Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On semi-global invariants for focus-focus singularities   This article gives a classification, up to symplectic equivalence, of
singular Lagrangian foliations given by a completely integrable system of a
4-dimensional symplectic manifold, in a full neighbourhood of a singular leaf
of focus-focus (=nodal) type.

20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
24
The categories of this paper are: dg-ga
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn