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Author |
Afonso, V.I.; Olmo, G.J.; Orazi, E.; Rubiera-Garcia, D. |
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Title |
New scalar compact objects in Ricci-based gravity theories |
Type |
Journal Article |
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Year |
2019 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
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Volume |
12 |
Issue |
12 |
Pages |
044 - 20pp |
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Keywords |
modified gravity; gravity; GR black holes; Wormholes |
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Abstract |
Taking advantage of a previously developed method, which allows to map solutions of General Relativity into a broad family of theories of gravity based on the Ricci tensor (Ricci-based gravities), we find new exact analytical scalar field solutions by mapping the free-field static, spherically symmetric solution of General Relativity (GR) into quadratic f(R) gravity and the Eddington-inspired Born-Infeld gravity. The obtained solutions have some distinctive feature below the would-be Schwarzschild radius of a configuration with the same mass, though in this case no horizon is present. The compact objects found include wormholes, compact balls, shells of energy with no interior, and a new kind of object which acts as a kind of wormhole membrane. The latter object has Euclidean topology but connects antipodal points of its surface by transferring particles and null rays across its interior in virtually zero affine time. We point out the relevance of these results regarding the existence of compact scalar field objects beyond General Relativity that may effectively act as black hole mimickers. |
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Address |
[Afonso, Victor I.] Univ Fed Campina Grande, Unidade Acad Fis, BR-58429900 Campina Grande, PB, Brazil, Email: viafonso@df.ufcg.edu.br; |
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Iop Publishing Ltd |
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English |
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1475-7516 |
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Notes |
WOS:000507261900041 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4252 |
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Author |
Guerrero, M.; Mora-Perez, G.; Olmo, G.J.; Orazi, E.; Rubiera-Garcia, D. |
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Title |
Rotating black holes in Eddington-inspired Born-Infeld gravity: an exact solution |
Type |
Journal Article |
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Year |
2020 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
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Volume |
07 |
Issue |
7 |
Pages |
058 - 31pp |
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Keywords |
modified gravity; GR black holes; Wormholes |
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Abstract |
We find an exact, rotating charged black hole solution within Eddington-inspired Born-Infeld gravity. To this end we employ a recently developed correspondence or mapping between modified gravity models built as scalars out of contractions of the metric with the Ricci tensor, and formulated in metric-affine spaces (Ricci-Based Gravity theories) and General Relativity. This way, starting from the Kerr-Newman solution, we show that this mapping bring us the axisymmetric solutions of Eddington-inspired Born-Infeld gravity coupled to a certain model of non-linear electrodynamics. We discuss the most relevant physical features of the solutions obtained this way, both in the spherically symmetric limit and in the fully rotating regime. Moreover, we further elaborate on the potential impact of this important technical progress for bringing closer the predictions of modified gravity with the astrophysical observations of compact objects and gravitational wave astronomy. |
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Address |
[Guerrero, Merce; Rubiera-Garcia, Diego] Univ Complutense Madrid, Dept Fis Teor, E-28040 Madrid, Spain, Email: merguerr@ucm.es; |
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Iop Publishing Ltd |
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English |
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1475-7516 |
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Notes |
WOS:000609085900005 |
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no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4682 |
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Author |
Guerrero, M.; Olmo, G.J.; Rubiera-Garcia, D. |
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Title |
Double shadows of reflection-asymmetric wormholes supported by positive energy thin-shells |
Type |
Journal Article |
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Year |
2021 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
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Volume |
04 |
Issue |
4 |
Pages |
066 - 26pp |
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Keywords |
modified gravity; Wormholes; gravity |
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Abstract |
We consider reflection-asymmetric thin-shell wormholes within Palatini f(R) gravity using a matching procedure of two patches of electrovacuum space-times at a hypersurface (the shell) via suitable junction conditions. The conditions for having (linearly) stable wormholes supported by positive-energy matter sources are determined. We also identify some subsets of parameters able to locate the shell radius above the event horizon (when present) but below the photon sphere (on both sides). We illustrate with an specific example that such two photon spheres allow an observer on one of the sides of the wormhole to see another (circular) shadow in addition to the one generated by its own photon sphere, which is due to the photons passing above the maximum of the effective potential on its side and bouncing back across the throat due to a higher effective potential on the other side. We finally comment on the capability of these double shadows to seek for traces of new gravitational physics beyond that described by General Relativity. |
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Address |
[Guerrero, Merce; Rubiera-Garcia, Diego] Univ Complutense Madrid, Dept Fis Teor, E-28040 Madrid, Spain, Email: merguerr@ucm.es; |
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Publisher |
Iop Publishing Ltd |
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English |
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1475-7516 |
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Conference |
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Notes |
WOS:000644501000029 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4823 |
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Author |
Guerrero, M.; Olmo, G.J.; Rubiera-Garcia, D.; Saez-Chillon Gomez, D. |
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Title |
Shadows and optical appearance of black bounces illuminated by a thin accretion disk |
Type |
Journal Article |
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Year |
2021 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
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Volume |
08 |
Issue |
8 |
Pages |
036 - 19pp |
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Keywords |
GR black holes; Wormholes; modified gravity; accretion |
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Abstract |
