Termination of Triangular Integer Loops is Decidable

We consider the problem whether termination of affine integer loops is decidable. Since Tiwari conjectured decidability in 2004, only special cases have been solved. We complement this work by proving decidability for the case that the update matrix is triangular.Comment: Full version (with proofs) of a paper published in the Proceedings of the 31st International Conference on Computer Aided Verification (CAV '19), New York, NY, USA, Lecture Notes in Computer Science, Springer-Verlag, 201

Towards a Characterisation of Emotional Intent During Scripted Scenes Using In-ear Movement Sensors

Theatre provides a unique environment in which to obtain detailed data on social interactions in a controlled and repeatable manner.This work introduces a method for capturing and characterising the underlying emotional intent of performers in a scripted sceneusing in-ear accelerometers. Each scene is acted with different underlying emotional intentions using the theatrical technique ofActioning. The goal of the work is to uncover characteristics in the joint movement patterns that reveal information on the positive ornegative valence of these intentions. Preliminary findings over 3x12 (Covid-19 restricted) non-actor trials suggests people are moreenergetic and more in-sync when using positive versus negative intentions

Observation of the spin-orbit gap in bilayer graphene by one-dimensional ballistic transport

We report on measurements of quantized conductance in gate-defined quantum point contacts in bilayer graphene that allow the observation of subband splittings due to spin-orbit coupling. The size of this splitting can be tuned from 40 to 80 $\mu$eV by the displacement field. We assign this gate-tunable subband-splitting to a gap induced by spin-orbit coupling of Kane-Mele type, enhanced by proximity effects due to the substrate. We show that this spin-orbit coupling gives rise to a complex pattern in low perpendicular magnetic fields, increasing the Zeeman splitting in one valley and suppressing it in the other one. In addition, we observe the existence of a spin-polarized channel of 6 e$^2$/h at high in-plane magnetic field and of signatures of interaction effects at the crossings of spin-split subbands of opposite spins at finite magnetic field.Comment: 5 pages, 4 figures, Supplement 6 figure

Vicinal Surfaces and the Calogero-Sutherland Model

A miscut (vicinal) crystal surface can be regarded as an array of meandering but non-crossing steps. Interactions between the steps are shown to induce a faceting transition of the surface between a homogeneous Luttinger liquid state and a low-temperature regime consisting of local step clusters in coexistence with ideal facets. This morphological transition is governed by a hitherto neglected critical line of the well-known Calogero-Sutherland model. Its exact solution yields expressions for measurable quantities that compare favorably with recent experiments on Si surfaces.Comment: 4 pages, revtex, 2 figures (.eps

Anisotropic susceptibility of ferromagnetic ultrathin Co films on vicinal Cu

We measure the magnetic susceptibility of ultrathin Co films with an in-plane uniaxial magnetic anisotropy grown on a vicinal Cu substrate. Above the Curie temperature the influence of the magnetic anisotropy can be investigated by means of the parallel and transverse susceptibilities along the easy and hard axes. By comparison with a theoretical analysis of the susceptibilities we determine the isotropic exchange interaction and the magnetic anisotropy. These calculations are performed in the framework of a Heisenberg model by means of a many-body Green's function method, since collective magnetic excitations are very important in two-dimensional magnets.Comment: 7 pages, 3 figure

Linear and nonlinear optical properties of some organoxenon derivatives

We employ a series of state-of-the-art computational techniques to study the effect of inserting one or more Xe atoms in HC2H and HC4H, on the linear and nonlinear optical (L&NLO) properties of the resulting compounds. It has been found that the inserted Xe has a great effect on the L&NLO properties of the organoxenon derivatives. We analyze the bonding in HXeC2H, and the change of the electronic structure, which is induced by inserting Xe, in order to rationalize the observed extraordinary L&NLO properties. The derivatives, which are of interest in this work, have been synthesized in a Xe matrix. Thus the effect of the local field (LF), due to the Xe environment, on the properties of HXeC2H, has also been computed. It has been found that the LF effect on some properties is significant. The calculations have been performed by employing a hierarchy of basis sets and the techniques MP2 and CCSD(T) for taking into account correlation. For the interpretation of the results we have employed the complete active space valence bond and CASSCF/CASPT2 [email protected]

Automatically proving termination and memory safety for programs with pointer arithmetic

While automated verification of imperative programs has been studied intensively, proving termination of programs with explicit pointer arithmetic fully automatically was still an open problem. To close this gap, we introduce a novel abstract domain that can track allocated memory in detail. We use it to automatically construct a symbolic execution graph that over-approximates all possible runs of a program and that can be used to prove memory safety. This graph is then transformed into an integer transition system, whose termination can be proved by standard techniques. We implemented this approach in the automated termination prover AProVE and demonstrate its capability of analyzing C programs with pointer arithmetic that existing tools cannot handle

Förderung von Kursverständnis, Fokus, Organisation und Motivation bei internationalen Online-Studierenden in asynchronen Lernsettings

Im Rahmen eines DAAD-geförderten Pilotprojektes zur Öffnung eines Präsenz-Master-Studienganges für internationale Online-Masterstudierende wurden asynchrone digitale Lernsettings entwickelt. Insbesondere galt es, das Kursmaterial von vier Vorlesungen einheitlich in Online-Kursbausteinen als Stud.IP-Courseware umzusetzen. Mitte des Wintersemesters 2021/2022 wurde eine formative Evaluation dieser Kurse hinsichtlich der Aspekte Kursverständnis, Fokus, Organisation und Motivation durchgeführt. Es wurde untersucht, welche dieser entwickelten Bausteine nachhaltig in den laufenden Lehrbetrieb integriert werden können. Es lässt sich belegen, dass besonders Lernvideos, Quizze und Kapitelzusammenfassungen das Kursverständnis, die Organisation des Lernens und den Fokus stärken. Quizze und Kapitelzusammenfassungen wirken motivierend, während insbesondere asynchron online Studierende Erklärtexte und Material zur Exploration motivierend fanden. Der Artikel schließt mit Schlussfolgerungen für die Praxis der Digitalisierung weiterer Kurse für internationale Masterstudierende in asynchronen Lernszenarien. (DIPF/Orig.