|
|
Parameterization of the Kerr solution
Miškovský, David ; Švarc, Robert (advisor) ; Scholtz, Martin (referee)
In this thesis we are exploring basic properties of the Kerr solution using se- veral coordinate systems. Later on, we are deriving general metric form of the spacetime foliated by null hypersurfaces. Employing the formalism of optical sca- lars we shall see, that geometry of a such a spacetime is non-twisting, that is it admits existence of a non-twisting affinely parametrized null geodesic congru- ence. Subsequently, we are trying to express the Kerr solution in the form of non-twisting coordinates. This form would have many applications e.g. in forma- lism of weakly isolated horizons (WHIs) for use in more realistic astrophysical models of black holes.
|
|
|
Space-times of ring sources
Pešta, Milan ; Semerák, Oldřich (advisor) ; Ledvinka, Tomáš (referee)
Marginally outer-trapped surfaces (MOTSs) are found for a family of space-like hypersurfaces described by the Brill-Lindquist initial data. These hypersurfaces contain a singular ring characterized by its radius, mass and charge. Due to the ring character of the singularity, these surfaces are natural candidates for MOTSs with toroidal topology. By adjusting and employing the numerical method of geodesics, we indeed localize MOTSs of both spherical and toroidal topology, and compare the results with those obtained previously by Jaramillo & Lousto.
|
|
|
Geodesic chaos in a perturbed Schwarzschild field
Polcar, Lukáš ; Semerák, Oldřich (advisor) ; Kopáček, Ondřej (referee)
We study the dynamics of time-like geodesics in the field of black holes perturbed by a circular ring or disc, restricting to static and axisymmetric class of space-times. Two analytical methods are tested which do not require solving the equations of motion: (i) the so-called geometric criterion of chaos based on eigenvalues of the Riemann tensor, and (ii) the method of Melnikov which detects the chaotic layer arising by break-up of a homoclinic orbit. Predictions of both methods are compared with numerical results in order to learn how accurate and reliable they are.
|
|
|
Rotating thin disc around a Schwarzschild black hole: properties of perturbative solution
Kotlařík, Petr ; Semerák, Oldřich (advisor) ; Ledvinka, Tomáš (referee)
In 1974, Will presented a solution for the perturbation of a Schwarzschild black hole due to a slowly rotating and light thin disc given in terms of a multipole expansion of the perturbation series. In a recently submitted paper, P. Čížek and O. Semerák generalized this procedure to the perturbation by a slowly rotating finite thin disc, using closed forms of Green functions rather than the multipole expansion. The method is illustrated there, in the first perturbation order, on the constant-density disc. In this thesis, we summarize, check and plot some of the obtained properties, and show how the presence of the disc changes the geometry of a horizon and the position of significant circular orbits. 1
|
|
|
Fields of current loops around black holes
Vlasáková, Zuzana ; Semerák, Oldřich (advisor) ; Svítek, Otakar (referee)
The magnetic field of a test circular current loop placed symmetrically around a Schwarzschild black hole has been determined several times in the literature and solutions has been expressed by different formulas. We compare these formulas analytically as well as numerically, and show, in particular, how they behave on the symmetry axis, in the equatorial plane and on the horizon. The problem is relevant for modelling accretion discs around black holes.
|
|
|
Space-times with toroidal horizons
Pešta, Milan ; Semerák, Oldřich (advisor) ; Ledvinka, Tomáš (referee)
Basic results of the uniqueness theorems and the topological-censorship theorem are presented. Properties of the well-known solution of Einstein's equations with a toroidal event horizon are examined and one of possible visualizations of the coordinate system that helps to better understand the behaviour of various invariants in the vicinity of the singularity is suggested. Apart from this solution, two solutions with a ring singularity are introduced as potential candidates for space-times with toroidal horizons whose properties are interpreted intuitively using the toroidal or Weyl coordinate systems. Last part is devoted to apparent horizons of the considered solutions and the differential equation for the apparent horizon of an arbitrary solution of the Weyl class is derived. The numerical solution of this equation is not presented.
|
|
|
Geodesics in the field of a perturbed black hole: where appears chaos?
Polcar, Lukáš ; Semerák, Oldřich (advisor) ; Suková, Petra (referee)
It is widely known that the motion around Schwarzshild black hole is completely integrable. However, after adding a disc or a ring one of the symmetries of the system is broken and the motion may become chaotic for some values of parameters. The aim of this thesis is to identify where appears chaos in static, axially symmetric spacetime by using the geometrical method based on the geodesic deviation equation. Is it possible to predict chaotic behaviour in general relativity solely from local geometrical properties of spacetime, without explicitly solving the geodesic equation? Powered by TCPDF (www.tcpdf.org)
|
|
|
Possibilities of teaching/learning general relativity at elementary level
Ryston, Matěj ; Dvořák, Leoš (advisor) ; Žák, Vojtěch (referee)
This thesis deals with an elementary introduction to general relativity on a level understandable by secondary school students and graduates. It contains a review of available literature including its approach to the introductory level of relativity, a study text covering the necessary parts of classical mechanics, special relativity and subsequently basic ideas and conclusions of general relativity. A didactical analysis of the study text is also part of the thesis. The text presumes only basic knowledge of secondary school physics (mostly mechanics), therefore it is suitable for a wide range of readers amongst secondary school students and graduates. It can also be useful as a study material for secondary school teachers, who wish to enrich their teaching with more modern chapters of physics.
|
|
|
Symmetries of systems in spaces related to high-dimensional black hole spacetime
Kolář, Ivan ; Krtouš, Pavel (advisor) ; Kubizňák, David (referee)
In this work we study properties of the higher-dimensional generally rotating black hole space-time so-called Kerr-NUT-(A)dS and the related spaces with the same explicit and hidden symetries as the Kerr-NUT-(A)dS spacetime. First, we search commuta- tivity conditions for classical (charged) observables and their operator analogues, then we investigate a fulfilment of these conditions in the metioned spaces. We calculate the curvature of these spaces and solve the charged Hamilton-Jacobi and Klein-Gordon equations by the separation of the variables for an electromagnetic field, which pre- serves integrability of motion of a charged particle and mutual commutativity of the corresponding operators.
|
|
|
Spinning particles in algebraically special space-times
Šrámek, Milan ; Semerák, Oldřich (advisor) ; Krtouš, Pavel (referee)
Spinning-particle motion is studied, within the pole-dipole approximation, in algebraically special space-times of type N, III and D. The spin-curvature interaction is analysed for the Pirani and Tulczyjew spin supplementary conditions; for N and D types, the condition is related to a relative acceleration of two near observers separated in the direction of particle's spin. For Tulczyjew's condition, the momentum-velocity relation is also studied as well as its consequences for the spin-curvature interaction. Finally, the type of motion is mentioned for which both the supplementary conditions considered are equivalent.
|
guest ::
