Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Apsidal Behavior Among Planetary Orbits: Testing the Planet-Planet
  Scattering Model   Planets in extrasolar systems tend to interact such that their orbits lie
near a boundary between apsidal libration and circulation, a "separatrix", with
one eccentricity periodically reaching near-zero. One explanation, applied to
the Upsilon Andromedae system, assumed three original planets on circular
orbits. One is ejected, leaving the other two with near-separatrix behavior. We
test that model by integrating hundreds of hypothetical, unstable planetary
systems that eject a planet. We find that the probability that the remaining
planets exhibit near-separatrix motion is small (< 5% compared with nearly 50%
of observed systems). Moreover, while observed librating systems are evenly
divided between aligned and anti-aligned pericenter longitudes, the scattering
model strongly favors alignment. Alternative scattering theories are proposed,
which may provide a more satisfactory fit with observed systems.

14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
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The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
36
The categories of this paper are: cmp-lg
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The categories of this paper are: eess
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The categories of this paper are: supr-con
1
The categories of this paper are: cs
3
The categories of this paper are: physics
18
The categories of this paper are: econ
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The categories of this paper are: solv-int
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The categories of this paper are: quant-ph
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The categories of this paper are: q-bio
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The categories of this paper are: q-alg