Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Veech groups, irrational billiards and stable abelian differentials   We describe Veech groups of flat surfaces arising from irrational angled
polygonal billiards or irreducible stable abelian differentials. For irrational
polygonal billiards, we prove that these groups are non-discrete subgroups of
SO(2,R) and we calculate their rank.

1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
19
The categories of this paper are: eess
0
The categories of this paper are: hep-ph
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
24
The categories of this paper are: dg-ga
26
The categories of this paper are: bayes-an
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
10
The categories of this paper are: q-bio
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph