Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Radiative Tail in $\pi_{e2}$ Decay and Some Comments on $\mu-e$
  Universality   The result of lowest-order perturbation theory calculations of the photon and
positron spectra in radiative pion(e2) decay are generalized to all orders of
perturbation theory using the structure-function method. An additional source
of radiative corrections to the ratio of the positron and muon channels of pion
decay, due to emission of virtual and real photons and pairs, is considered. It
depends on details of the detection of the final particles and is large enough
to be taken into account in theoretical estimates with a level of accuracy of
0.1%.

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The categories of this paper are: alg-geom
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The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
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The categories of this paper are: q-fin
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The categories of this paper are: solv-int
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The categories of this paper are: comp-gas
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
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The categories of this paper are: dg-ga
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
3
The categories of this paper are: physics
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The categories of this paper are: funct-an
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The categories of this paper are: q-alg