Leopold Mathelitsch

Physics of defects in nematic liquid crystals

Liquid-crystal phases are typical examples of soft and complex materials that exhibit an abundance of different phenomena. In this paper we present some of our results contributing to the understanding of the physics of defects in nematic liquid crystals. The examples presented exhibit many features that are also of interest for other branches of physics. We describe nematic point defects, the annihilation dynamics of a defect and anti-defect pair, and the coarsening dynamics of a dense pattern of defects after a sudden symmetry-breaking phase transition.

Lectures on quark matter

Quark Matter Production in Heavy-Ion Collisions.- Theory of High-Energy A+A at RHIC.- Dense Quark Matter in Compact Stars.- Theory of the Quark-Gluon Plasma.- Thermal Gauge Field Theories.- Lattice QCD at High Temperature and Density.- Nonperturbative Phenomena and Phases of QCD.- The Color Glass Condensate and Small-x Physics.

Relativistic parametrization of separable potentials for πN channels

Abstract We present for all S- and P-waves of the πN interactions a separable potential parametrization within the framework of the Blankenbecler-Sugar formalism. In the P 11 case we are able to reproduce the sign change of the phase and the pole in a correct way.

Report and recommendations on multimedia materials for teaching and learning electricity and magnetism

This paper presents the results of a peer review of multimedia materials for teaching and learning electricity and magnetism prepared as a part of the annual activities undertaken by an international group of scientists associated with Multimedia Physics in Teaching and Learning. The work promotes the use of valuable and freely accessible information technology materials for different levels of teaching, mostly higher education. The authors discuss the process of selecting resources and the rubrics used in the rating process. The reviews of high-quality learning resources are presented along with descriptions of valuable didactical features.

Electromagnetic form factors from polarization experiments

Abstract The determination of the electromagnetic form factors from polarization measurements in elastic electron scattering off nuclei of spin s is outlined. After establishing the relationship between the products of amplitudes and the experimental observables in the “magic” optimal frame (which is the most suitable for one-particle-exchange processes), the amplitudes in that frame are related to the more traditional multipole form factors, and an experimental program is outlined for the determination of the amplitudes and, thereby, the form factors. The results complement and illuminate results obtained previously in more conventional formalisms in more elaborate ways. In particular, it is shown that by using the magic frame all elastic form factors can be determined at a given energy and angle without polarized electrons in any of the experiments.

Nucleon-deuteron low energy parameters

Abstract Momentum space Faddeev equations are solved for nucleon-deutron scattering and effective range parameters are calculated. A reverse trend is found in the two spin states by 4 a nd 4 a pd and 2 a pd 2 a nd which is in agreement with a configuration space calculation, but in conflict with all existing experiments. The Coulomb contributions to the effective range are small in quartet but sizeable in doublet scattering.

Correlations between potentials and observables in the nn interaction

Abstract We study the effects of the components of the soft-core and velocity-dependent Paris nucleon-nucleon potential on the scattering observables for laboratory energies, T L , between 10 and 350 MeV. Knowledge of these correlations is useful to indicate constraints on components of the nucleon-nucleon force. The velocity-dependent component, attractive at low energy and repulsive at high energy, plays a role at all energies. The polarisation P , the depolarisation D and the parameters D t , A , R , C KP and C NN are good tests for the tensor, spin-orbit and, to a smaller extent, quadratic spin-orbit forces. The isovector tensor force contribution is important at low energy and that of the isovector spin-orbit at high energy. The isoscalar tensor force effect is large at all energies and that of the isoscalar spin-orbit force rather small. The potential without quadratic spin-orbit term reproduces well the experimental data for T L

Narrow three-meson resonances☆

Abstract A three-body isobar model of type proposed by Aaron, Amado and Young is applied to the πππ-and ππη-systems in the channels with the quantum numbers of the ω- and η′-resonances, respectively. Using as two-body input separable potentials, which reproduce the wide resonances of the ππ-and πη-subsystems, the model predicts in a natural way the masses and, moreover, the very narrow widths of the ω- and η′-mesons. There are indications that our finding of a relation between the mass and the width of a resonance works also for resonances with higher mass. Our results also imply that the conjectured stable πNN bound state with isospin 2 does not exist.

Several versions of the bonn N-N potential tested in elastic e-d scattering

Abstract We present results for the electromagnetic form factors and the tensor polarization of elastic e-d scattering calculated with the new Bonn N-N potential. In particular, we consider the three versions Full Bonn, OBEPQ, and OBEPR and compare their predictions to experimental data at momentum transfers q 2 ≲ 80 fm −2 . In our calculations we have taken into account the effects of explicit energy dependence of the N-N interaction (in case of the Full Bonn potential), of meson-exchange currents, and of relativistic corrections.

Deuteron form factors and e-d polarization observables for the Paris and Graz-II potentials

SummaryElastic e-d scattering is studied by using the meson-theoretical Paris potential and the nonlocal separable Graz-II potential. Electric and magnetic form factors are calculated with inclusion of meson exchange currents and compared to existing experimental data. Deuteron vector and tensor polarizations and predicted and discussed in relation to the deuteron wave functions of the potential models considered. Thereby the off-shell behaviour of the Graz-II interaction is found to be close to the one of the Paris potential over the most important domain of low and moderate off-shell momenta.RiassuntoSi studia lo scattering elastico e-d utilizzando il potenziale dei mesoni teorici di Parigi e il potenziale non locale separabile di Graz II. Si calcolano fattori di forma elettrici e magnetici con l’inclusione di correnti di scambio di mesoni e si confrontano con i dati sperimentali esistenti. Si prevedono, le polarizzazioni vettoriali e tensoriali del deuterone e le si discute in relazione alle funzioni d’onda del deuterone dei modelli di potenziale considerati. Si trova perciò che il comportamento al di fuori dello strato dell’interazione di Graz II è simile a quello del potenziale di Parigi nel dominio piú importante degli impulsi bassi e moderati al di fuori dello strato.РезюмеИсследуется упругое e-d рассеяние, исполязуя мезонный теоретический потенциал Парижа и нелокальный разделяемый потенциал Граца—II. Вычисляются электрический и магнитный форм-факторы с включением мезонных обменных токов. Проводится сравнение с имеющимися экспериментальными данными. Предсказываются векторная и тензорная поляризации дейтронов. Предсказания обсуждаются в связи с волновыми функциями дейтронов для рассмотренных моделей потенциалов. Получено, что внеоболочечное поведение взаимодействия Граца—II является близким к поведению потенциала Парижа во всей наиболее важной области малых и промежуточных внеоболочечных импульсов.