Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spin waves in a two dimensional p-wave superconductor: Sr$_2$RuO$_4$   We study spin excitations in a two dimensional p-wave superconductor with
${\vec \Delta} = {\hat d}({\hat k}_1 \pm i {\hat k}_2)$ symmetry in the context
of the newly discovered superconducting Sr$_2$RuO$_4$. The polarization and
spectrum of spin wave excitations are identified and their experimental
consequences are discussed.

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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: q-bio
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The categories of this paper are: bayes-an
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The categories of this paper are: astro-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-fin
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: comp-gas
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The categories of this paper are: solv-int
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The categories of this paper are: hep-ph
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The categories of this paper are: adap-org
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The categories of this paper are: stat
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The categories of this paper are: acc-phys