Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Geodesic motion around a distorted static black hole   In this paper we study geodesic motion around a distorted Schwarzschild black
hole. We consider both timelike and null geodesics which are confined to the
black hole's equatorial plane. Such geodesics generically exist if the
distortion field has only even interior multipole moments and so the field is
symmetric with respect to the equatorial plane. We specialize to the case of
distortions defined by a quadrupole Weyl moment. An analysis of the effective
potential for equatorial timelike geodesics shows that finite stable orbits
outside the black hole are possible only for $q\in(q_{\text{min}},
q_{\text{max}}]$, where $q_{\text{min}}\approx-0.0210$ and
$q_{\text{max}}\approx2.7086\times10^{-4}$, while for null equatorial geodesics
a finite stable orbit outside the black hole is possible only for
$q\in[q_{\text{min}},0)$. Moreover, the innermost stable circular orbits
(ISCOs) are closer to the distorted black hole horizon than those of an
undistorted Schwarzschild black hole for $q\in(q_{\text{min}},0)$ and a null
ISCO exists for $q=q_{\text{min}}$. These results shows that an external
distortion of a negative and sufficiently small quadrupole moment tends to
stabilize motion of massive particles and light.

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The categories of this paper are: math-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: plasm-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-lat
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The categories of this paper are: solv-int
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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: supr-con
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The categories of this paper are: alg-geom
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The categories of this paper are: q-bio
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-th