Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Bound Pairs: Direct Evidence for Long-range Attraction between
  Like-Charged Colloids   We report observations of stable bound pairs in very dilute deionized aqueous
suspensions of highly charged polystyrene colloidal particles, with monovalent
counterions, using a confocal laser scanning microscope. Through an analysis of
several thousands of time series of confocal images recorded deep inside the
bulk suspension, we find that the measured pair-potential, U(r) has a
long-range attractive component with well depths larger than the thermal
energy. These observations provide a direct and unequivocal evidence for the
existence of long-range attraction in U(r) of like-charged colloidal particles.

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The categories of this paper are: atom-ph
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
29
The categories of this paper are: funct-an
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The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
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The categories of this paper are: supr-con
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The categories of this paper are: bayes-an
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The categories of this paper are: ao-sci
2
The categories of this paper are: math
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The categories of this paper are: stat
5
The categories of this paper are: gr-qc
3
The categories of this paper are: physics