Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Absence of effective spins 1/2 induced by nonmagnetic impurities in a
  class of low-dimensional magnets   We show that doping a Majumdar--Ghosh chain with non-magnetic impurities does
{\it not} produce almost free spins 1/2. The difference between this system and
other spin liquids, such as unfrustrated spin ladders, is illustrated in the
context of the general dimerized, frustrated spin chain. By detailed analysis
of the excitation spectra of finite chains with two impurities, we investigate
the evolution of the screening affecting impurity-induced free spins, and of
the sign and magnitude of their effective interactions. We comment on a
possible connection to impurity-doping experiments in CuGeO_3.

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The categories of this paper are: funct-an
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The categories of this paper are: adap-org
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The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
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The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
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The categories of this paper are: plasm-ph
2
The categories of this paper are: math
35
The categories of this paper are: mtrl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: solv-int
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The categories of this paper are: chem-ph
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The categories of this paper are: supr-con