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Universal solutions in gravity, electrodynamics and nonabelian gauge theories
Kuchynka, Martin ; Pravdová, Alena (advisor) ; Hervik, Sigbjorn (referee) ; Švarc, Robert (referee)
The presented thesis spans over a number of related topics with a com- mon theme - the so-called universality. Classical fields exhibiting this property serve as exact solutions to virtually any higher-order theory irrespective of the particular form of the field equations, being thus of particular interest in ef- fective field theories. The aim of this work is to study various aspects of such solutions in the context of gravity, electrodynamics, as well as more general nonabelian gauge theories. The results are concentrated in four chapters, the first of which is devoted to what we call the almost universal spacetimes. Due to their nice curvature properties, these spacetimes provide an efficient method for simplifying and solving the field equations of higher-order gravity theories. We illustrate this feature of almost universal metrics by finding new vacuum solutions to quadratic gravity and six-dimensional conformal gravity. In the second chapter, we shift our attention towards electrodynamics. Following up on recent results on universal electromagnetic fields, we deal with Einstein- Maxwell fields which simultaneously solve also any higher-order modification of the Einstein-Maxwell theory. In particular, we identify solutions with this remarkable property as plane-fronted gravitational and...
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Effects of additional scalar decaplet in the RG evolution of the running gauge couplings in the minimal SO(10) grand unified theory
Press, Pavel ; Malinský, Michal (advisor) ; Sousa da Fonseca, Renato Miguel (referee)
Effects of additional scalar decaplet in the RG evolution of the running gauge couplings in the minimal SO(10) grand unified theory Pavel Press Abstract We begin the thesis with the fundamentals of Lie groups and algebras. Then we introduce basic concepts regarding classical field theory and gauge theory. We formulate the Goldstone theorem and with it we describe the Higgs mechanism. We quantize the classical fields and outline the calculations within the quantum field theory. Using the renormalization procedure we derive the equations for the running coupling of a general gauge theory. We calculate the running gauge couplings in the Standard model and motivate theories beyond it. In particular, we will study the Grand Unified Theories. We discuss a specific Higgs sector with a 45 ⊕ 126 Higgs field. In order to have a more realistic theory we add a scalar Higgs decaplet and study its effects on the running couplings. Finally we discuss the implications of the decaplet for the proton decay. Keywords Quantum field theory, gauge field theory, running couplings, grand unification, proton decay 1
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Aspects of renormalization of spontaneously broken gauge theories
Hudec, Matěj ; Malinský, Michal (advisor) ; Beneš, Petr (referee)
In this thesis, we use the Coleman-Weinberg effective potential for computing the radiative corrections to scalar masses in six simple models of the quantum field theory. We probe, for example, the theory of two scalar fields, simple generalizations of the Abelian Higgs model or some classic extensions of the Standard Model. A common feature of all the theories considered is the existence of (at least) two mass scales different in order of magnitude. Being motivated by the hierarchy problem, we study mainly the sensitivity of light scalar masses on the radiative corrections induced by the heavy fields in relevant Feynman loops. We demonstrate that while the masses of scalars with zero VEV obtain corrections proportional to the masses of the heavy fields, in theories with the spontaneous symmetry breakdown is the Higgs mass always governed by the corresponding ordering parameter, i.e., by its vacuum expectation value. For the Standard Model, understood as an effective field theory, this implies that the Higgs boson mass is as stable with respect to the effects of possible new physics on very high energies as the masses of the leptons, quarks, W and Z bosons. Powered by TCPDF (www.tcpdf.org)
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Higher spin theories in three dimensions
Flandera, Aleš ; Raeymaekers, Joris (advisor) ; Procházka, Tomáš (referee)
In this thesis the theory of general relativity is rewritten into a gauge Chern- Simons theory. The vielbein formalism is used for this purpose. It is shown that the action of such a theory corresponds to the Einstein-Hilbert action. The most important properties of the Chern-Simons theory are investigated. However the aim is to extend this description of spin-2 particles to the higher spin ones. This is done through treating Lie algebra generators and their potentials. Properties of the spin-2 solution are discussed in this context. An example of higher spin solutions, so-called conical defects, is also given.
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