Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hopf Algebras and Congruence Subgroups   We prove that the kernel of the natural action of the modular group on the
center of the Drinfel'd double of a semisimple Hopf algebra is a congruence
subgroup. To do this, we introduce a class of generalized Frobenius-Schur
indicators and endow it with an action of the modular group that is compatible
with the original one.

24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
20
The categories of this paper are: acc-phys
28
The categories of this paper are: alg-geom
4
The categories of this paper are: cond-mat
1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph