Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Analytic hypoellipticity in dimension two   A simple geometric condition is sufficient for analytic hypoellipticity of
sums of squares of two vector fields in ${\mathbb R}^2$. This condition is
proved to be necessary for generic vector fields and for various special cases,
and to be both necessary and sufficient for a closely related family of
operators.

7
The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom
6
The categories of this paper are: astro-ph
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
34
The categories of this paper are: chem-ph
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int