Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First-order invariants of differential 2-forms   Let $M$ be a smooth manifold of dimension $2n$, and let $O_{M}$ be the dense
open subbundle in $\wedge^{2}T^{\ast}M$ of $2$-covectors of maximal rank. The
algebra of $\operatorname*{Diff}M$-invariant smooth functions of first order on
$O_{M}$ is proved to be isomorphic to the algebra of smooth
$Sp(\Omega_{x})$-invariant functions on $\wedge^{3}T_{x}^{\ast}M$, $x$ being a
fixed point in $M$, and $\Omega_{x}$ a fixed element in $(O_{M})_{x}$. The
maximum number of functionally independent invariants is computed.

37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
18
The categories of this paper are: econ
7
The categories of this paper are: hep-th
4
The categories of this paper are: cond-mat
17
The categories of this paper are: q-fin
0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
21
The categories of this paper are: adap-org
28
The categories of this paper are: alg-geom