Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Comment on "Frequency shifts in NIST Cs primary frequency standards due
  to transverse rf field gradients"   We discuss the theoretical treatment of the microwave lensing frequency shift
of the NIST-F1 and F2 atomic fountain clocks by Ashby et al. [Phy. Rev. A. 91,
033624 (2015)]. The shifts calculated by NIST are much smaller than the
previously evaluated microwave lensing frequency shifts of other clocks
contributing to International Atomic Time. We identify several fundamental
problems in the NIST treatment and demonstrate that each significantly affects
their results. We also show a smooth transition of microwave lensing frequency
shifts to the photon recoil shift for large wave packets.

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The categories of this paper are: math-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: nlin
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
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The categories of this paper are: eess
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
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The categories of this paper are: q-bio
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The categories of this paper are: hep-lat
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The categories of this paper are: supr-con
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The categories of this paper are: chem-ph
1
The categories of this paper are: cs
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The categories of this paper are: funct-an
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The categories of this paper are: acc-phys
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The categories of this paper are: q-fin