Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Order m alpha^8 Contributions to the Decay Rate of Orthopositronium   We discuss how contributions to the order ${\cal O} (m \alpha^8)$
orthopositronium decay rate can be separated into two categories, one due to
relativistic momenta and calculable in terms of QED scattering amplitudes, the
other due to low momenta and calculable in the simpler framework of a
low-energy effective theory (NRQED). We report new results for all low-momentum
contributions, and give a formula relating the remaining contributions to
conventional (on-shell) QED scattering amplitudes.

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The categories of this paper are: nlin
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The categories of this paper are: q-fin
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The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
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The categories of this paper are: cs
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The categories of this paper are: plasm-ph
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The categories of this paper are: eess
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The categories of this paper are: quant-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: q-bio