On the role of complex phases in the quantum statistics of weak measurements

Weak measurements carried out between quantum state preparation and post-selection result in complex values for self-adjoint operators, corresponding to complex conditional probabilities for the projections on specific eigenstates. In this paper it is shown that the complex phases of these weak conditional probabilities describe the dynamic response of the system to unitary transformations. Quantum mechanics thus unifies the statistical overlap of different states with the dynamical structure of transformations between these states. Specifically, it is possible to identify the phase of weak conditional probabilities directly with the action of a unitary transform that maximizes the overlap of initial and final states. This action provides a quantitative measure of how much quantum correlations can diverge from the deterministic relations between physical properties expected from classical physics or hidden variable theories. In terms of quantum information, the phases of weak conditional probabilities thus represent the logical tension between sets of three quantum states that is at the heart of quantum paradoxes

Zur Erinnerung an Gustav Robert Kirchhoff / Aufsätze von Robert v Helmholtz, August W. v. Hofmann, Friedrich Pockels und Emil Warburg zusammengestellt von Gabriele Dörflinger

Gustav Robert Kirchhoff (1824-1887) lehrte von 1854 bis 1875 als Physikprofessor an der Heidelberger Universität. Hier entdeckte er 1859/60 gemeinsam mit Robert Wilhelm Bunsen die Spektralanalyse. Die Aufsatzsammlung enthält: 1.) Robert von Helmholtz: Gustav Robert Kirchhoff 2.) August W. Hofmann: Gedächtnisrede auf Gustav Robert Kirchhoff 3.) Friedrich Pockels: Gustav Robert Kirchhoff 4.) Emil Warburg: Zur Erinnerung an Gustav Robert Kirchhof

Die Etablierung von E-Learning-Szenarien an Gymnasien – ein Pilotprojekt in Sachsen und seine Erkenntnisse

Webbasierte Lehr-Lernformen sind Gegenstand zahlreicher Forschungsprojekte, die häufig auf den technischen Hintergrund und den didaktischen Einsatz im Kontext der Ausbildung an Universitäten und Hochschulen fokussieren. In den Schulen befindet sich der Einsatz von E-Learning im Unterricht vorwiegend im Erprobungsstatus, da didaktische Szenarien, die Lehrer zu einem sinnvollen, lernzielorientierten Einsatz dieser Lehr-Lernmethode im Schulunterricht befähigen, erst noch zu entwickeln sind. Mit dem Übergang von der Schule zur Hochschule treffen die Abiturienten als Studienanfänger auf eine Hochschullandschaft, in der Lernumgebungen weitgehend etabliert sind. Selbstbestimmtes webbasiertes Lernen, das Organisieren des eigenen Studienablaufes via Webportal aber auch die im Vergleich zum Schulunterricht veränderte Methodik der Inhaltsvermittlung in den gewählten Studienfächern bedeuten für die jungen Studentinnen und Studenten neue Herausforderungen, denen sie teilweise unzureichend vorbereitet gegenüber stehen. Aus dem ESF-geförderten Projekt „Übergang Schule-Hochschule mit Unterstützung internetbasierter E-Learning-Tools (UnIbELT)“ sind Erfahrungen hervorgegangen, wie die Etablierung geeigneter, didaktisch aufbereiteter E-Learning-Szenarien in den Schulen einen Beitrag dazu leisten kann, künftige Studierende auf den Übergang zur Hochschule vorzubereiten und sie mit den Studienanforderungen vertraut zu machen. Diese Erfahrungen stützen sich auf mehr als 70 durchgeführte E-Learning-Kurse in 21 Gymnasien Sachsens, an denen seit 2009 mehr als 1100 Schüler der Sekundarstufe II teilgenommen haben

Bulk Band Structure of Bi2_2Te3_3

The bulk band structure of Bi$_2$Te$_3$ has been determined by angle-resolved photoemission spectroscopy and compared to first-principles calculations. We have performed calculations using the local density approximation (LDA) of density functional theory and the one-shot $GW$ approximation within the all-electron full-potential linearized augmented-plane-wave (FLAPW) formalism, fully taking into account spin-orbit coupling. Quasiparticle effects produce significant changes in the band structure of \bite~when compared to LDA. Experimental and calculated results are compared in the spectral regions where distinct differences between the LDA and $GW$ results are present. Overall a superior agreement with $GW$ is found, highlighting the importance of many-body effects in the band structure of this family of topological insulators.Comment: 8 pages, 5 Figure

Evidence for a direct band gap in the topological insulator Bi2Se3 from theory and experiment

Using angle-resolved photoelectron spectroscopy and ab-initio GW calculations, we unambiguously show that the widely investigated three-dimensional topological insulator Bi2Se3 has a direct band gap at the Gamma point. Experimentally, this is shown by a three-dimensional band mapping in large fractions of the Brillouin zone. Theoretically, we demonstrate that the valence band maximum is located at the Brillouin center only if many-body effects are included in the calculation. Otherwise, it is found in a high-symmetry mirror plane away from the zone center.Comment: 8 pages, 4 figure

Baseline MELD score predicts hepatic decompensation during antiviral therapy in patients with chronic hepatitis C and advanced cirrhosis

Background and Aims: In patients with advanced liver cirrhosis due to chronic hepatitis C virus (HCV) infection antiviral therapy with peginterferon and ribavirin is feasible in selected cases only due to potentially life-threatening side effects. However, predictive factors associated with hepatic decompensation during antiviral therapy are poorly defined. Methods: In a retrospective cohort study, 68 patients with HCV-associated liver cirrhosis (mean MELD score 9.18±2.72) were treated with peginterferon and ribavirin. Clinical events indicating hepatic decompensation (onset of ascites, hepatic encephalopathy, upper gastrointestinal bleeding, hospitalization) as well as laboratory data were recorded at baseline and during a follow up period of 72 weeks after initiation of antiviral therapy. To monitor long term sequelae of end stage liver disease an extended follow up for HCC development, transplantation and death was applied (240weeks, ±SD 136weeks). Results: Eighteen patients (26.5%) achieved a sustained virologic response. During the observational period a hepatic decompensation was observed in 36.8%. Patients with hepatic decompensation had higher MELD scores (10.84 vs. 8.23, p14, respectively. Baseline MELD score was significantly associated with the risk for transplantation/death (p<0.001). Conclusions: Our data suggest that the baseline MELD score predicts the risk of hepatic decompensation during antiviral therapy and thus contributes to decision making when antiviral therapy is discussed in HCV patients with advanced liver cirrhosis