Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Euler - Heisenberg effective action and magnetoelectric effect in
  multilayer graphene
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
16
The categories of this paper are: stat
19
The categories of this paper are: eess
2
The categories of this paper are: math
20
The categories of this paper are: acc-phys
30
The categories of this paper are: q-alg
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
21
The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph
22
The categories of this paper are: chao-dyn
18
The categories of this paper are: econ