Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gravitational Lensing of Rays through the Levitating Atmospheres of
  Compact Objects   Electromagnetic rays travel on curved paths under the influence of gravity.
When a dispersive optical medium is included, these trajectories are
frequency-dependent. In this work we consider the behaviour of rays when a
spherically symmetric, luminous compact object described by the Schwarzschild
metric is surrounded by an optically thin shell of plasma supported by
radiation pressure. Such levitating atmospheres occupy a position of stable
radial equilibrium, where radiative flux and gravitational effects are
balanced. Using general relativity and an inhomogeneous plasma we find the
existence of a stable circular orbit within the atmospheric shell for
low-frequency rays. We explore families of bound orbits that exist between the
shell and the compact object, and identify sets of novel periodic orbits.
Finally, we examine conditions necessary for the trapping and escape of
low-frequency radiation.

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The categories of this paper are: cmp-lg
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The categories of this paper are: supr-con
19
The categories of this paper are: eess
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The categories of this paper are: mtrl-th
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The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs
11
The categories of this paper are: hep-lat
15
The categories of this paper are: nucl-ex
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The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
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The categories of this paper are: bayes-an
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The categories of this paper are: alg-geom
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The categories of this paper are: ao-sci