Analysis of the pion-kaon sigma-term and related topics

We calculate the one-loop contributions to the difference \Delta_{\pi K} between the isoscalar on-shell pion-kaon scattering amplitude at the Cheng-Dashen point and the scalar form factor \Gamma_K (2M_\pi^2) in the framework of three flavor chiral perturbation theory. These corrections turn out to be small. This is further sharpened by treating the kaons as heavy fields (two flavor chiral perturbation theory). We also analyze the two-loop corrections to the kaon scalar form factor based on a dispersive technique. We find that these corrections are smaller than in the comparable case of the scalar form factor of the pion. This is related to the weaker final state interactions in the pion-kaon channel.Comment: 25 pp, 3 fig

Non-commensurate epitaxy of organic layers

The field of organic electronics is flourishing amidst applications in the entertainment and energy sectors which are based on stacks of different organic materials. Each layer or interface between layers serves a special purpose, such as injection, extraction, transport, and blocking of charge carriers. While in industrial applications polycrystalline films are often more cost-effective, it is films with a high degree of long-range order that excel in performance since low molecular order and grain boundaries reduce the charge carrier mobility. Therefore, it is important to characterize and understand the ordered growth, i.e., the epitaxy, of molecular layers. The reproducible orientation of an ordered molecular layer on a crystalline substrate can often be understood within the framework of lattice epitaxy, where the adsorbate and the substrate share common sets of lattice planes. This includes subtler types of epitaxy than simply commensurate, i.e., identical lattices. This work aims to improve the experimental determination and characterization of epitaxy types in these non-commensurate cases, using low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM), as well as the understanding of the mechanisms driving the epitaxy. It is discussed which implications for LEED arise from structural modulations in non-commensurate epitaxial layers. For this, a theoretical treatment in the form of a simplified structure factor allows for a quite intuitive and helpful insight into an otherwise complicated diffraction theory of modulated structures. This allows for the verification and explanation of the incommensurate epitaxy of hexa-peri-hexabenzocoronene adsorbed on graphite. Comparing first-principles-based calculations with experimental results, it is unequivocally shown that the system represents an example of orientational epitaxy. Moreover, the findings constitute the first direct prove of static lattice distortions leading to this type of epitaxy

MSO Queries on Trees: Enumerating Answers under Updates Using Forest Algebras

We describe a framework for maintaining forest algebra representations that are of logarithmic height for unranked trees. Such a representations can be computed in O(n) time and updated in O(log(n)) time. The framework is of potential interest for data structures and algorithms for trees whose complexity depend on the depth of the tree (representation). We provide an exemplary application of the framework to the problem of efficiently enumerating answers to MSO-definable queries over trees which are subject to local updates. We exhibit an algorithm that uses an O(n) preprocessing phase and enumerates answers with O(log(n)) delay between them. When the tree is updated, the algorithm can avoid repeating expensive preprocessing and restart the enumeration phase within O(log(n)) time. Our algorithms and complexity results in the paper are presented in terms of node-selecting tree automata representing the MSO queries

Power counting in baryon chiral perturbation theory including vector mesons

It is demonstrated that using a suitable renormalization condition one obtains a consistent power counting in manifestly Lorentz-invariant baryon chiral perturbation theory including vector mesons as explicit degrees of freedom.Comment: 8 pages, REVTeX 4, 3 figure

Case study: Near real-time thermal mapping to support firefighting and crisis management

Hot and dry summers have led to an increase in forest fires both concerning num-bers and intensity in north-eastern Germany in the last years. In the project FireSense the German Aerospace Center (DLR) has adapted its sensor system MACS (Modular Airborne Camera System) with a set of thermal mid- and long wave infrared (MWIR and LWIR) cam-eras to detect, monitor and quantify high temperature events (HTE) like forest fires. Ground-based, airborne and spaceborne measurements over fire-experiments are synchronized for cross-validation of the systems and to test the developed workflows. In summer 2019 gas flaring tests were conducted in cooperation of DLR and the Federal In-stitute for Material Research and Testing (BAM), parallel several large forest fires in Bran-denburg (Lieberose) and Mecklenburg-Vorpommern (Lübtheen) developed. In coordination with the crisis management group (local authorities, firefighters, armed forces, federal po-lice) to get the permits MACS conducted 3 flights over the fires in altitudes between 6000 (sunny) down to 3500 ft (under clouds), Lübtheen was covered twice, on July 2 and July 4, when the fire was already under control. Synchronously firefighting helicopters operated close to ground, also delivering videos of the fires for visual interpretation. To get both background temperatures for orientation and landscape features and also infor-mation about the fires within one data set, a broad calibration range for the LWIR camera was commanded. Using synchronized position- and orientation data of MACS with given calibration data and a Digital Terrain Model, direct geocoding and the processing of near real-time mosaics was possible using the DLR workflow even without post-processing. The accuracy was sufficient for planning purposes. Geo-tiff maps were delivered shortly after landing within less than three hours. The real-time capabilities of the system could not be used as the flights were conducted on very short notice and the radio link was not installed. The thermal data were delivered as false color heat maps. They show the thermal anomalies very well, clearly discriminating burning area, recently burnt area and unaffected forest. In the RGB data the ground fires are rarely visible as they are covered by and almost did not affect the closely standing crowns. The spread of the fires can be seen in the overlapping re-gions of adjacent flight lines. Data exchange and use of the data proved to be difficult due to limited data rates and IT in-frastructure in the command and situation center in the field, sometimes taking more time than the acquisition and processing. This reduces the practical benefit for the data in the field. For future planned experiments for real-time mapping of forest fires this will be one of the main points to improve the latency of the data transfer to the control center ideally by us-ing a live data link and to optimize the coordination with the control center. Further activi-ties will be coordinated by the Helmholtz Innovation Lab OPTSAL (Optische Technologien für Situationserfassung im Sicherheitsbereich), which was started at DLR in 2020. In OPTSAL hard- and software solutions are developed and activities concerning situational awareness for safety and security are coordinated with industry and authorities