We study the light rings and shadows of an uniparametric family of spherically symmetric geometries interpolating between the Schwarzschild solution, a regular black hole, and a traversable wormhole, and dubbed as black bounces, all of them sharing the same critical impact parameter. We consider the ray-tracing method in order to study the impact parameter regions corresponding to the direct, lensed, and photon ring emissions, finding a broadening of all these regions for black bounce solutions as compared to the Schwarzschild one. Using this, we determine the optical appearance of black bounces when illuminated by three standard toy models of optically and geometrically thin accretion disks viewed in face-on orientation. |
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Address |
[Guerrero, Merce; Rubiera-Garcia, Diego] Univ Complutense Madrid, Dept Fis Teor, E-28040 Madrid, Spain, Email: merguerr@ucm.es; |
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Publisher |
Iop Publishing Ltd |
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English |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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ISSN |
1475-7516 |
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Conference |
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Notes |
WOS:000686656000022 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
4943 |
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Author |
Guerrero, M.; Mora-Perez, G.; Olmo, G.J.; Orazi, E.; Rubiera-Garcia, D. |
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Title |
Charged BTZ-type solutions in Eddington-inspired Born-Infeld gravity |
Type |
Journal Article |
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Year |
2021 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
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Volume |
11 |
Issue |
11 |
Pages |
025 - 23pp |
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Keywords |
modified gravity; Exact solutions; black holes and black hole thermodynamics in GR and beyond; Wormholes |
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Abstract |
We construct an axially symmetric solution of Eddington-inspired Born-Infeld gravity coupled to an electromagnetic field in 2 + 1 dimensions including a (negative) cosmological constant term. This is achieved by using a recently developed mapping procedure that allows to generate solutions in certain families of metric-affine gravity theories starting from a known seed solution of General Relativity, which in the present case corresponds to the electrically charged Banados-Teitelboim-Zanelli (BTZ) solution. We discuss the main features of the new configurations, including the modifications to the ergospheres and horizons, the emergence of wormhole structures, and the consequences for the regularity (or not) of these space-times via geodesic completeness. |
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Address |
[Guerrero, Merce; Rubiera-Garcia, Diego] Univ Complutense Madrid, Dept Fis Teor, Plaza Ciencias S-N, E-28040 Madrid, Spain, Email: merguerr@ucm.es; |
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IOP Publishing Ltd |
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English |
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Series Volume |
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Series Issue |
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ISSN |
1475-7516 |
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Expedition |
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Conference |
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Notes |
WOS:000727716400006 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
5050 |
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Author |
Afonso, V.I.; Mora-Perez, G.; Olmo, G.J.; Orazi, E.; Rubiera-Garcia, D. |
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Title |
An infinite class of exact rotating black hole metrics of modified gravity |
Type |
Journal Article |
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Year |
2022 |
Publication |
Journal of Cosmology and Astroparticle Physics |
Abbreviated Journal |
J. Cosmol. Astropart. Phys. |
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Volume |
03 |
Issue |
3 |
Pages |
052 - 14pp |
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Keywords |
Exact solutions; black holes and black hole thermodynamics in GR and beyond; Gauss-Bonnet-Lovelock-Horndeski-Palatini etc gravity theories; modified gravity |
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Abstract |
We build an infinite class of exact axisymmetric solutions of a metric-affine gravity theory, namely, Eddington-inspired Born-Infeld gravity, coupled to an anisotropic fluid as a matter source. The solution-generating method employed is not unique of this theory but can be extended to other Ricci-Based Gravity theories (RBGs), a class of theories built out of contractions of the Ricci tensor with the metric. This method exploits a correspondence between the space of solutions of General Relativity and that of RBGs, and is independent of the symmetries of the problem. For the particular case in which the fluid is identified with non-linear electromagnetic fields we explicitly derive the corresponding axisymmetric solutions. Finally, we use this result to work out the counterpart of the Kerr-Newman black hole when Maxwell electrodynamics is set on the metric-affine side. Our results open up an exciting new avenue for testing new gravitational phenomenology in the fields of gravitational waves and shadows out of rotating black holes. |
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Address |
[Afonso, Victor, I] Univ Fed Campina Grande, Unidade Academ Fis, BR-58429900 Campina Grande, Paraiba, Brazil, Email: viafonso@df.ufcg.edu.br; |
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Publisher |
IOP Publishing Ltd |
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English |
Summary Language |
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Series Editor |
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ISSN |
1475-7516 |
ISBN |
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Area |
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Conference |
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Notes |
WOS:000776994500002 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
5185 |
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Author |
Olmo, G.J.; Rubiera-Garcia, D. |
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Title |
Palatini f(R) black holes in nonlinear electrodynamics |
Type |
Journal Article |
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Year |
2011 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
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Volume |
84 |
Issue |
12 |
Pages |
124059 - 14pp |
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Keywords |
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Abstract |
The electrically charged Born-Infeld black holes in the Palatini formalism for f(R) theories are analyzed. Specifically we study those supported by a theory f(R) = R +/- R(2)/R(P), where R(P) is Planck's curvature. These black holes only differ from their General Relativity counterparts very close to the center but may give rise to different geometrical structures in terms of inner horizons. The nature and strength of the central singularities are also significantly affected. In particular, for the model f(R) = R – R(2)/R(P) the singularity is shifted to a finite radius, r(+), and the Kretschmann scalar diverges only as 1/(r-r(+))(2). |
