Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Ab initio investigation of Elliott-Yafet electron-phonon mechanism in
  laser-induced ultrafast demagnetization
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph
19
The categories of this paper are: eess
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph
28
The categories of this paper are: alg-geom
1
The categories of this paper are: cs
3
The categories of this paper are: physics