Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Projective invariants of linear 3-webs and Gronwall's Conjecture   We present a projectively invariant description of planar linear 3-webs. For
a non-hexagonal 3-web, we introduce family of projective torsion-free Cartan
connections, the web leaves being geodesics for each member of the family, and
give a web linearization criterion. Finally, we propose an algorithm for
resolving the Gronwall conjecture and illustrate this approach by proving the
conjecture for 3-webs whose 2 foliations are 2 pencils of lines.

10
The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
27
The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph
6
The categories of this paper are: astro-ph
22
The categories of this paper are: chao-dyn
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
28
The categories of this paper are: alg-geom
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The categories of this paper are: acc-phys
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The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int
16
The categories of this paper are: stat
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The categories of this paper are: dg-ga
37
The categories of this paper are: supr-con
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The categories of this paper are: hep-th