Probing Quadratic Gravity with the Event Horizon Telescope

Daas, Jesse; Kuijpers, Kolja; Saueressig, Frank; Wondrak, Michael F.; Falcke, H.

doi:10.48550/arxiv.2204.08480

Cited by 8 publications

(10 citation statements)

References 61 publications

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“…The aforementioned findings achieved by including the traceless part of the nonmetricity tensor into the geometrical framework open the door not only to further phenomenological analyses on this sector of the theory (see [56][57][58][59][60][61][62][63][64][65] for a recent list of observational constraints on extended theories of gravity), but also to new studies concerning the stability of the tensor modes displayed by the action (103). Indeed, whereas the stability of the scalar and vector modes of the torsion and nonmetricity tensors has been analysed in detail for quadratic MAG models [66][67][68][69][70], a thorough study concerning the behaviour of the tensor parts is yet to be performed.…”

Section: Discussionmentioning

confidence: 99%

New black hole solutions with a dynamical traceless nonmetricity tensor in Metric-Affine Gravity

Bahamonde,

Chevrier,

Valcarcel

2022

Preprint

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In the framework of Metric-Affine Gravity, the existing correspondence between the Einstein tensor and the energy-momentum tensor of matter provided by General Relativity is extended towards a post-Riemannian description in terms of the torsion and nonmetricity fields, which are sourced by the spin, dilation and shear currents of matter. In this work, we focus on the dynamical role of the traceless part of the nonmetricity tensor and their intrinsic connection with shears, defining a model which encloses a new black hole solution endowed with shear charges. We show that the extension in the presence of dynamical torsion and Weyl vector leads to the broadest family of static and spherically symmetric black hole solutions with spin, dilation and shear charges in Metric-Affine Gravity so far.

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Section: Discussionmentioning

confidence: 99%

New black hole solutions with a dynamical traceless nonmetricity tensor in Metric-Affine Gravity

Bahamonde,

Chevrier,

Valcarcel

2022

Preprint

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“…While EHT observations may be successfully reproduced with a Kerr black hole supplied within general relativistic magnetic-hydrodynamical (GRMHD) simulations of the accretion flow [35], many works in the literature have sought for modifications to GR canonical black holes via addition of new fields [36][37][38][39][40][41][42] and hairy black holes [43,44], horizonless compact objects such as naked singularities [45,46], black bounces [47][48][49], boson stars [50][51][52][53][54], thin-shell [55] rotating [56] and asymmetric wormholes [57,58] and other objects [9,59]. Images of modified black holes beyond GR have been also considered: Gauss-Bonnet [60], asymptotic safety [61], noncommutative geometry [62], Einstein-AEther [63], Horndeski theory [64,65], quadratic gravity [66], or braneworlds [67], to mention a few.…”

Section: Shadow and Photon Ring Observationsmentioning

confidence: 99%

Shadows and photon rings of regular black holes and geonic horizonless compact objects

Olmo

Rosa

Rubiera-García

et al. 2023

Class. Quantum Grav.

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The optical appearance of a body compact enough to feature an unstable bound orbit, when surrounded by an accretion disk, is expected to be dominated by a luminous ring of radiation enclosing a central brightness depression typically known as the shadow. Despite observational limitations, the rough details of this picture have been now confirmed by the results of the EHT Collaboration on the imaging of the M87 and Milky Way supermassive central objects. However, the precise characterization of both features - ring and shadow - depends on the interaction between the background geometry and the accretion disk, thus being a fertile playground to test our theories on the nature of compact objects and the gravitational field itself in the strong-field regime. In this work we use both features in order to test a continuous family of solutions interpolating between regular black holes and horizonless compact objects, which arise within the Eddington-inspired Born-Infeld theory of gravity, a viable extension of Einstein's General Relativity (GR). To this end we consider seven distinctive classes of such configurations (five black holes and two traversable wormholes) and study their optical appearances under illumination by a geometrically and optically thin accretion disk, emitting monochromatically with three analytic intensity profiles previously suggested in the literature. We build such images and consider the sub-ring structure created by light rays crossing the disk more than once and existing on top of the main ring of radiation. We discuss in detail the modifications as compared to their GR counterparts, the Lyapunov exponents of unstable nearly-bound orbits, as well as the differences between black hole and traversable wormholes for the three intensity profiles. In addition we use the claim by the EHT Collaboration on the radius of the bright ring acting (under proper calibrations) as a proxy for the radius of the shadow itself to explore the parameter space of our solutions compatible with such a result.

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“…Such photon rings are a trademark of a given geometry, thus potentially harbouring a way to make robust tests of the Kerr hypothesis [30][31][32][33]. While EHT observations may be successfully reproduced with a Kerr black hole supplied within General Relativistic Magnetic-Hydrodynamical (GRMHD) simulations of an accretion disk model [34], many works in the literature have sought for modifications to GR canonical black holes via addition of new fields [35][36][37][38][39] and hairy black holes [40,41], horizonless compact objects such as naked singularities [42,43], black bounces [44,45], boson stars [46][47][48][49], rotating [50] and asymmetric wormholes [51,52], as well as modified black holes beyond GR within Gauss-Bonnet [53], asymptotic safety [54], noncommutative geometry [55], Einstein-AEther [56], Horndeski theory [57,58], quadratic gravity [59], or braneworlds [60], to mention a few.…”

Section: Shadow and Photon Ring Observationsmentioning

confidence: 99%

Shadows and photon rings of regular black holes and geonic horizonless compact objects

Olmo¹,

Rosa²,

Rubiera-García³

et al. 2023

Preprint

View full text Add to dashboard Cite

The optical appearance of a body compact enough to posses an unstable bound orbit, when surrounded by an accretion disk, is expected to be dominated by a luminous ring of radiation enclosing a central brightness depression known as the shadow, a picture fully backed up by the recent results of the EHT Collaboration. The characterization of both features -ring and shadowdepends on the interaction between the background geometry and the accretion disk, thus being a fertile playground to test our theories on the nature of compact objects and the gravitational field itself in the strong-field regime. In this work we use both features in order to test a continuous family of solutions interpolating between regular black holes and horizonless compact objects, which arise within the Eddington-inspired Born-Infeld theory of gravity, a viable extension of Einstein's General Relativity (GR). To this end we consider seven distinctive classes of such configurations (five black holes and two traversable wormholes) and study their optical appearances under illumination by a geometrically and optically thin accretion disk, emitting monochromatically with three analytic intensity profiles previously suggested in the literature. We build such images and consider the sub-ring structure created by light rays crossing the disk more than once and existing on top of the main ring of radiation. We discuss in detail the modifications as compared to their GR counterparts, the Lyapunov exponents of nearly unstable orbits, as well as the differences between black hole and traversable wormholes for the three intensity profiles. In addition we consider the properties of the shadow region and link them to the calibrated expectations by the EHT Collaboration. I. INTRODUCTIONA. Multimessenger quantum gravity era

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Probing Quadratic Gravity with the Event Horizon Telescope

Cited by 8 publications

References 61 publications

New black hole solutions with a dynamical traceless nonmetricity tensor in Metric-Affine Gravity

New black hole solutions with a dynamical traceless nonmetricity tensor in Metric-Affine Gravity

Shadows and photon rings of regular black holes and geonic horizonless compact objects

Shadows and photon rings of regular black holes and geonic horizonless compact objects

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