Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Universal Behavior of the Spin-Echo Decay Rate in La_2CuO_4   We present a theoretical expression for the spin-echo decay rate, 1/T_2G, in
the quantum-critical regime of square lattice quantum antiferromagnets. Our
results are in good agreement with recent experimental data by Imai et al.
[Phys. Rev. Lett. v.71, 1254 (1993)] for La_2CuO_4.

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The categories of this paper are: ao-sci
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The categories of this paper are: physics
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The categories of this paper are: hep-lat
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The categories of this paper are: plasm-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-th
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: math
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
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The categories of this paper are: adap-org
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The categories of this paper are: stat