664 citations · 3.3k across the 54 of their papers we have counts for
49 papers · 1 filter
Gravitational lensing in Brill spacetimes
Mourad Halla, Volker Perlick
We consider the Brill metric which is an electrovacuum solution to Einstein's field equation. It depends on three parameters, a mass parameter , a NUT parameter and a charge…
Light propagation in a plasma on an axially symmetric and stationary spacetime: Separability of the Hamilton-Jacobi equation and shadow
Barbora Bezdekova, Volker Perlick, Jiri Bicak
The properties of light rays around compact objects surrounded by a plasma are affected by both strong gravitational fields described by a general-relativistic spacetime and by a d…
Photon sphere and shadow of a time-dependent black hole described by a Vaidya metric
Jay Solanki, Volker Perlick
In this paper we derive exact analytical formulas for the evolution of the photon sphere and for the angular radius of the shadow in a special Vaidya spacetime. The Vaidya metric d…
A Morse-theoretical analysis of lensing in wormhole spacetimes
Mourad Halla, Volker Perlick
We consider a class of stationary and axisymmetric wormhole spacetimes that is closely related to, but not identical with, the class of Teo wormholes. We fix a point (observati…
Calculating black hole shadows: Review of analytical studies
Volker Perlick, Oleg Yu. Tsupko
In this article, we provide a review of the current state of the research of the black hole shadow, focusing on analytical (as opposed to numerical and observational) studies. We s…
Geometrically thick tori around compact objects with a quadrupole moment
Jan-Menno Memmen, Volker Perlick
We study geometrically thick perfect-fluid tori with constant specific angular momentum, so-called "Polish doughnuts", orbiting deformed compact objects with a quadrupole moment. M…
Lightlike Geodesics and Gravitational Lensing in the Spacetime of an Accelerating Black Hole
Torben C. Frost, Volker Perlick
The C-metric is a solution to Einstein's vacuum field equation that describes an accelerating black hole. In this paper we discuss the propagation of light rays and the resulting l…
Application of the Gauss-Bonnet theorem to lensing in the NUT metric
Mourad Halla, Volker Perlick
We show with the help of Fermat's principle that every lightlike geodesic in the NUT metric projects to a geodesic of a two-dimensional Riemannian metric which we call the optical…
Aschenbach effect for spinning particles in Kerr spacetime
Jafar Khodagholizadeh, Volker Perlick, Ali Vahedi
The orbital velocity profile of circular timelike geodesics in the equatorial plane of a Kerr black hole has a non-monotonic radial behavior, provided that the spin parameter o…
Shadow of black holes at local and cosmological distances
G. S. Bisnovatyi-Kogan, O. Yu. Tsupko, V. Perlick
A brief illustrative discussion of the shadows of black holes at local and cosmological distances is presented. Starting from definition of the term and discussion of recent observ…
Redshift in Finsler spacetimes
Wolfgang Hasse, Volker Perlick
We derive and discuss a general redshift formula in Finsler spacetimes. The condition for the existence of a redshift potential is worked out. The results are illustrated with two…
Effects of non-linear vacuum electrodynamics on the polarization plane of light
Volker Perlick, Claus Lämmerzahl, Alfredo Macias
We consider the Pleba{ń}ski class of nonlinear theories of vacuum electrodynamics, i.e., Lagrangian theories that are Lorentz invariant and gauge invariant. Our main goal is to der…
Black hole shadow in an expanding universe with a cosmological constant
Volker Perlick, Oleg Yu. Tsupko, Gennady S. Bisnovatyi-Kogan
We analytically investigate the influence of a cosmic expansion on the shadow of the Schwarzschild black hole. We suppose that the expansion is driven by a cosmological constant on…
Finsler geometry as a model for relativistic gravity
Claus Lämmerzahl, Volker Perlick
We give an overview on the status and on the perspectives of Finsler gravity, beginning with a discussion of various motivations for considering a Finslerian modification of Genera…
The shadow of a collapsing dark star
Stefanie Schneider, Volker Perlick
The shadow of a black hole is usually calculated, either analytically or numerically, on the assumption that the black hole is eternal, i.e., that it existed for all time. Here we…
Bose-Einstein Condensates in Charged Black-Hole Spacetimes
Elías Castellanos, Juan Carlos Degollado, Claus Lämmerzahl +2
We analyze Bose-Einstein condensates on three types of spherically symmetric and static charged black-hole spacetimes: The Reissner-Nordström spacetime, Hoffmann's Born-Infeld blac…
Sachs equations for light bundles in a cold plasma
Karen Schulze-Koops, Volker Perlick, Dominik J. Schwarz
We study the propagation of light bundles in non-empty spacetime, as most of the Universe is filled by baryonic matter in the form of a (dilute) plasma. Here we restrict to the cas…
Light propagation in a plasma on Kerr spacetime: Separation of the Hamilton-Jacobi equation and calculation of the shadow
Volker Perlick, Oleg Yu. Tsupko
We consider light propagation in a non-magnetized pressureless plasma around a Kerr black hole. We find the necessary and sufficient condition the plasma electron density has to sa…
Definition of the relativistic geoid in terms of isochronometric surfaces
Dennis Philipp, Volker Perlick, Dirk Puetzfeld +2
We present a definition of the geoid that is based on the formalism of general relativity without approximations; i.e. it allows for arbitrarily strong gravitational fields. For th…
Circular motion in NUT space-time
Paul Jefremov, Volker Perlick
We consider circular motion in the NUT (Newman-Unti-Tamburino) space-time. Among other things, we determine the location of circular time-like geodesic orbits, in particular of the…
On causality in nonlinear vacuum electrodynamics of the Plebański class
Gerold O. Schellstede, Volker Perlick, Claus Lämmerzahl
We investigate the Plebański class of electrodynamical theories, i.e., theories of nonlinear vacuum electrodynamics that derive from a Lorentz-invariant Lagrangian (or Hamiltonian)…
On geodesic deviation in Schwarzschild spacetime
Dennis Philipp, Volker Perlick, Claus Laemmerzahl +1
For metrology, geodesy and gravimetry in space, satellite based instruments and measurement techniques are used and the orbits of the satellites as well as possible deviations betw…
Influence of a plasma on the shadow of a spherically symmetric black hole
Volker Perlick, Oleg Yu. Tsupko, Gennady S. Bisnovatyi-Kogan
We analytically calculate the influence of a plasma on the shadow of a black hole (or of another compact object). We restrict to spherically symmetric and static situations, where…
Isofrequency pairing of spinning particles in Schwarzschild-de Sitter spacetime
Daniela Kunst, Volker Perlick, Claus Lämmerzahl
It has been established in Schwarzschild spacetime (and more generally in Kerr spacetime) that pairs of geometrically different timelike geodesics with the same radial and azimutha…