Classical and quantum cosmology of Born-Infeld type models

We discuss Born-Infeld type fields (tachyon fields) in classical and quantum cosmology. We first partly review and partly extend the discussion of the classical solutions and focus in particular on the occurrence of singularities. For quantization, we employ geometrodynamics. In the case of constant potential, we discuss both Wheeler-DeWitt quantization and reduced quantization. We are able to give various solutions and discuss their asymptotics. For the case of general potential, we transform the Wheeler-DeWitt equation to a form where it leads to a difference equation. Such a difference equation was previously found in the quantization of black holes. We give explicit results for the cases of constant potential and inverse squared potential and point out special features possessed by solutions of the difference equation.Comment: 14 pages, 8 figures, published versio

Infrared Spectroscopic Analysis of the Inorganic Deposits from Water in Domestic and Technical Heat Exchangers

Peer reviewedPublisher PD

Origin of the inflationary Universe

We give a consistent description of how the inflationary Universe emerges in quantum cosmology. This involves two steps: Firstly, it is shown that a sensible probability peak can be obtained from the cosmological wave function. This is achieved by going beyond the tree level of the semiclassical expansion. Secondly, due to decoherence interference terms between different semiclassical branches are negligibly small. The results give constraints on the particle content of a unified theory.Comment: LATEX, 6 pages, selected for honorable mention in the 1999 Essay Competition of the Gravity Research Foundation. To appear in Mod. Phys. Lett.

A modified Ehlers model for the description of inelastic behavior of porous structures

This paper describes a modification of Ehlers' model for the inelastic behavior of granular media. The modified model can be applied for describing the inelastic behavior of porous media. The key feature is a subtle change of the yield potential, which allows the correct orientation of the triangular-shaped yield surface cross sections depending on the hydrostatic stress state. The model is incorporated into a general framework for isotropic plasticity. An elastic predictor/corrector algorithm is employed to solve the constitutive equations. The necessary derivatives for a Newton update are also given in detail. The model is calibrated using stress, and strain data obtained from finite element simulations of a generic highly porous open-cell Wheire-Phelan foam

Effective action and decoherence by fermions in quantum cosmology

We develop the formalism for the one-loop no-boundary state in a cosmological model with fermions. We use it to calculate the reduced density matrix for an inflaton field by tracing out the fermionic degrees of freedom, yielding both the fermionic effective action and the standard decoherence factor. We show that dimensional regularisation of ultraviolet divergences would lead to an inconsistent density matrix. Suppression of these divergences to zero is instead performed through a nonlocal Bogoliubov transformation of the fermionic variables, which leads to a consistent density matrix. The resulting degree of decoherence is less than in the case of bosonic fields.Comment: Latex, 26 page

Synergy of human spine in neutral posture

Musculoskeletal disorders -- Functional anatomy of the trunk -- Compendium of articles -- Hybrid kinematic method -- Effect of the geometry and load configuration -- Effect of muscles -- Pelvic rotation and muscles

Totalsynthese und biologische Evaluierung von Cyclomarin-Derivaten

In den späten 1990er Jahren berichtete zum ersten Mal die Gruppe um Clardy über die Isolierung und Strukturaufklärung einer kleinen Familie von peptischen Naturstoffen aus dem marinen Streptomyceten-Stamm CNB-982, den sogenannten Cyclomarine A-C. Diese weisen ein höchst ausgefallenes Wirkspektrum auf. So wirken sie einerseits antibiotisch, vor allem gegen resistente Mycobakterien und andererseits gegen Plasmodium falciparum, den Erreger von Malaria. Diese Doktorarbeit beschreibt die Synthese neuer Cyclomarin-Analoga, mit denen durch Struktur-Aktivitäts-Beziehungen ein tieferer Einblick in Bezug auf die biologischen Aktivitäten gegenüber Mycobacterium tuberculosis und Plasmodium falciparum ermöglicht wurde. In diesem Zusammenhang wurden bereits 16 der 21 synthetisierten Derivate auf ihre Wirkung untersucht. Durch schrittweise Variation und Vereinfachung der nicht-proteinogenen Amino-säuren des Cyclomarin-Grundgerüstes gelang es so, zwei unterschiedliche potentielle Leit-strukturen für beide Targets abzuleiten