Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Models of impurities in valence bond spin chains and ladders   We present the class of models of a nonmagnetic impurity in S=1/2 generalized
ladder with an AKLT-type valence bond ground state, and of a S=1/2 impurity in
the S=1 AKLT chain. The ground state in presence of impurity can be found
exactly. Recently studied phenomenon of local enhancement of antiferromagnetic
correlations around the impurity is absent for this family of models.

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The categories of this paper are: eess
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The categories of this paper are: q-bio
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The categories of this paper are: math-ph
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: dg-ga
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: bayes-an
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The categories of this paper are: econ
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The categories of this paper are: q-alg
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The categories of this paper are: nucl-th
3
The categories of this paper are: physics
2
The categories of this paper are: math