Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On Unconventional Electron Pairing In a Periodic Potential   On the assumption that two electrons with the same group velocity effectively
attract each other a simple model Hamiltonian is proposed to question the
existence of unconventional electron pairs formed by electrons in a strong
periodic potential.

20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org
24
The categories of this paper are: dg-ga
29
The categories of this paper are: funct-an