Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Very low-frequency excitations in frustrated two-dimensional $S=1/2$
  Heisenberg antiferromagnets   muSR and 7Li NMR relaxation measurements in frustrated two-dimensional S=1/2
Heisenberg antiferromagnets on a square lattice are presented. It is found that
both in Li2VOSiO4 and Li2VOGeO4, spin dynamics at frequencies well below the
Heisenberg exchange frequency are present. These dynamics are associated with
the motions of walls separating coexisting collinear domains with a magnetic
wave vector rotated by 90 degrees.

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The categories of this paper are: econ
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The categories of this paper are: hep-ex
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The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-lat
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The categories of this paper are: stat
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The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
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The categories of this paper are: q-bio
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The categories of this paper are: hep-th
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The categories of this paper are: atom-ph