Through a comprehensive analysis of literary and documentary material from 1270–1500, this study offers insights into the history and significance of the late medieval string instrument known as the gittern in Western Europe. Source criticism and hermeneutics form the basis of the critical reading of the nearly hundred sources. Through these, a more refined history of the instrument is suggested, focusing on social, symbolic and musical change throughout the period. The gittern is shown to have been an instrument predominately used in noble and royal milieus for half a century before being more widely played among all ranks of society. When its popularity faded in the 15th century, it became a symbol of nostalgia. The sound and playing techniques of the gittern were well suited for the music of the late 14th century, and the decline in use was simultaneous to the developments of new genres and compositional techniques where other sounds were sought.

Die ultrakalte Atom- und Molekülephysik, zu welcher man zum Beispiel bei der Bose-Einstein-Kondensation von verdünnten Gasen Zugang hat, wurde untersucht. In solchen Systemen dominieren Zwei-Körper-Stöße und ihre detaillierte Untersuchung ist eines der zentralen Themen dieser Arbeit. Diese wurden durchgeführt unter Berücksichtigung von elementaren chemischen Reaktionen, Photoassoziation und magnetischen Feshbach-Resonanzen. Weiterhin wurden Untersuchungen von Atomen in optischen Gittern durchgeführt. Die Viel-Teilchen-Systeme wurden nicht nur mit dem üblichen mean-field Ansatz behandelt, sondern auch darüber hinausgehend, um die voll korrelierte Bewegung zu simulieren. / The ultracold atomic and molecular physics as it is accessible, e.g., in Bose-Einstein condensates of dilute gases was investigated. In such systems two-body collisions are dominant and their detailed study is one of the central topics of this work. They were done considering elementary chemical reactions as photoassociation, and magnetic Feshbach resonances. Additionally, studies of atoms in optical lattice sites were carried out. The many-body systems were not only considered within the usually adopted mean-field approach but also beyond that in order to simulate the fully correlated motion.