ZUMAL: Zielgruppenspezifische Gesprächsauswahl aus Korpora gesprochener Sprache

ZuMal ist ein im Rahmen des Projekts ZuMult entwickeltes Werkzeug, welches eine Vorauswahl an Sprechereignissen aus den beiden Korpora FOLK und GeWiss nach sprachdidaktisch relevanten und schwierigkeitsbezogenen Kriterien ermöglicht. Hierfür werden zum einen Kriterien genutzt, die auf die Metadaten der Sprechereignisse zurückgehen (so etwa die Art des Gesprächs, bspw. Telefongespräch, Gespräch beim Arbeitsamt, Tischgespräch; die Gesprächsthemen, die Sprachregion und die Dauer). Zum anderen wird auf Informationen zurückgegriffen, die automatisiert aus den Daten gewonnen werden können und aus der Perspektive der Vermittlung des Deutschen als Fremd- und Zweitsprache mit besonderen Herausforderungen für Lerner:innen mit Deutsch als L2 assoziiert werden. Dazu gehören u.a. der Wortschatz und dessen Zugehörigkeit zu den Niveaustufen des gemeinsamen Europäischen Referenzrahmens, die Standardnähe/-ferne, die Sprechgeschwindigkeit, die Anzahl an Überlappungen verschiedener Sprecher:innen sowie das Vorkommen ausgewählter Mündlichkeitsphänomene und Wortarten. Im Beitrag sollen die in ZuMal bereitgestellten Auswahlparameter näher beschrieben werden. Im Fokus stehen dabei insbesondere die sprachdidaktischen Konzepte, die den mit Schwierigkeit assoziierten Parametern zugrunde gelegt wurden. Anhand exemplarischer Auswertungen wird zudem gezeigt, welche Ausprägungen die aktuell in FOLK und GeWiss enthaltenen Daten im Hinblick auf die Auswahlparameter zeigen

Vorstellung eines photogrammetrischen Kamerasystems für UAV‘s mit hochgenauer GNSS/INS Information für standardisierte Verarbeitungsverfahren

Es werden die ersten Ergebnisse eines metrischen Luftbildkamerasystems für unbemannte Fluggeräte unter 5kg Abflugmasse vorgestellt. Der aktuelle Prototyp basiert auf dem vom DLR entwickelten „Modular Airborne Camera System“ (MACS) und dient als Flugmuster für die Verifizierung des Konzepts unter realen Einsatzbedingungen. Dazu wurde das Ka-merasystem geometrisch kalibriert und ein erster Bildmessflug photogrammetrisch ausge-wertet. Die Bewertung erfolgt anhand der Aerotriangulation aller Luftbildaufnahmen unter Verwendung von 32 Kontrollpunkten

Absolute frequency measurement of the magnesium intercombination transition 1S0→3P1^1S_0 \to ^3P_1

We report on a frequency measurement of the $(3s^2)^1S_0\to(3s3p)^3P_1$ clock transition of $^{24}$Mg on a thermal atomic beam. The intercombination transition has been referenced to a portable primary Cs frequency standard with the help of a femtosecond fiber laser frequency comb. The achieved uncertainty is $2.5\times10^{-12}$ which corresponds to an increase in accuracy of six orders of magnitude compared to previous results. The measured frequency value permits the calculation of several other optical transitions from $^1S_0$ to the $^3P_J$-level system for $^{24}$Mg, $^{25}$Mg and $^{26}$Mg. We describe in detail the components of our optical frequency standard like the stabilized spectroscopy laser, the atomic beam apparatus used for Ramsey-Bord\'e interferometry and the frequency comb generator and discuss the uncertainty contributions to our measurement including the first and second order Doppler effect. An upper limit of $3\times10^{-13}$ in one second for the short term instability of our optical frequency standard was determined by comparison with a GPS disciplined quartz oscillator.Comment: 8 pages, 8 figure

Are all Boer-Mulders functions alike?

Chirally odd generalized parton distributions (GPDs) and the Boer-Mulders function provide valuable information about spin-orbit correlations for quarks in nucleons and other hadrons. We compare results for the relevant GPD $\bar{E}^q_T$ from a variety of phenomenological models as well as recent lattice results. We find that $\bar{E}^q_T>0$ for nucleons as well as the pion and for both $u$ and $d$ quark. As a result, the corresponding Boer Mulders functions are all expected to be negative. The sign of $\bar{E}^q_T$ arises from the relative sign between the upper and lower Dirac components for the quark wave functions.Comment: 8 pages, 1 figur

S-wave Kpi scattering in chiral perturbation theory with resonances

We present a detailed analysis of S-wave Kpi scattering up to 2 GeV, making use of the resonance chiral Lagrangian predictions together with a suitable unitarisation method. Our approach incorporates known theoretical constraints at low and high energies. The present experimental status, with partly conflicting data from different experiments, is discussed. Our analysis allows to resolve some experimental ambiguities, but better data are needed in order to determine the cross-section in the higher-energy range. Our best fits are used to determine the masses and widths of the relevant scalar resonances in this energy region.Comment: 40 pages, 6 figure