Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Shadow and Deflection Angle of Rotating Black Holes in Perfect Fluid
  Dark Matter with a Cosmological Constant   The presence of dark matter around a black hole remarkably affects its
spacetime. We consider the effects of dark matter on the shadow of a new
solution to the Einstein equations that describes a rotating black hole in the
background of perfect dark matter fluid (PFDM), along with its extension to
nonzero cosmological constant $\Lambda$. Working in Boyer-Lindquist
coordinates, we consider the effects of the PFDM parameter $\alpha$ on the
shadow cast by a black hole with respect to an observer at position
$(r_o,\theta_o)$. By applying the Gauss-Bonnet theorem to the optical geometry
we find that notable distortions from a Kerr black hole can occur. We describe
their dependence on $\alpha$ and $\Lambda$.

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The categories of this paper are: physics
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The categories of this paper are: eess
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: q-fin
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The categories of this paper are: funct-an
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: nlin
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The categories of this paper are: quant-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: mtrl-th
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The categories of this paper are: solv-int