Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Forward sum rule for the $2\gamma$-exchange correction to the charge
  radius extraction from elastic electron scattering
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
3
The categories of this paper are: physics
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
14
The categories of this paper are: math-ph
27
The categories of this paper are: comp-gas
10
The categories of this paper are: q-bio
31
The categories of this paper are: ao-sci
20
The categories of this paper are: acc-phys
13
The categories of this paper are: quant-ph
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
4
The categories of this paper are: cond-mat
5
The categories of this paper are: gr-qc