Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Quadratic Irrationals, Closed Geodesics on the Modular Surface and
  Dynamical Zeta Functions   We show that generating functions associated to the sequence of convergents
of a quadratic irrational are related in a natural way to the dynam- ical zeta
function of a hyperbolic automorphism of the 2-torus. As a corollary, this
shows that the L\'evy constant of a quadratic irrational appears naturally as
the topological entropy of such maps.

10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
34
The categories of this paper are: chem-ph
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
3
The categories of this paper are: physics
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
32
The categories of this paper are: atom-ph