ac Stark shift and multiphoton-like resonances in low-frequency driven optical lattices

We suggest that Bose-Einstein condensates in optical lattices subjected to ac forcing with a smooth envelope may provide detailed experimental access to multiphoton-like transitions between ac-Stark-shifted Bloch bands. Such transitions correspond to resonances described theoretically by avoided quasienergy crossings. We show that the width of such anticrossings can be inferred from measurements involving asymmetric pulses. We also introduce a pulse tracking strategy for locating the particular driving amplitudes for which resonances occur. Our numerical calculations refer to a currently existing experimental set-up [Haller et al., PRL 104, 200403 (2010)].Comment: 5 pages, 6 figure

Between conscience and profit: the economic- and social-order of the „Freiburg Bonhoeffer-Circle“ and its christian argumentation

Text in GermanDie wirtschaftspolitische Konzeption der Bundesrepublik Deutschland wird seit 1948 als „Soziale Marktwirtschaft“ bezeichnet. Es beruht auf den Prinzipien des Leistungswettbewerbs, geregelt durch staatliche Ordnungen und ergänzt durch einen sozialen Ausgleich. Die „Soziale Marktwirtschaft“ geht dabei einen Mittelweg zwischen einer liberalen laissezfaire Wirtschaftsordnung und einer staatlichen Planwirtschaft. Vorliegende Arbeit untersucht zum ersten Mal im Detail ein Vorläuferdokument der Sozialen Marktwirtschaft, die „Freiburger Denkschrift“ aus dem Jahr 1943. In dieser Nachkriegsordnung, eine Auftragsarbeit der „Bekennenden Kirche“, finden sich alle Grundprinzipien der später eingeführten Sozialen Marktwirtschaft, eingebettet in ein umfangreiches christliches Reformprogramm für den Wiederaufbau Deutschlands. Die Arbeit analysiert den Hintergrund der Verfasser und die Inhalte der Denkschrift. Konkret wird gezeigt, welche Überzeugungen der christlichen Ethik sich in den wirtschaftspolitischen Forderungen der Denkschrift niedergeschlagen haben. Außerdem wird die Denkschrift in den biographischen Kontext der Verfasser und die zeitgeschichtlichen theologischen Zusammenhänge eingeordnet, denn viele Thesen des Dokuments reflektieren Diskussionsprozesse der damaligen Zeit. Zudem kann gezeigt werden, dass in die Freiburger Denkschrift sowohl protestantische wie auch römisch-katholische Elemente Eingang gefunden haben.Since 1948 the economic system of the Federal Republic of Germany is called “Social Market Economy”. It is based on the principles of competitive markets, ensured by governmental competition policy and supplemented by social insurance and public assistance. The “Social Market Economy” takes a middle road between a liberal laissez-faire economy and a a centrally planned economy. The current study examines for the first time in detail the document that preceded the “Social Market Economy,” the 1943 “Freiburg Memorandum”. In this work, commissioned by the Confessing Church of the Third Reich as a post-war system, all fundamental principles of the later “Social Market Economy” can be found embedded in a comprehensive Christian reform program for the reconstruction of Germany. This dissertation analyzes the background of the authors and the contents of the memorandum. We will show specifically which convictions of Christian ethics were incorporated into the economic-political requests of the document. In addition the memorandum will be connected to the biographical context of the authors and the theological context of their time, as many theses put forward in the document reflect discussions that were in progress at that time. Also, it can be shown that Protestant as well as Roman-Catholic elements found entrance into the “Freiburg Memorandum”.Philosophy, Practical and Systematic TheologyM. Th. (Theological Ethics

Generalized acceleration theorem for spatiotemporal Bloch waves

A representation is put forward for wave functions of quantum particles in periodic lattice potentials subjected to homogeneous time-periodic forcing, based on an expansion with respect to Bloch-like states which embody both the spatial and the temporal periodicity. It is shown that there exists a generalization of Bloch's famous acceleration theorem which grows out of this representation and captures the effect of a weak probe force applied in addition to a strong dressing force. Taken together, these elements point at a "dressing and probing" strategy for coherent wave-packet manipulation, which could be implemented in present experiments with optical lattices.Comment: 12 pages, 4 figure

Controlled wave-packet manipulation with driven optical lattices

Motivated by recent experimental progress achieved with ultracold atoms in kilohertz-driven optical lattices, we provide a theoretical discussion of mechanisms governing the response of a particle in a cosine lattice potential to strong forcing pulses with smooth envelope. Such pulses effectuate adiabatic motion of a wave packet's momentum distribution on quasienergy surfaces created by spatiotemporal Bloch waves. Deviations from adiabaticity can then deliberately be exploited for exerting coherent control and for reaching target states which may not be accessible by other means. As one particular example, we consider an analog of the \pi-pulses known from optical resonance. We also suggest adapting further techniques previously developed for controlling atomic and molecular dynamics by laser pulses to the coherent control of matter waves in shaken optical lattices.Comment: 11 pages, 10 figure