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Electromagnetic rotational superradiance
Bára, Václav ; Ledvinka, Tomáš (advisor) ; Kofroň, David (referee)
We show the scattering of electromagnetic radiation on a rotating cylinder and a rotating sphere using formalism of the vector spherical harmonics in this thesis. If a specific condition is satisfied then we can observe the rotational superradiance, phenomena originally discovered by Y. B. Zel'dovich in 1970s saying that the radiation can gain power by scattering on a rotating body. In this particular case there is an underlying principle of the rotational superradiance, the energy dissipation in the form of Joule heating created due to the induction of surface currents on the conductor. Superradiance can occur in the radiation scattering on the rotating black hole background, although there is no dissipation present. We summarize the results of scattering on the Kerr black hole from the literature, including an application called Black hole bomb, when the black hole is enclosed into a perfectly reflecting mirror. We show that for the lowest modes of the radiation at specific intervals the general relativity results can be approximated by scattering on the flat spacetime.
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Principles of gravitational-wave detection
Přeučil, Filip ; Ledvinka, Tomáš (advisor) ; Kofroň, David (referee)
In the present work we investigate the impact of weak gravitational wave in the linearized theory of gravity on a simple model of an interferometric gravitational wave detector, whose individual parts (mirrors, and electromagnetic field) are idealised by free test particles. After a necessary, fairly popularly conceived introduction to gravitational wave theory in the linearized gravity, the astrophysical sources of the gravitational waves, the possibilities of their detection and the principles of the detectors, we provide a mathematical survey of the indispensable parts of general relativity and of the linearized theory of gravity. After that, we finally deal with the model itself. In the linear approximation with respect to the perturbations, we solve the equations of motion of the individual components and derive the detector response to a gravitational wave. Finally, we present a few comments, including a proof of gauge invariance of the derived formula.
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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.
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Binary pulsars - astrophysical laboratories (not only) of theory of general relativity
Beňová, Zuzana ; Kofroň, David (advisor) ; Karas, Vladimír (referee)
Title: Binary pulsars - astrophysical laboratories of general relativity Author: Zuzana Beňová Department: Institute of Theoretical Physics Supervisor: Mgr. David Kofroň, PhD Supervisor's e-mail address: d.kofron@gmail.com The mail concern of this work are tests of relativistic theories of gravitation (mainly GR) that are made by employing compact double-pulsars. The first part is devoted to basic tests and effects of relativistic theories: gravitatio- nal redshift, orbital period decay due to the emission of gravitational waves, periastron shift, Shapiro effect and precession of rotation axis. A brief de- scription of pulsars (in general) and double-pulsars follows. We describe the orbital parameters and their post-Keplerian corrections. Finally, the theory is demonstrated on the unique double-pulsar PSR J037-3039 A/B which was discovered only 7 years ago. Keywords: relativistic theories, double pulsar, tests of GR
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