Constraining modified gravity theories with scalar fields using black-hole images

Abstract

We study a number of well-motivated theories of modified gravity with the common overarching theme that they predict the existence of compact objects such as black holes and wormholes endowed with scalar hair. We compute the shadow radius of the resulting compact objects and demonstrate that black hole images such as that of M87${}^{\ast }$ or the more recent SgrA${}^{\ast }$ by the Einstein Horizon Telescope (EHT) collaboration may provide a powerful way to constrain deviations of the metric functions from what is expected from general relativity (GR) solutions. We focus our attention on Einstein-scalar-Gauss-Bonnet (EsGB) theory with three well motivated couplings, including the dilatonic and $Z_2$ symmetric cases. We then analyze the shadow radius of black holes in the contest of the spontaneous scalarization scenario within EsGB theory with an additional coupling to the Ricci scalar (EsRGB). Finally, we turn our attention to spontaneous scalarization in the Einstein-Maxwell-Scalar (EMS) theory and demonstrate the impact of the parameters on the black hole shadow. Our results show that black hole imaging is an important tool for constraining black holes with scalar hair and for some part of the parameter space, black holes solutions with scalar hair may be marginally favoured compared to solutions of GR.

17 pages, 9 figures, 2 tables

References in corpus (43)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• The Confrontation between General Relativity and Experiment
• First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way
• First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole
• First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
• First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
• First M87 Event Horizon Telescope Results. II. Array and Instrumentation
• Dark Energy after GW170817: dead ends and the road ahead
• First M87 Event Horizon Telescope Results. III. Data Processing and Calibration
• Strong constraints on cosmological gravity from GW170817 and GRB 170817A
• Implications of the Neutron Star Merger GW170817 for Cosmological Scalar-Tensor Theories
• First Sagittarius A* Event Horizon Telescope Results. VI: Testing the Black Hole Metric
• Wormhole geometries in f(R) modified theories of gravity
• Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole
• First Sagittarius A* Event Horizon Telescope Results. V. Testing Astrophysical Models of the Galactic Center Black Hole
• Relativistic images of Schwarzschild black hole lensing
• First Sagittarius A* Event Horizon Telescope Results. III: Imaging of the Galactic Center Supermassive Black Hole
• Time delay and magnification centroid due to gravitational lensing by black holes and naked singularities
• A Metric for Rapidly Spinning Black Holes Suitable for Strong-Field Tests of the No-Hair Theorem
• First Sagittarius A* Event Horizon Telescope Results. II. EHT and Multi-wavelength Observations, Data Processing, and Calibration
• First Sagittarius A* Event Horizon Telescope Results. IV. Variability, Morphology, and Black Hole Mass
• Constraints on black-hole charges with the 2017 EHT observations of M87*
• Gravitational Test Beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole
• Rotating Black Holes in Dilatonic Einstein-Gauss-Bonnet Theory
• Spontaneously scalarised Kerr black holes
• Are black holes in alternative theories serious astrophysical candidates? The case for Einstein-Dilaton-Gauss-Bonnet black holes
• Black holes with scalar hair in light of the Event Horizon Telescope
• Strong-field Gravity Tests with the Double Pulsar
• Einstein-Gauss-Bonnet traversable wormholes satisfying the weak energy condition
• Wormhole geometries supported by a nonminimal curvature-matter coupling
• Swampland Implications of GW170817-compatible Einstein-Gauss-Bonnet Gravity
• Self-interactions and Spontaneous Black Hole Scalarization
• Black Holes in the Dilatonic Einstein-Gauss-Bonnet Theory in Various Dimensions I -- Asymptotically Flat Black Holes --
• Novel Black-Hole Solutions in Einstein-Scalar-Gauss-Bonnet Theories with a Cosmological Constant
• Lorentzian wormholes in Eddington-inspired Born-Infeld gravity
• A Refined Einstein-Gauss-Bonnet Inflationary Theoretical Framework
• Gauss-Bonnet black holes with a massive scalar field
• Test of Einstein equivalence principle near the Galactic center supermassive black hole
• The onset of spontaneous scalarization in generalised scalar-tensor theories
• Properties of ultra-compact particle-like solutions in Einstein-scalar-Gauss-Bonnet theories
• Testing General Metric Theories of Gravity with Bursting Neutron Stars
• Wormhole solutions in $f(R)$ gravity theory for Chaplygin gas scenario

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• Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A${}^{\ast }$
• Testing the Speed of Gravity with Black Hole Ringdown
• Distinguishing black holes with and without spontaneous scalarization in Einstein-scalar-Gauss-Bonnet theories via optical features
• Mixed scalarization of charged black holes: from spontaneous to non-linear scalarization
• Circular geodesics in the field of double-charged dilatonic black holes
• Black hole photon ring beyond General Relativity: an integrable parametrization