Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Perspective: From the dipole of a crystallite to the polarization of a
  crystal   The quantum-mechanical expression for the polarization of a crystalline solid
does not bear any resemblance to the (trivial) expression for the dipole of a
bounded crystallite; and in fact it has been proved via a conceptually
different path. Here I show how to alternatively define the dipole of a bounded
sample in a somewhat unconventional way; from such formula, the crystalline
polarization formula -- as routinely implemented in electronic-structure codes
-- follows almost seamlessly.

23
The categories of this paper are: solv-int
10
The categories of this paper are: q-bio
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The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
25
The categories of this paper are: patt-sol
8
The categories of this paper are: hep-ex
35
The categories of this paper are: mtrl-th
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The categories of this paper are: stat
2
The categories of this paper are: math
37
The categories of this paper are: supr-con
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The categories of this paper are: chem-ph
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
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The categories of this paper are: comp-gas
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The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga