Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nonlinear sigma model study of a frustrated spin ladder   A model of two-leg spin-S ladder with two additional frustrating diagonal
exchange couplings J_{D}, J_{D}' is studied within the framework of the
nonlinear sigma model approach. The phase diagram has a rich structure and
contains 2S gapless phase boundaries which split off the boundary to the fully
saturated ferromagnetic phase when J_{D} and J_{D}' become different. For the
S=1/2 case, the phase boundaries are identified as separating two topologically
distinct Haldane-type phases discussed recently by Kim et al.
(cond-mat/9910023).

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The categories of this paper are: q-bio
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The categories of this paper are: atom-ph
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The categories of this paper are: eess
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The categories of this paper are: alg-geom
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The categories of this paper are: q-fin
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The categories of this paper are: chem-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: econ
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The categories of this paper are: math
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The categories of this paper are: stat
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The categories of this paper are: nlin
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-alg
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The categories of this paper are: funct-an
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The categories of this paper are: gr-qc
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The categories of this paper are: dg-ga