Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Energy-efficient spin injector into semiconductors driven by elastic
  waves
10
The categories of this paper are: q-bio
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
14
The categories of this paper are: math-ph
6
The categories of this paper are: astro-ph
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat