Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stable Bound Orbits of Massless Particles around a Black Ring   We study the geodesic motion of massless particles in singly rotating black
ring spacetimes. We find stable stationary orbits of massless particles in
toroidal spiral shape in the case that the thickness parameter of a black ring
is less than a critical value. Furthermore, there exist nonstationary massless
particles bounded in a finite region outside the horizon. This is the first
example of stable bound orbits of massless particles around a black object.

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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: adap-org
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The categories of this paper are: astro-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-lat
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The categories of this paper are: q-bio
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The categories of this paper are: quant-ph
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The categories of this paper are: q-fin
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The categories of this paper are: supr-con
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The categories of this paper are: atom-ph
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The categories of this paper are: dg-ga