Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A short answer to critics of our article "Eppur si espande"
  [arXiv:astro-ph/0612155]   Recently [arXiv:astro-ph/0612155] we presented a formal mathematical proof
that, contrary to a widespread misconception, cosmological expansion cannot be
understood as the motion of galaxies in non-expanding space. We showed that the
cosmological redshift must be physically interpreted as the expansion of space.
Although our proof was generally accepted, a few authors disagreed. We rebut
their criticism in this Note.

4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
25
The categories of this paper are: patt-sol
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The categories of this paper are: quant-ph
11
The categories of this paper are: hep-lat
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The categories of this paper are: solv-int
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The categories of this paper are: stat
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The categories of this paper are: eess
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The categories of this paper are: math
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The categories of this paper are: plasm-ph
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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: physics
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The categories of this paper are: chem-ph
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The categories of this paper are: ao-sci