Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The E\"{o}tv\"{o}s Paradox: The Enduring Significance of E\"{o}tv\"{o}s'
  Most Famous Paper   Following the death of Baron Lor\'{a}nd von E\"{o}tv\"{o}s in 1919, his
collaborators Desiderius Pek\'{a}r and Eugen Fekete co-authored a paper in 1922
containing the results of a series of earlier experiments testing the identity
of inertial and gravitational mass, the Weak Equivalence Principle (WEP).
Although the so-called "EPF" paper made no claim for any WEP violations, a
subsequent 1986 reanalysis of the EPF paper revealed a pattern in their data
suggesting the presence of a new ("fifth") force in nature. Although the EPF
data, and the 1986 reanalysis of these data, present fairly compelling evidence
for such a fifth force, many contemporary experiments have failed to detect its
presence. Here we summarize the key elements of this "E\"{o}tv\"{o}s paradox,"
and suggest some possible paths to a resolution. Along the way we also discuss
the close relationship between E\"{o}tv\"{o}s and Einstein, and consider how
their respective contributions may have been influenced by the other's.

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The categories of this paper are: comp-gas
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The categories of this paper are: funct-an
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The categories of this paper are: chem-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ex
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The categories of this paper are: supr-con
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The categories of this paper are: econ
9
The categories of this paper are: nlin
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-th
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The categories of this paper are: alg-geom
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The categories of this paper are: cs
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The categories of this paper are: mtrl-th
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The categories of this paper are: adap-org
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The categories of this paper are: stat