Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Strange behavior of persistent currents in small Hubbard rings   We show exactly that small Hubbard rings exhibit unusual kink-like structures
giving anomalous oscillations in persistent current. Singular behavior of
persistent current disappears in some cases. In half-filled systems mobility
gradually drops to zero with interaction, while it converges to some finite
value in non-half-filled cases.

20
The categories of this paper are: acc-phys
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The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
37
The categories of this paper are: supr-con
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom
6
The categories of this paper are: astro-ph
11
The categories of this paper are: hep-lat
16
The categories of this paper are: stat
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
3
The categories of this paper are: physics