Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Update on $|V_{us}|$ and $|V_{us}/V_{ud}|$ from semileptonic kaon and
  pion decays   We discuss the recent progress in the study of semileptonic kaon and pion
decays, including new experimental results, improved electroweak radiative
corrections, form factor calculations and isospin-breaking effects. As a
result, we obtain $|V_{us}|=0.22309(40)(39)(3)$ from kaon semileptonic decays
and $|V_{us}/V_{ud}|=0.22908(66)(41)(40)(2)(1)$ from the ratio between the kaon
and pion semileptonic decay rates. We report an apparent violation of the
top-row Cabibbo-Kobayashi-Maskawa matrix unitarity at a $3.2\sim 5.6\sigma$
level, and a discrepancy at a $2.2\sigma$ level between the value of
$|V_{us}/V_{ud}|$ determined from the vector and axial charged weak
interactions. Prospects for future improvements in those comparative precision
tests involving $|V_{ud}|$, $|V_{us}|$ and their implications for physics
beyond the Standard Model are described.

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The categories of this paper are: econ
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The categories of this paper are: dg-ga
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The categories of this paper are: stat
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The categories of this paper are: math-ph
3
The categories of this paper are: physics
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The categories of this paper are: comp-gas
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
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The categories of this paper are: gr-qc
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The categories of this paper are: eess
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The categories of this paper are: bayes-an
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The categories of this paper are: solv-int
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The categories of this paper are: astro-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: math