Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dimers on graphs in non-orientable surfaces   The main result of this paper is a Pfaffian formula for the partition
function of the dimer model on a graph G embedded in a closed, possibly
non-orientable surface S. This formula is suitable for computational purposes,
and it is obtained using purely geometrical methods. The key step in the proof
consists of a correspondence between some orientations on G and the set of
pin^- structures on S. This generalizes (and simplifies) the results of a
previous paper [2].

10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc
13
The categories of this paper are: quant-ph
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
3
The categories of this paper are: physics
9
The categories of this paper are: nlin