Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Persistent Currents in Small, Imperfect Hubbard Rings   We have done a study with small, imperfect Hubbard rings with exact
diagonalization. The results for few-electron rings show, that the
imperfection, whether localized or not, nearly always decrease, but can also
\emph{increase} the persistent current, depending on the character of the
imperfection and the on-site interaction. The calculations are generally in
agreement with more specialized studies. In most cases the electron spin plays
an important role.

31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
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The categories of this paper are: adap-org
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The categories of this paper are: dg-ga
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph