Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic Excitations in the Spin Gap System TlCuCl$_3$   Single-crystal neutron inelastic scattering was performed in order to
investigate the magnetic excitations in the spin gap system TlCuCl$_3$. The
constant-${\bf Q}$ energy scan profiles were collected in the $a^*-c^*$ plane.
Three excitations are observed for $E{\leq}15$ meV. One of the excitations is
identified to be magnetic excitation. The lowest magnetic excitation with
$E\sim 0.5$ meV occurs at ${\bf Q}=(1, 0, 1)$, as observed in KCuCl$_3$. The
dispersion relation of the magnetic excitation can be fitted to the dispersion
formula derived from the weakly coupled dimer model. The intradimer interaction
is evaluated as $J=5.23$ meV, which coincides with the value estimated from the
susceptibility data. However, one of the interdimer interactions obtained is so
large that the weakly coupled dimer model is broken down.

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The categories of this paper are: funct-an
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The categories of this paper are: q-bio
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The categories of this paper are: patt-sol
3
The categories of this paper are: physics
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-ex
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The categories of this paper are: nlin
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The categories of this paper are: comp-gas
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The categories of this paper are: bayes-an
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The categories of this paper are: gr-qc
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The categories of this paper are: supr-con
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The categories of this paper are: dg-ga
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The categories of this paper are: math
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The categories of this paper are: nucl-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: econ