相关论文: Velocity measurements in General Relativity revisi…

In this essay, we argue that certain aspects of the measurement require revision in Quantum Gravity. Using entropic arguments, we propose that the number of measurement outcomes and the accuracy (or the range) of the measurement are limited…

A nonrelativistic particle released from rest at the edge of a ball of uniform charge density or mass density oscillates with simple harmonic motion. We consider the relativistic generalizations of these situations where the particle can…

A new way to implement the causality condition on the event horizon of black holes is discovered. The metric of a black hole is shown to be a function of the complex-valued gravitational radius r_g => r_g + i0. The relation between this…

The impressive images from the Event Horizon Telescope sharpen the conflict between our observations of gravitational phenomena and the principles of quantum mechanics. Two related scenarios for reconciling quantum mechanics with the…

We present techniques and methods for analyzing the dynamics of event horizons in numerically constructed spacetimes. There are three classes of analytical tools we have investigated. The first class consists of proper geometrical measures…

Horndeski gravity holds a special position as the most general extension of Einstein's theory of general relativity with a single scalar degree of freedom and second-order field equations. Because of these features, Horndeski gravity is an…

The Event Horizon Telescope (EHT), a global 230 GHz VLBI array, achieves an angular resolution of ${\approx} 20\,\mu{\rm as}$, sufficient to resolve the supermassive black hole Sagittarius A* (Sgr A*). This resolution may soon enable…

I discuss several general-relativistic effects that are likely to be of interest in the astrophysics of black holes and neutron stars

An attempt to answer the question 'Can we observe galaxies that recede faster than light ?' led to a re-examination of the notions of time, distance, velocity and redshift as they occur in newtonian physics, special relativity, general…

We consider general radially moving frames realized in the background of nonextremal black holes having causal structure similar to that of the Schwarzschild metric. In doing so, we generalize the Lema\^{\i}tre approach, constructing…

Working in a semi-classical setting, we consider solutions of the Einstein equations that exhibit light trapping in finite time according to distant observers. In spherical symmetry, we construct near-horizon quantities from the assumption…

We estimate the number of individual, fast-moving stars observable in globular clusters under the assumption that the clusters contain massive central black holes which follow the galactic black-hole mass vs. sigma relationship. We find…

The groundbreaking image of the black hole at the center of the M87 galaxy has raised questions at the intersection of observational astronomy and black hole physics. How well can the radius of a black hole shadow can be measured, and can…

General relativity predicts that clocks run more slowly near massive objects. The effect is small---a clock at sea level lags behind one 1000 m above sea level by only 9.4 ns/day. Here, we demonstrate that a measurement of this effect can…

Black holes have the peculiar and intriguing property of having an event horizon, a one-way membrane causally separating their internal region from the rest of the Universe. Today astrophysical observations provide some evidence for the…

Nowadays, the effect of infinite energy in the centre of mass frame due to near-horizon collisions attracts much attention.We show generality of the effect combining two seemingly completely different approaches based on properties of a…

Although General Relativity (GR) has been tested extensively in the weak gravity regime, similar tests in the strong gravity regime are still missing. In this paper we explore the possibility to use X-ray spectropolarimetric observations of…

The Advanced LIGO/Virgo interferometers have observed $\sim 100$ gravitational-wave transients enabling new questions to be answered about relativity, astrophysics, and cosmology. However, many of our current procedures for computing these…

We investigate Rindler's frame measurements. From its perspective, we found a geometric/gravitational interpretation of speed of light, mass and uncertainty principle. This can be interpreted as measurements of a black hole universal clock.…

We propose a new parametrization for testing the Kerr nature of astrophysical black hole candidates. The common approaches focus on the attempt to constrain possible deviations from the Kerr solution described by new terms in the metric.…