Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spherical electro-vacuum black holes with resonant, scalar $Q$-hair   The asymptotically flat, spherical, electro-vacuum black holes (BHs) are
shown to support static, spherical configurations of a gauged,
self-interacting, scalar field, minimally coupled to the geometry. Considering
a $Q$-ball type potential for the scalar field, we dub these configurations
$Q$-clouds, in the test field approximation. The clouds exist under a resonance
condition, at the threshold of (charged) superradiance. This is similar to the
stationary clouds supported by Kerr BHs, which exist for a synchronisation
condition, at the threshold of (rotational) superradiance. In contrast with the
rotating case, however, $Q$-clouds require the scalar field to be massive and
self-interacting; no similar clouds exist for massive but free scalar fields.
First, considering a decoupling limit, we construct $Q$-clouds around
Schwarzschild and Reissner-Nordstr\"om BHs, showing there is always a mass gap.
Then, we make the $Q$-clouds backreact, and construct fully non-linear
solutions of the Einstein-Maxwell-gauged scalar system describing spherical,
charged BHs with resonant, scalar $Q$-hair. Amongst other properties, we
observe there is non-uniqueness of charged BHs in this model and the $Q$-hairy
BHs can be entropically preferred over Reissner-Nordstr\"om, for the same
charge to mass ratio; some $Q$-hairy BH solutions can be overcharged. We also
discuss how some well known no-hair theorems in the literature, applying to
electro-vacuum plus minimally coupled scalar fields, are circumvented by this
new type of BHs.

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The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
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The categories of this paper are: supr-con
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The categories of this paper are: chao-dyn
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The categories of this paper are: adap-org
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The categories of this paper are: nucl-th
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The categories of this paper are: q-alg
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The categories of this paper are: mtrl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: math
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The categories of this paper are: cmp-lg
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The categories of this paper are: comp-gas
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The categories of this paper are: q-bio
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-lat
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The categories of this paper are: chem-ph