Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The cosine law of field enhancement factor variation: generic emitter
  shapes   The cosine law of field enhancement factor variation was recently derived for
a hemi-ellipsoidal emitter and numerically established for other smooth emitter
shapes (Biswas et al, Ultramicroscopy, 185, 1 (2018)). An analytical derivation
is provided here for general smooth vertical emitter shapes aligned in the
direction of the asymptotic electrostatic field. The law is found to hold in
the neighbourhood of the emitter apex from where field emisson pre-dominantly
occurs.

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The categories of this paper are: ao-sci
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The categories of this paper are: math
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The categories of this paper are: econ
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The categories of this paper are: q-alg
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The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: eess
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The categories of this paper are: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: q-bio
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The categories of this paper are: nlin
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The categories of this paper are: astro-ph
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The categories of this paper are: adap-org
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The categories of this paper are: solv-int
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The categories of this paper are: comp-gas