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Statistical aspects of nuclear collective dynamics
Macek, Michal ; Cejnar, Pavel (advisor) ; Kvasil, Jan (referee) ; Mareš, Jiří (referee)
The current PhD thesis presents a collection of selected articles related to the theoretical and numerical study of low-energy collective dynamics of atomic nuclei. The articles were published or recently submitted to international physics journals and were authored or co-authored by the author of the thesis. The eects in collective dynamics have been studied within the framework of two common models-the interacting boson model (IBM) and to a lesser extent the geometric collective model (GCM). The "statistical aspects" in the title relate predominantly to the interplay of ordered and chaotic behavior observed in properties of quantum eigenstates as well as in the classical limits of the models. The main attention was devoted to correlations between the measures of regularity/chaos and the presence of exact and approximate dynamical symmetries. An important subject of the studies were also the relationships between the properties of the classical and quantum solutions of the models both in the integrable regime as well as in the mixed regime containing elements of regularity and chaos simultaneously.
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JAWS Framework for Non-standard Applications
Ficek, Michal ; Cejnar, Pavel (advisor) ; Kryl, Rudolf (referee)
The JAWS application (www.freedomscienti c.com) is capable of allowing access of blind users to computer controls. Applications with graphical control elements that often substitute for standard controls of Microsoft Windows or applications that don't support full keyboard control have to be modi ed with JAWS scripting language to give out sounds and allow control of the sight impaired. This project describes creation of a script for speci c application and analyzes what parts of the script can be automatically generated. At the same time we introduce JAWS Framework - application with included users manual, technical documentation and discussion of solutions according to the speci fication of our project.
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Photon strength functions in 196Pt from two-step gamma cascade measurement
Kloc, Michal ; Krtička, Milan (advisor) ; Cejnar, Pavel (referee)
Photon strength functions (PSFs), using the statistical approach to a nuclear decay, seem to be a suitable tool for the description of the electromagnetic transitions in a nucleus. Since the early 50's, when PSFs were first introduced, a plenty of theoretical models were proposed however their validity is still a question. In this work the data from the measurement of so called Two step cascades in the nucleus 196Pt using the reaction 195Pt(n,gamma)196Pt are processed. The experiment was performed at the Nuclear Physics Institute ASCR in Řež near Prague. We assume that these experimental spectra contain important information on PSFs. Comparison of the processed data with a few Monte Carlo simulations is also a part of this thesis.
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Regular and chaotic collective motions of atomic nuclei
Hruška, Petr ; Cejnar, Pavel (advisor) ; Knapp, František (referee)
This thesis deals with quantum chaos in the geometric collective model of atomic nuclei (GCM). The rst and second chapters introduce the derivation and analysis of basic aspects of the GCM. Two ways of quantization are introduced for zero rotations of the nucleus. The rst one takes into account only the vibrational degrees of freedom and does not correspond to real nuclei. The second way reects both vibrational and rotational degrees of freedom and leads to the standard GCM. The third chapter includes analytical calculations of matrix elements of the GCM in the harmonic oscillator basis. Some measures of chaos are described in the fourth chapter, including the method based on Peres lattices. Numerical results for both quantization methods are presented in the form of Peres lattices, which are compared with some adopted results of other measures of chaos.
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Quantal and thermal phase transitions in atomic nuclei
Dvořák, Martin ; Cejnar, Pavel (advisor) ; Knapp, František (referee)
In this bachelor work phase transitions in atomic nuclei are studied. The main attention is paid to quantal phase transitions between nuclear ground states of different symmetry. First, the interacting boson model in its simplest version, IBM-1, is introduced. The correspondence between the IBM and the geometric model of nuclei is indicated and possible shapes of the nucleus in the ground state are introduced. In the next step, critical and degenerated critical points of the potential derived from the IBM-1 are investigated in detail, especially their dependence on parameter values of the potential. Degenerated critical points are classified using the catastrophe theory. The special values of potential parameters are found for which phase transitions of the first and second order occur. Finally, the possibility of substitution of the potential by canonical catastrophic functions in a vicinity of degenerated critical points is discussed.
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