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Address |
[Olmo, Gonzalo J.] Univ Valencia, Ctr Mixto Univ Valencia CSIC, Dept Fis Teor, E-46100 Valencia, Spain, Email: gonzalo.olmo@csic.es |
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Publisher |
Amer Physical Soc |
Place of Publication |
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English |
Summary Language |
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ISSN |
1550-7998 |
ISBN |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000298666600005 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ pastor @ |
Serial |
878 |
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Author |
Olmo, G.J.; Rubiera-Garcia, D. |
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Title |
Reissner-Nordstrom black holes in extended Palatini theories |
Type |
Journal Article |
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Year |
2012 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
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Volume |
86 |
Issue |
4 |
Pages |
044014 - 15pp |
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Keywords |
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Abstract |
We study static, spherically symmetric solutions with an electric field in an extension of general relativity 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-Nordstrom solution, though the structure of horizons may be different. In fact, besides the structures found in the Reissner-Nordstrom solution of general relativity, 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. |
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Address |
[Olmo, Gonzalo J.] Univ Valencia, Ctr Mixto, CSIC, Dept Fis Teor, E-46100 Valencia, Spain |
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Publisher |
Amer Physical Soc |
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English |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1550-7998 |
ISBN |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000307276200003 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ pastor @ |
Serial |
1114 |
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Author |
Martinez-Asencio, J.; Olmo, G.J.; Rubiera-Garcia, D. |
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Title |
Black hole formation from a null fluid in extended Palatini gravity |
Type |
Journal Article |
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Year |
2012 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
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Volume |
86 |
Issue |
10 |
Pages |
104010 - 8pp |
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Keywords |
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Abstract |
We study the formation and perturbation of black holes by null fluxes of neutral matter in a quadratic extension of general relativity formulated a la Palatini. Working in a spherically symmetric space-time, we obtain an exact analytical solution for the metric that extends the usual Vaidya-type solution to this type of theory. We find that the resulting space-time is formally that of a Reissner-Nordstrom black hole but with an effective charge term carrying the wrong sign in front of it. This effective charge is directly related to the luminosity function of the radiation stream. When the ingoing flux vanishes, the charge term disappears and the space-time relaxes to that of a Schwarzschild black hole. We provide two examples that illustrate the formation of a black hole from Minkowski space and the perturbation by a finite pulse of radiation of an existing Schwarzschild black hole. |
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Address |
[Martinez-Asencio, Jesus; Olmo, Gonzalo J.] Univ Valencia, Dept Fis Teor, E-46100 Valencia, Spain, Email: gonzalo.olmo@csic.es; |
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Amer Physical Soc |
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English |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1550-7998 |
ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000310686900007 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
no |
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Call Number |
IFIC @ pastor @ |
Serial |
1202 |
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Author |
Olmo, G.J.; Rubiera-Garcia, D. |
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Title |
Importance of torsion and invariant volumes in Palatini theories of gravity |
Type |
Journal Article |
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Year |
2013 |
Publication |
Physical Review D |
Abbreviated Journal |
Phys. Rev. D |
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Volume |
88 |
Issue |
8 |
Pages |
084030 - 11pp |
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Keywords |
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Abstract |
We study the field equations of extensions of general relativity formulated within a metric-affine formalism setting torsion to zero (Palatini approach). We find that different (second-order) dynamical equations arise depending on whether torsion is set to zero (i) a priori or (ii) a posteriori, i.e., before or after considering variations of the action. Considering a generic family of Ricci-squared theories, we show that in both cases the connection can be decomposed as the sum of a Levi-Civita connection and terms depending on a vector field. However, while in case (i) this vector field is related to the symmetric part of the connection, in (ii) it comes from the torsion part and, therefore, it vanishes once torsion is completely removed. Moreover, the vanishing of this torsion-related vector field immediately implies the vanishing of the antisymmetric part of the Ricci tensor, which therefore plays no role in the dynamics. Related to this, we find that the Levi-Civita part of the connection is due to the existence of an invariant volume associated with an auxiliary metric h(mu v), which is algebraically related with the physical metric g(mu v). |
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Address |
[Olmo, Gonzalo J.] Ctr Mixto Univ Valencia CSIC, Dept Fis Teor, Valencia 46100, Spain, Email: gonzalo.olmo@csic.es; |
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Publisher |
Amer Physical Soc |
Place of Publication |
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English |
Summary Language |
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Original Title |
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Series Title |
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Abbreviated Series Title |
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Series Volume |
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Series Issue |
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Edition |
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ISSN |
1550-7998 |
ISBN |
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Medium |
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Area |
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Expedition |
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Conference |
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Notes |
WOS:000326107300007 |
Approved |
no |
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Is ISI |
yes |
International Collaboration |
yes |
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Call Number |
IFIC @ pastor @ |
Serial |
1630 |
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