[en] We performed a self-consistent calculation of the nuclear matter properties within the Green's function scheme. Essential is the self-energy Σ(p;epsilon) (effective single-particle potential or mass operator), which determines the properties of the system. Necessary for the calculation of the effective single-particle potential is the knowledge of the scattering matrix (T-matrix) in matter, which plays in the calculation the role of an effective two-body potential. Our calculations were performed for the 'phenomenological' hardcore potential of Hamada-Johnston, the Reid-soft-core potential and the 'realistic' Paris-Nucleon-Nucleon potential. A binding energy of -5.88 MeV per nucleon was obtained. For the Reid-soft-core potential and the Paris potential we found -11 MeV and -12.2 MeV respectively. (orig./HSI)

[en] This paper discusses possible astrophysical signals by means of which quark matter may register itself in isolated millisecond pulsars and neutron stars in low-mass x-ray binaries. Implications of absolutely stable strange quark matter for white dwarfs are pointed out in the last section

No abstract available

[en] The present thesis concentrates on the signatures of strong electron-phonon coupling in phonon properties measured by inelastic neutron scattering. The inelastic neutron scattering experiments were performed on the triple-axis spectrometers 1T and DAS PUMA at the research reactors in Saclay (France) and Munich (Germany), respectively. The work is subdivided into two separate chapters: In the first part, we report measurements of the lattice dynamical properties, i.e. phonon frequency, linewidth and intensity, of the conventional, i.e. phonon-mediated, superconductor YNi₂B₂C of the rare-earth-borocarbide family. The detailed check of theoretical predictions for these properties, which were calculated in the theory group of our institute, was one major goal of this work. We measured phonons in the normal state, i.e. T>T_c, for several high symmetry directions up to 70 meV. We were able to extract the full temperature dependence of the superconducting energy gap 2Δ(T) from our phonon scans with such accuracy that even deviations from the weak coupling BCS behaviour could be clearly observed. By measuring phonons at different wave vectors we demonstrated that phonons are sensitive to the gap anisotropy under the precondition, that different phonons get their coupling strength from different parts of the Fermi surface. In the second part, we investigated the properties of Mn-O bond-stretching phonons in the bilayer manganite La_2-2xSr_1+2xMn₂O₇. At the doping level x=0.38 this compound has an ferromagnetic groundstate and exhibits the so-called colossal magnetoresistance effect in the vicinity of the Curie temperature T_C. The atomic displacement patterns of the investigated phonons closely resemble possible Jahn-Teller distortions of the MnO₆ octahedra, which are introduced in this compound by the Jahn-Teller active Mn³⁺ ions. We observed strong renormalizations of the phonon frequencies and clear peaks of the intrinsic phonon linewidth near the order wave vector of the short-range charge and orbital order present above T_C. In an neutron powder diffraction measurement at the Hahn-Meitner Institut in Berlin, we investigated the temperature dependence of the anisotropic Debye-Waller factors of the oxygen atoms in La_0.7Sr_0.3MnO₃. According to the present point of view, the sudden increase of the Debye-Waller factors at T_C should be proportional to the strength of the colossal magnetoresistance effect. However, we found experimental values for La_0.7Sr_0.3MnO₃, which are in close vicinity or even bigger than values of compounds with a much stronger magnetoresistance effect. (orig.)

[en] In a sample of 251,000 hadronic Z⁰ decays collected with the ALEPH detector at LEP, B⁰ and B⁺ mesons are identified by their semileptonic decays including a D or D* meson. The decay length of the B meson is reconstructed using the silicon microvertex detector

[en] This article consists of three parts. In part one we review the present status of dense nuclear matter calculations, and introduce a representative collection of realistic nuclear equations of state which are derived for different assumptions about the physical behavior of dense matter (baryon population, pion condensation,.possible transition of baryon matter to quark matter). In part two we review recently performed non-rotating and rotating compact star calculations performed for these equations of state. The minimum stable rotational periods of compact stars, whose knowledge is of decisive importance for the interpretation of rapidly rotating pulsars, axe determined. For this purpose two different limits on stable rotation are studied: rotation at the general relativistic Kepler period (below which mass shedding at the star's equator sets in), and, secondly, rotation at the gravitational radiation-reaction instability (at which emission of gravitational waves set in which slows the star down). Part three of this article deals with the properties of hypothetical strange stars. Specifically we investigate the amount of nuclear solid crust that can be carried by a rotating strange star, and answer the question whether such objects can give rise to the observed phenomena of pulsar glitches, which is at the present time the only astrophysical test of the strange-quark-matter hypothesis

[en] The impact of the nuclear equation of state on the properties of rotating neutron stars from two different sources, stable rotation at the general relativistic Kepler period and rotation at the gravitational radiation-reaction driven instability mode, is analyzed. For this purpose models of rotating neutron stars are constructed in the framework of Einstein's theory of general relativity by applying a refined version of Hartle's perturbative stellar structure equations. The investigation is based on a representative collection of a total of seventeen nuclear equations of state, covering both non-relativistic as well as relativistic ones. 41 refs., 3 figs., 2 tabs

[en] Models of rotating neutron stars are constructed in the framework of Einstein's theory of general relativity. For this purpose a refined version of Hartle's method is applied. The properties of these objects, e.g. gravitational mass, equatorial and polar radius, eccentricity, red- and blueshift, quadrupole moment, are investigated for Kepler frequencies of 4000 s^-1 ≤ Ω_K ≤ 9000 s^-1. Therefore a self-consistency problem inherent in the determination of Ω_K must be solved. The investigation is based on neutron star matter equations of state derived from the relativistic Martin-Schwinger hierarch of coupled Green's functions. By means of introducing the Hartree, Hartree-Fock, and ladder (Λ) approximations, models of the equation of state derived. A special feature of the latter approximation scheme is the inclusion of dynamical two-particle correlations. These have been calculated from the relativistic T-matrix applying both the HEA and Bonn meson-exchange potentials of the nucleon-nucleon force. The nuclear forces of the former two treatments are those of the standard scalar-vector-isovector model of quantum hadron dynamics, with parameters adjusted to the nuclear matter data. An important aspect of this work consists in testing the compatibility of different competing models of the nuclear equation of state with data on pulsar periods. By this the fundamental problem of nuclear physics concerning the behavior of the equation of state at supernuclear densities can be treated

No abstract available

[en] This comprehensive, illustrated report for the Swiss Federal Office of Energy (SFOE) takes a look at the results of a study with respect to industrial energy consumption which provided scenarios for future Swiss energy consumption. Four scenarios were elaborated: Continuation of present policy, increased co-operation between state and industry, more ambitious energy policy priorities and a scenario with even more ambitious goals - the so-called '2000 Watt Society'. For each of these scenarios several variants and a selection of sub-variants were defined, including increased prices, higher gross domestic product GDP, warmer climate and various carbon levies. The specific energy consumption of 16 different industrial sectors is examined and the effects of the various scenarios on several factors are considered. Data and results are presented in tabular and graphical form. Various measures that could influence energy consumption are listed and discussed, as are the modelling methods employed and the plausibility of the results obtained