Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Observation of phonon structure in electron density of states of normal
  metal
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
35
The categories of this paper are: mtrl-th
2
The categories of this paper are: math
16
The categories of this paper are: stat
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs