough qualitative analysis of the
integrable system of a cylinder interacting with one vortex.

33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
5
The categories of this paper are: gr-qc
18
The categories of this paper are: econ
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
26
The categories of this paper are: bayes-an
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph
13
The categories of this paper are: quant-ph
1
The categories of this paper are: cs