Dynamics and Motional Coherence of Fermions Immersed in a Bose Gas

Die vorliegende Arbeit untersucht den Einfluss eines Bosegases aus Natriumatomen auf die Kohärenz fermionischer Lithiumatome, die sich in einer Superposition zweier Bewegungszustände befinden. Zu diesem Zweck implementieren und charakterisieren wir ein Lithium-selektives Gitterpotential. Das Verschieben der Gitterposition koppelt Zustände aus Blochbändern unterschiedlicher Parität und führt bei periodischer Modulation zu Rabi-Oszillationen zwischen dem ersten und zweiten Blochband. Mit Hilfe dieses Kopplungsmechanismus untersuchen wir die zeitliche Entwicklung der Lithiumatome in Ramsey- und Spin-Echo-Experimenten. Die Wechselwirkung mit den Natriumatomen verursacht einen Kohärenzzerfall der Lithiumatome, dessen Zerfallszeit wir durch den Vergleich der Spin-Echo-Signale mit und ohne bosonischem Hintergrund bestimmen. Wir beobachten, dass der Verlust der Kohärenz auf einer etwas längeren Zeitskala als die Relaxation zwischen den Blochbändern erfolgt und schließen daraus, dass der Kohärenzzerfall durch Relaxationsprozesse getrieben ist. Zudem überprüfen wir diese Schlussfolgerung anhand einer Mastergleichung, die die zeitliche Entwicklung einzelner Teilchen in einem Bosegas beschreibt. Unsere Berechnungen stimmen qualitativ mit unseren Beobachtungen überein und bestätigen, dass die Dynamik der Lithiumatome durch Relaxationsprozesse dominiert ist

Feshbach spectroscopy and analysis of the interaction potentials of ultracold sodium

We have studied magnetic Feshbach resonances in an ultracold sample of Na prepared in the absolute hyperfine ground state. We report on the observation of three s-, eight d-, and three g-wave Feshbach resonances, including a more precise determination of two known s-wave resonances, and one s-wave resonance at a magnetic field exceeding 200mT. Using a coupled-channels calculation we have improved the sodium ground-state potentials by taking into account these new experimental data, and derived values for the scattering lengths. In addition, a description of the molecular states leading to the Feshbach resonances in terms of the asymptotic-bound-state model is presented.Comment: 11 pages, 4 figure

Feshbach spectroscopy and scattering properties of ultracold Li+Na mixtures

We have observed 26 interspecies Feshbach resonances at fields up to 2050 G in ultracold $^6$Li+$^{23}$Na mixtures for different spin-state combinations. Applying the asymptotic bound-state model to assign the resonances, we have found that most resonances have d-wave character. This analysis serves as guidance for a coupled-channel calculation, which uses modified interaction potentials to describe the positions of the Feshbach resonances well within the experimental uncertainty and to calculate their widths. The scattering length derived from the improved interaction potentials is experimentally confirmed and deviates from previously reported values in sign and magnitude. We give prospects for $^7$Li+$^{23}$Na and predict broad Feshbach resonances suitable for tuning.Comment: 8 pages, 4 figures, version as published in PR

The ambivalent shadow of the pre-Wilsonian rise of international law

The generation of American international lawyers who founded the American Society of International Law in 1906 and nurtured the soil for what has been retrospectively called a “moralistic legalistic approach to international relations” remains little studied. A survey of the rise of international legal literature in the U.S. from the mid-19th century to the eve of the Great War serves as a backdrop to the examination of the boosting effect on international law of the Spanish American War in 1898. An examination of the Insular Cases before the US Supreme Court is then accompanied by the analysis of a number of influential factors behind the pre-war rise of international law in the U.S. The work concludes with an examination of the rise of natural law doctrines in international law during the interwar period and the critiques addressed.by the realist founders of the field of “international relations” to the “moralistic legalistic approach to international relation

The United Nations Security Council and the enforcement of international humanitarian law

This Article discusses the competences and powers of the UN Security Council in securing compliance with international humanitarian law, in particular through the adoption of the measures provided in Chapter VII of the Charter: The competence of the Council in this field can be founded on several legal grounds: on a broad interpretation of the notion of “threat to the peace” (Article 39 of the Charter), on Article 94(2) with regard to the International Court of Justice's judgments establishing violations of the jus in bello and also on the customary duty to ensure respect for international humanitarian law as reflected in Article 1 Common to the 1949 Geneva Conventions on the Protection of the Victims of War. In particular, such customary provision empowers the Security Council to react to any violation of international humanitarian law regardless of a nexus with concerns of international stability. Although the Council has adopted a variety of measures in relation to violations of the laws of war, the most incisive ones are those provided in Articles 41 and 42 of Chapter VII, which however are not without problems. The role the Security Council has played in the enforcement of international humanitarian law has been criticized because of its selective and opportunistic approach, which is due to the political nature of the organ. Also, in several instances the Council, far from securing compliance with the jus in bello, has instead interfered with its application. However selective and imperfect the Council's approach might be, though, its power to adopt decisions binding on UN members and its competence to take or authorize coercive measures involving the use of force make it potentially a formidable instrument against serious violations of international humanitarian law, partly remedying the lack of enforcing mechanisms in the treaties on the laws of war

Construire des pratiques participatives dans les bibliothèques

Participer et faire participer les citoyens, les publics ? Qui participe, comment et jusqu’où ? Que devient le professionnel avec ce nouveau paradigme ? Comment emporter l’adhésion des habitants ? De plus en plus de bibliothèques s’engagent activement dans la participation, selon des modalités et des niveaux d’implication variés. Cette mutation des pratiques renouvelle les réflexions engagées autour des publics : ne plus seulement mettre les publics au centre du cercle mais créer les conditions pour les accompagner à dessiner ce cercle. Empowerment, co-construction, crowdsourcing, savoirs partagés, participation démocratique… cet ouvrage permet de clarifier les notions attachées aux dynamiques participatives et propose un cadre de réflexion qui permettra aux bibliothécaires de construire leurs modes d’action entre PirateBox, BiblioRemix, comités d’usagers, design de service et autres formes de projets participatifs. Organisé en trois parties - Repenser la bibliothèque ensemble, Partager les savoirs, Décider ensemble ? – ce volume présente également un ensemble de témoignages de praticiens du sujet, en France et aux États-Unis, de la préfiguration d’une bibliothèque à son réaménagement, en passant par la création de plateformes collaboratives et de nouveaux services. L’expérience d’un musée et l’aventure d’un centre social viennent enrichir le panorama