Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Diverging thermal expansion of the spin-ladder system
  (C$_5$H$_{12}$N)$_2$CuBr$_4$   We present high-resolution measurements of the $c^\star$-axis thermal
expansion and magnetostriction of piperidinium copper bromide \hp. The
experimental data at low temperatures is well accounted for by a two-leg
spin-ladder Hamiltonian. The thermal expansion shows a complex behaviour with
various sign changes and approaches a $1/\sqrt{T}$ divergence at the critical
fields. All low-temperature features are semi-quantitatively explained within a
free fermion model; full quantitative agreement is obtained with Quantum Monte
Carlo simulations.

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The categories of this paper are: hep-lat
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The categories of this paper are: eess
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The categories of this paper are: math
33
The categories of this paper are: plasm-ph
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The categories of this paper are: q-bio
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The categories of this paper are: econ
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The categories of this paper are: nucl-ex
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The categories of this paper are: atom-ph
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The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: patt-sol
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The categories of this paper are: stat
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: bayes-an