Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Contact reductions, mechanics and duality   Contact reduction is very closely related to symplectic reduction, but it
allows symmetries that are not manifest in Hamiltonian mechanics and moreover,
solution of the reduced problems yields solution of the original problem
without further integration.

22
The categories of this paper are: chao-dyn
32
The categories of this paper are: atom-ph
23
The categories of this paper are: solv-int
7
The categories of this paper are: hep-th
4
The categories of this paper are: cond-mat
16
The categories of this paper are: stat
5
The categories of this paper are: gr-qc
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
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
25
The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci