Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Resistive and sympathetic cooling of highly-charged-ion clouds in a
  Penning trap   We present measurements of resistive and sympathetic cooling of ion clouds
confined in a Penning trap. For resistive cooling of a cloud consisting of one
ion species, we observe a significant deviation from exponential cooling
behavior which is explained by an energy-transfer model. The observed
sympathetic cooling of simultaneously confined ion species shows a quadratic
dependence on the ion charge state and is hence in agreement with expectations
from the physics of dilute non-neutral plasmas.

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The categories of this paper are: patt-sol
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The categories of this paper are: bayes-an
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The categories of this paper are: ao-sci
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The categories of this paper are: dg-ga
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The categories of this paper are: alg-geom
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The categories of this paper are: stat
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-lat
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The categories of this paper are: cond-mat
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The categories of this paper are: math
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The categories of this paper are: q-alg
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The categories of this paper are: math-ph
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The categories of this paper are: funct-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: supr-con