Related papers: Is a photon ring invariably a closed structure?
Modelling of gravitational waves from binary black hole inspiral has played an important role in the recent observations of such signals. The late-stage ringdown phase of the gravitational waveform is often associated with the null particle…
The Kerr spacetime is symmetric with respect to a well-defined equatorial plane. When testing the equatorial reflection symmetry of an isolated black hole, one is at the same time testing the Kerr hypothesis in General Relativity. In this…
A distinct visual signature occurs in black holes that are surrounded by optically thin and geometrically thick emission regions. This signature is a sharp-edged dip in brightness that is coincident with the black-hole shadow, which is the…
We present the shape of the black hole shadow on the standard background screen as it is registered by the distant observer. The screen is an infinite plane, emitting the quanta uniformly distributed to a hemisphere. The source of emission…
The motion of photons around black holes determines the shape of shadow and match the ringdown properties of a perturbed black hole. Observations of shadows and ringdown waveforms will reveal the nature of black holes. In this paper, we…
Motivated by the prospect of measuring a black hole photon ring, in previous work we explored the interferometric signature produced by a bright, narrow curve in the sky. Interferometric observations of such a curve measure its "projected…
We study the scattering of infrared light by small dielectric core-shell particles taking a sapphire sphere with a CaO core as an example. The extinction efficiency of such a particle shows two intense series of resonances attached,…
Light interaction with rotating nanostructures gives rise to phenemona as varied as optical torques and quantum friction. Here we reveal that circular dichroism of rotating optically-isotropic particles has an unexpectedly strong dependence…
Black hole images are theoretically predicted (under mild astrophysical assumptions) to display a stack of lensed "photon rings" that carry information about the underlying spacetime geometry. Despite vigorous efforts, no such ring has been…
In Einstein-{\AE}ther theory, the Lorentz symmetry is locally broken in the high-energy regime due to the presence of the{\AE}ther field. This shall leave significant imprint on astronomical observation. In this paper, we investigate the…
The 2017 Event Horizon Telescope (EHT) observations of M87* detected a ring-shaped feature $\sim40\mu$as in diameter, consistent with the event horizon scale of a black hole of the expected mass. The thickness of this ring, however, proved…
The Event Horizon Telescope image of the supermassive black hole in the galaxy M87 is dominated by a bright, unresolved ring. General relativity predicts that embedded within this image lies a thin "photon ring," which is composed of an…
We study scattering of polarized light by a rotating (Kerr) black hole of the mass M and the angular momentum J. In order to keep trace of the polarization dependence of photon trajectories one can use the following dimensionless parameter:…
Closed photon orbits around isolated black holes are related to important aspects of black hole physics, such as strong lensing, absorption cross section of null particles and the way that black holes relax through quasinormal ringing. When…
In this talk I briefly explain the concept of the structure function of a photon (the best known boson). Then I review some of the current experimental evidence which confirms the existence of `strong' interactions of photon suggested by…
The $n=1$ photon ring is a full image of the astrophysical source around a black hole, produced by photons that execute $n\approx1$ half-orbit around the event horizon on their way to an observer. The Black Hole Explorer (BHEX) is a…
We have studied the polarized image of an equatorial emitting ring around a rotating black hole surrounded by a cold dark matter (CDM) halo. Results show that the CDM halo density has the similar effects of the halo's characteristic radius…
In this study, we analyze the observational images of a Konoplya-Zhidenko rotating non-Kerr black hole, wherein a thin accretion disk, serving as the sole background light source, is situated on the equatorial plane of the black hole. The…
Shine a flashlight on a black hole, and one is greeted with the return of a series of concentric rings of light. For a point source of light, and for perfect alignment of the lens, source, and observer, the rings are of infinite brightness…
General relativity predicts that images of optically thin accretion flows around black holes should generically have a ``photon ring,'' composed of a series of increasingly sharp subrings that correspond to increasingly strongly lensed…