Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Extended bodies with quadrupole moment interacting with gravitational
  monopoles: reciprocity relations   An exact solution of Einstein's equations representing the static
gravitational field of a quasi-spherical source endowed with both mass and mass
quadrupole moment is considered. It belongs to the Weyl class of solutions and
reduces to the Schwarzschild solution when the quadrupole moment vanishes. The
geometric properties of timelike circular orbits (including geodesics) in this
spacetime are investigated. Moreover, a comparison between geodesic motion in
the spacetime of a quasi-spherical source and non-geodesic motion of an
extended body also endowed with both mass and mass quadrupole moment as
described by Dixon's model in the gravitational field of a Schwarzschild black
hole is discussed. Certain "reciprocity relations" between the source and the
particle parameters are obtained, providing a further argument in favor of the
acceptability of Dixon's model for extended bodies in general relativity.

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The categories of this paper are: hep-th
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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: solv-int
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The categories of this paper are: hep-lat
16
The categories of this paper are: stat
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The categories of this paper are: nucl-th
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The categories of this paper are: astro-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: nlin
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The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-ph
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys