Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Stationary scalar clouds around a BTZ black hole   We establish the existence of stationary clouds of massive test scalar fields
around BTZ black holes. These clouds are zero-modes of the superradiant
instability and are possible when Robin boundary conditions (RBCs) are
considered at the AdS boundary. These boundary conditions are the most general
ones that ensure the AdS space is an isolated system, and include, as a
particular case, the commonly considered Dirichlet or Neumann-type boundary
conditions (DBCs or NBCs). We obtain an explicit, closed form, resonance
condition, relating the RBCs that allow the existence of normalizable (and
regular on and outside the horizon) clouds to the system's parameters. Such
RBCs never include pure DBCs or NBCs. We illustrate the spatial distribution of
these clouds, their energy and angular momentum density for some cases. Our
results show that BTZ black holes with scalar hair can be constructed, as the
non-linear realization of these clouds.

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The categories of this paper are: ao-sci
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The categories of this paper are: econ
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The categories of this paper are: cond-mat
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The categories of this paper are: comp-gas
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The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: patt-sol
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The categories of this paper are: eess
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The categories of this paper are: hep-lat
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The categories of this paper are: chem-ph
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The categories of this paper are: nlin
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The categories of this paper are: supr-con
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The categories of this paper are: astro-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph