Analytic continuation and numerical evaluation of the kite integral and the equal mass sunrise integral

We study the analytic continuation of Feynman integrals from the kite family, expressed in terms of elliptic generalisations of (multiple) polylogarithms. Expressed in this way, the Feynman integrals are functions of two periods of an elliptic curve. We show that all what is required is just the analytic continuation of these two periods. We present an explicit formula for the two periods for all values of $t \in {\mathbb R}$. Furthermore, the nome $q$ of the elliptic curve satisfies over the complete range in $t$ the inequality $|q|\le 1$, where $|q|=1$ is attained only at the singular points $t\in\{m^2,9m^2,\infty\}$. This ensures the convergence of the $q$-series expansion of the $\mathrm{ELi}$-functions and provides a fast and efficient evaluation of these Feynman integrals.Comment: 30 pages, version to be publishe

Modelling land-use and land-cover change and related environmental impacts in Northern Mongolia

In der Nordmongolei haben in den letzten Jahrzehnten signifikante Landnutzungs- und Landbedeckungsänderungen stattgefunden, welche sich zunehmend negativ auf die Ökosysteme und deren Funktionen auswirken. In Verbindung mit Klimawandel, abnehmender Wasserverfügbarkeit und zunehmender Wassernutzung, bedarf es integrierter Ansätze, um Auswirkungen auf Mensch und Umwelt abschätzen zu können. Ziel dieser Dissertation war die Entwicklung und Anwendung eines Simulationsmodells, welches historische, aktuelle sowie zukünftige Veränderungen der Landnutzung und Landbedeckung abbildet. Anhand von drei Fallstudien (Intensivierung im Agrarsektor, Auswirkungen von Wald- und Steppenbränden, Umweltszenarien) werden wichtige Aspekte des Landnutzungswandels bezüglich ihrer Auswirkungen analysiert und diskutiert. Die vorliegende Arbeit leistet einen wichtigen Beitrag für die Ausarbeitung von Maßnahmen zum Zwecke eines integrierten Wasserressourcen-Managements auf Einzugsgebietsebene.von Christian Schweitze

Differential equations for Feynman integrals beyond multiple polylogarithms

Differential equations are a powerful tool to tackle Feynman integrals. In this talk we discuss recent progress, where the method of differential equations has been applied to Feynman integrals which are not expressible in terms of multiple polylogarithms.Comment: 9 pages, talk given at RADCOR 201

Magnetic Field-Induced Lattice Effects in a Quasi-2D Organic Conductor Close to the Mott Metal-Insulator Transition

We present ultra-high-resolution dilatometric studies in magnetic fields on a quasi-two-dimensional organic conductor $\kappa$-(D8-BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Br, which is located close to the Mott metal-insulator (MI) transition. The obtained thermal expansion coefficient, $\alpha(T)$, reveals two remarkable features: (i) the Mott MI transition temperature $T_{MI}$ = (13.6 $\pm$ 0.6)\,K is insensitive to fields up to 10\,T, the highest applied field; (ii) for fields along the interlayer \emph{b}-axis, a magnetic-field-induced (FI) phase transition at $T_{FI}$ = (9.5 $\pm$ 0.5)\,K is observed above a threshold field $H_c \sim$ 1 T, indicative of a spin reorientation with strong magneto-elastic coupling.Comment: 5 pages, 4 figure

Citations Driven by Social Connections? A Multi-Layer Representation of Coauthorship Networks

To what extent is the citation rate of new papers influenced by the past social relations of their authors? To answer this question, we present a data-driven analysis of nine different physics journals. Our analysis is based on a two-layer network representation constructed from two large-scale data sets, INSPIREHEP and APS. The social layer contains authors as nodes and coauthorship relations as links. This allows us to quantify the social relations of each author, prior to the publication of a new paper. The publication layer contains papers as nodes and citations between papers as links. This layer allows us to quantify scientific attention as measured by the change of the citation rate over time. We particularly study how this change depends on the social relations of their authors, prior to publication. We find that on average the maximum value of the citation rate is reached sooner for authors who either published more papers, or who had more coauthors in previous papers. We also find that for these authors the decay in the citation rate is faster, meaning that their papers are forgotten sooner

Digital 3D reconstruction of two parahissian accessory bundles in a case of Wolff-Parkinson-White syndrome

Three-dimensional reconstruction of digitized histological serial sections of the cardiac conduction system yielded two accessory pathways in a case of a 24-day-old male infant who died after a short period of illness with ECG findings of Wolff-Parkinson-White syndrome. In infants, the differential diagnosis of possible accessory pathways connecting the AV conduction system, atrial or ventricular septum includes dispersed conduction system tissue without connecting features. This is why three-dimensional reconstruction is necessary in order to refute or establish connectivity of cell groups as found in histological serial slice image