National Repository of Grey Literature 71 records found  previous11 - 20nextend  jump to record: Search took 0.01 seconds. 
Solving test-particle equations of motion near a black hole
Ryston, Matěj ; Ledvinka, Tomáš (advisor) ; Suková, Petra (referee)
Bachelor thesis Matěj Ryston 2011/2012 Abstract in English This work aims to give a well-arranged summary of the description and solving the equations of motion of particles outside a black hole (a star) with emphasis on numerical solutions. For that purpose a summary of numerical methods for solving ordinary differential equations, together with a review and comparison of chosen methods, is given. In the second chapter follows a brief recall of the foundations of General Relativity as well as the description of the geometry of Schwarzschild solution of the Einstein equations. After that equations of motion are formulated. In conclusion, selected numerical methods are used on solving said equations of motion of a test particle or those describing bending of light rays in closeness to a black hole.
Numerical evolution of black-hole spacetimes
Khirnov, Anton ; Ledvinka, Tomáš (advisor) ; Palenzuela, Carlos (referee)
吀e so-called "trumpet" initial data has recently received mu挀 a琀ention as a potential candidate for the natural black hole initial data to be used in 3+1 numerical relativity simulations with 1+log foliation. In this work we first derive a variant of the maximal trumpet initial data that is made to move on the numerical grid by the means of a Lorentz boost and write a numerical code that constructs this boosted trumpet initial data. We also write a numerical code for calculating the Krets挀mann scalar from the 3+1 variables, to be used in analysing the data from our simulations. With the help of those two codes, we study the behaviour of the boosted trumpet initial data when evolved with the BSSN formulation of the Einstein equations, using 1+log slicing and the Γ-driver shi昀 condition.
Modeling the Mach's principle in the post-Minkowskian approximation to general relativity
Schmidt, Tibor ; Ledvinka, Tomáš (advisor) ; Kofroň, David (referee)
The aim of this thesis is the simulation of relativistic phenomena in post- Minkowskian approximation. In the introduction the terms of Mach principle and gravitomagnetism are presented. Afterwards the principles of numeric solution of ordinary differential equations are summarized. Consequently, we get acquainted with the first post-Minkowskian approximation in canonical formalism and with elementary examples of its use. In the next chapter the results of performed simulations of classical General Relativity tests are described. The last chapter is devoted to the simulation of gravitomagnetism and of the system of rotating particles.
Slowly rotating sources around static black holes
Čížek, Pavel ; Semerák, Oldřich (advisor) ; Ledvinka, Tomáš (referee)
In this thesis we study the possibility of perturbative solution of the Einstein equations in the case of stationary and axially symmetric metric. The method is motivated by the pursuit of describing the astrophysically important system of a black hole surrounded by a thin disc or a ring. A Schwarzschild black hole is thus considered as a central source, with a light and/or slowly rotating disc around. We show that the metric can be found in terms of perturbative expansions in relative disc mass or in inverted distance from the hole, and point out where problems occur. The approach can be applied to a disc "given in advance" as well as in the "self-consistent" case when the disc elements orbit on circular geodesics in the desired total eld. It can also be generalised to the discs composed of more dust components.
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
Solved Problems in Electromagnetism for Electronic Collection
Pošta, Petr ; Koupilová, Zdeňka (advisor) ; Ledvinka, Tomáš (referee)
This thesis is a follow-up to several bachelor and diploma theses which were dedicated to creating solved problems for Electronic Collection of Solved Problems in Electromagnetism. The first goal of this thesis was to make a short survey about electronic resources in electromagnetism, especially those which contain solved problems and provide open access to their contents. The second goal was to make a small collection of solved problems in this area which would be suitable for undergraduate students and which would fill in chapters with little amount of problems in the Electronic Collection. This Electronic Collection is openly accesible on the website of Department of Physics Education. Total of 30 solved problems have been made in this thesis, including hints, detailed solutions and suitable pictures. Methodical comments are also available for almost all problems.

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