Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Covering graphs, magnetic spectral gaps and applications to polymers and
  nanoribbons
34
The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
17
The categories of this paper are: q-fin
24
The categories of this paper are: dg-ga
19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th