How to hunt for a black hole with a telescope the size of Earth

Castelvecchi, Davide

doi:10.1038/543478a

Cited by 9 publications

(12 citation statements)

References 5 publications

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“…We can observe that the analytical Regge pole approximations permit us to reproduce with very good agreement both the glory cross section and a large part of the orbiting cross section. It is moreover surprising to note that, by considering analytical Regge pole sums involving a large number of terms, we are able to describe the cross sections in a wide range of scattering angles despite the inaccuracy of the approximations (42) and (44) for the higher Regge poles (see Fig. 18 where we have considered the case of the scalar field at 2M ω = 6).…”

Section: Results and Commentsmentioning

confidence: 99%

“…The scalar cross section of a Schwarzschild BH for 2M ω = 6. We compare the exact result with the glory formula and with that obtained from the analytical Regge pole approximation where we sum over a large number of terms despite the inaccuracy of the approximations (42) and (44) for the higher Regge poles. This is really surprising and certainly due to the fact that BHs are very particular physical objects.…”

Section: Discussionmentioning

confidence: 99%

“…By extending to Regge poles the calculations which have permitted to Dolan and Ottewill to derive an analytical expression for the QNM excitation factors [57], we have obtained [47] By inserting now the approximations (42)-(43) for the Regge poles and (44)-(45) for the residues into the Regge pole sum (28) for the scalar field and into the Regge pole sum (40) for the electromagnetic field, we have at our disposal analytical approximations for the scattering cross sections associated with these two fields which are formally valid for 2M ω → +∞. It should be however noted that the Regge pole sums considered can only involve a small number of terms because the approximations (42) and (44) are accurate only for the lowest Regge poles. As a consequence, from a theoretical point of view, our analytical Regge pole approximations cannot describe the cross sections for small scattering angles.…”

Section: B Analytical Regge Pole Approximations Of Scattering Amplitmentioning

confidence: 99%

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Regge pole description of scattering of scalar and electromagnetic waves by a Schwarzschild black hole

Folacci

Hadj

2019

Phys. Rev. D

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We revisit the problem of scalar and electromagnetic waves impinging upon a Schwarzschild black hole from complex angular momentum techniques. We focus more particularly on the associated differential scattering cross sections. We derive an exact representation of the corresponding scattering amplitudes by replacing the discrete sum over integer values of the angular momentum which defines their partial wave expansions by a background integral in the complex angular momentum plane plus a sum over the Regge poles of the S-matrix involving the associated residues. We show that, surprisingly, the background integral is numerically negligible for intermediate and high frequencies and, as a consequence, that the cross sections can be reconstructed in terms of Regge poles with very good agreement. We show in particular that, for large values of the scattering angle, a small number of Regge poles permits us to describe the black hole glory and that, by increasing the number of Regge poles, we can reconstruct very efficiently the differential scattering cross sections for small and intermediate scattering angles and therefore describe the orbiting oscillations. In fact, in the short-wavelength regime, the sum over Regge poles allows us to extract by resummation the information encoded in the partial wave expansion defining a scattering amplitude and, moreover, to overcome the difficulties linked to its lack of convergence due to the long-range nature of the fields propagating on the black hole. As a consequence, from asymptotic expressions for the lowest Regge poles and the associated residues based on the correspondence Regge poles -"surface waves" propagating close to the photon sphere, we can provide an analytical approximation describing both the black hole glory and a large part of the orbiting oscillations. We finally discuss the role of the background integral for low frequencies.CONTENTS

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Section: Results and Commentsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: B Analytical Regge Pole Approximations Of Scattering Amplitmentioning

confidence: 99%

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Regge pole description of scattering of scalar and electromagnetic waves by a Schwarzschild black hole

Folacci

Hadj

2019

Phys. Rev. D

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“…We also expect the X-ray polarization measurements for Sgr A * . Finally, we hope that our model is helpful for the Event Horizon Telescope (EHT) project in the future (Chael et al 2016;Castelvecchi 2017).…”

Section: Discussionmentioning

confidence: 99%

Synchrotron Polarization of Relativistic Thermal Electrons

Mao¹,

Wang²

2018

ApJ

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Relativistic electrons accelerated by both the first-order and the second-order Fermi accelerations in some synchrotron sources have a hybrid shape of thermal and nonthermal energy distribution. This particle acceleration result is supported by some recent numerical simulations. We calculate the synchrotron polarization by applying this electron energy distribution. The polarization degrees in the cases of active galactic nucleus (AGN) jets and gamma-ray bursts (GRBs) are given as examples. The possible application for the polarization study of Sgr A * is also mentioned. We finally suggest high-energy polarization measurements for these synchrotron sources to test our results.

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“…X-ray binary systems require complicated models to describe atomic processes [14], which makes it hard to extract the information of horizons. The Event Horizon Telescope is a telescope network that observes astronomical objects near supermassive black hole horizons directly [15]. In contrast, we propose an alternative method to extract the physics of horizons through observing binary black-hole merger by gravitational waves.…”

Section: Introductionmentioning

confidence: 99%

Constraining black hole horizon effects by LIGO-Virgo detections of inspiralling binary black holes

Lai

2018

Phys. Rev. D

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General relativity predicts mass and spin growth of an inspiralling black hole due to an energy-momentum flux flowing through the black-hole horizon. The leading-order terms of this horizon flux introduce 2.5 and 3.5 post-Newtonian corrections to inspiral motions of binary black holes. The corrections may be measurable by gravitational waves detectors. Since the proper improvements to general relativity is still a mystery, it is possible that the true modified gravity theory introduces negligible direct corrections to the geodesics of test masses, while near horizon corrections are observable. We introduce a parameterization to describe arbitrary mass and spin growth of inspiralling black holes. Comparing signals of gravitational waves and a waveform model with parameterized horizon flux corrections, deviations from general relativity can be constrained. We simulate a set of gravitational waves signals following an astrophysical distribution with horizon flux modifications. Then, we perform a Bayesian analysis to obtain the expected constraints from the simulated response of the Advanced LIGO-Virgo detector network to the simulated signals. We show that the constraint can be improved by stacking multiple detections. The constraints of modified horizon flux can be used to test a specific class of modified gravity theories which predict dominant corrections near black-hole horizons over other types of corrections to general relativity. To support Hawking's area theorem at 90% confidence level, over 10000 LIGO-Virgo detections are required. Within the lifetime of LIGO and Einstein Telescope, a future ground-based gravitational wave detector, near horizon corrections of modified gravity theories are potentially detectable if one of the modified gravity theory is true and the theory predicts a strong correction. arXiv:1807.01840v3 [gr-qc]

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How to hunt for a black hole with a telescope the size of Earth

Cited by 9 publications

References 5 publications

Regge pole description of scattering of scalar and electromagnetic waves by a Schwarzschild black hole

Regge pole description of scattering of scalar and electromagnetic waves by a Schwarzschild black hole

Synchrotron Polarization of Relativistic Thermal Electrons

Constraining black hole horizon effects by LIGO-Virgo detections of inspiralling binary black holes

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