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In the theory of false vacuum eternal inflation the false vacuum decays whenever the inflaton potential has multiple minima. The decay means a nucleation of a bubble with a different density in vacuum energy. Inflation may occur within the bubble eventually giving way to the hot big bang with a subsequent evolution that is consistent with current observations. Interest in this picture has recovered as it became generally accepted that a compactification of the extra dimensions in string theory leads to an effective potential with a vast number of minima, the landscape of string theory. In the first part of this thesis the effects that can be expected if the surrounding of the bubble is dynamical are elucidated. In particular, it is shown how the bubble evolves in the presence of a fluid in the background, and moreover, the effects of a radial inhomogeneity in energy density and spatial curvature. Second, collisions of bubbles would disturb the homogeneity and isotropy of their interior, which, in turn, could lead to observable effects in the cosmic microwave background radiation. It will be clarified whether Minkowski functionals are a promising tool to detect such signals.

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Dr. rer. nat.: Born on June 27th 1981 in Gießen, Germany. Studies of Physics at the Institute for Theoretical Physics and Astrophysics, Würzburg University, Germany. Employed at the Free State of Bavaria as a student teacher for Mathematics and Physics.

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