Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Metallic hydrogen with a strong electron-phonon interaction at a
  pressure of 300-500 GPa   Atomic metallic hydrogen with a lattice with FDDD symmetry is shown to have a
stable phase under hydrostatic compression in the range of pressure 350 - 500
GPa.

7
The categories of this paper are: hep-th
2
The categories of this paper are: math
17
The categories of this paper are: q-fin
21
The categories of this paper are: adap-org
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol
28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph