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Exact spacetimes in modified theories of gravity
Karamazov, Michal ; Švarc, Robert (advisor)
In the review part of the thesis we summarize various modified theories of gravity, especially those that are characterized by additional curvature invariants in the Lagrangian density. Further, we review non-twisting geometries, especially their Kundt subclass. Finally, from the principle of least action we derive field equations for the case with the Lagrangian density corresponding to an arbitrary function of the curvature invariants. In the original part of the thesis we explicitly express particular components of the field equations for non-gyratonic Kundt geometry in generic quadratic gravity in arbitrary dimension. Then we discuss how this, in general fourth order, field equations restrict the Kundt metric in selected geome- trically privileged situations. We also analyse the special case of Gauss-Bonnet theory. 1
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Conformally related spacetimes
Knoška, Šimon ; Švarc, Robert (advisor) ; Scholtz, Martin (referee)
The main objective of this thesis is to investigate the possibility of creating Robinson-Trautman spacetimes from Kundt class of geometries. In the first chap- ter, properties of the Robinson-Trautman and Kundt geometries in arbitrary dimension are summarised. Natural coordinates adapted to the null spacetime foliation generated by non-twisting shear-free affinely parametrized null geodesic congruence are introduced. In the following chapter, general conformal trans- formation and specific conformal relation between the Robinson-Trautman and Kundt classes of spacetimes is discussed. Finally, attempts to find solutions to the field equations by employing this conformal relation in Einstein's theory of gravity as well as in 4-dimensional quadratic gravity are shown in the last chapter. 1
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Exact spacetimes in modified theories of gravity
Karamazov, Michal ; Švarc, Robert (advisor) ; Podolský, Jiří (referee)
In the review part of the thesis we summarize various modified theories of gravity, especially those that are characterized by additional curvature invariants in the Lagrangian density. Further, we review non-twisting geometries, especially their Kundt subclass. Finally, from the principle of least action we derive field equations for the case with the Lagrangian density corresponding to an arbitrary function of the curvature invariants. In the original part of the thesis we explicitly express particular components of the field equations for non-gyratonic Kundt geometry in generic quadratic gravity in arbitrary dimension. Then we discuss how this, in general fourth order, field equations restrict the Kundt metric in selected geome- trically privileged situations. We also analyse the special case of Gauss-Bonnet theory. 1
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