Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nemesis Reconsidered   The hypothesis of a companion object (Nemesis) orbiting the Sun was motivated
by the claim of a terrestrial extinction periodicity, thought to be mediated by
comet showers. The orbit of a distant companion to the Sun is expected to be
perturbed by the Galactic tidal field and encounters with passing stars, which
will induce variation in the period. We examine the evidence for the previously
proposed periodicity, using two modern, greatly improved paleontological
datasets of fossil biodiversity. We find that there is a narrow peak at 27 My
in the cross-spectrum of extinction intensity time series between these
independent datasets. This periodicity extends over a time period nearly twice
that for which it was originally noted. An excess of extinction events are
associated with this periodicity at 99% confidence. In this sense we confirm
the originally noted feature in the time series for extinction. However, we
find that it displays extremely regular timing for about 0.5 Gy. The regularity
of the timing compared with earlier calculations of orbital perturbation would
seem to exclude the Nemesis hypothesis as a causal factor.

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The categories of this paper are: hep-ph
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
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The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
28
The categories of this paper are: alg-geom
4
The categories of this paper are: cond-mat
23
The categories of this paper are: solv-int
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The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
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The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
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The categories of this paper are: hep-lat
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The categories of this paper are: econ