Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Reissner-Nordstr\"om black holes in extended Palatini theories   We study static, spherically symmetric solutions with an electric field in an
extension of general relativity (GR) containing a Ricci-squared term and
formulated in the Palatini formalism. We find that all the solutions present a
central core whose area is proportional to the Planck area times the number of
charges. Far from the core, curvature invariants quickly tend to those of the
usual Reissner-Nordstr\"om solution, though the structure of horizons may be
different. In fact, besides the structures found in the Reissner-Nordstr\"om
solution of GR, we find black hole solutions with just one nondegenerate
horizon (Schwarzschild-like), and nonsingular black holes and naked cores. The
charge-to-mass ratio of the nonsingular solutions implies that the core matter
density is independent of the specific amounts of charge and mass and of order
the Planck density. We discuss the physical implications of these results for
astrophysical and microscopic black holes, construct the Penrose diagrams of
some illustrative cases, and show that the maximal analytical extension of the
nonsingular solutions implies a bounce of the radial coordinate.

19
The categories of this paper are: eess
16
The categories of this paper are: stat
10
The categories of this paper are: q-bio
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
2
The categories of this paper are: math
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
22
The categories of this paper are: chao-dyn
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat