Showing papers by "Johannes Kepler University of Linz published in 1976"
TL;DR: A characterization theorem is proved for a certain type of bases of polynomial ideals whose usefulness stems from the fact that a number of computability problems in the theory of poynomial ideals is reducible to the construction of bases in this type.
Abstract: We define a certain type of bases of polynomial ideals whose usefulness stems from the fact that a number of computability problems in the theory of polynomial ideals (e.g. the problem of constructing canonical forms for polynomials) is reducible to the construction of bases of this type. We prove a characterization theorem for these bases which immediately leads to an effective method for their construction.
308 citations
TL;DR: A uniqueness theorem is given for Gröbner-bases of polynomial ideals and it is shown that it is effectively decidable whether a given basis is a (minimal normed) GröBner-basis.
Abstract: We give a uniqueness theorem for Grobner-bases of polynomial ideals and show that it is effectively decidable whether a given basis is a (minimal normed) Grobner-basis. Incidentally, we show how our methods may be applied to decide α ≤ β for given polynomial ideals α and β.
73 citations
TL;DR: In this paper, the critical behavior of elastic phase transitions of second order, where the order parameter is a strain component and the soft mode is an acoustic mode, is studied by the RNG method.
Abstract: The critical behaviour of elastic phase transitions of second order, where the order parameter is a strain component and the soft mode is an acoustic mode, is studied by the RNG method A classification of the different types of elastic phase transitions in three-dimensional crystals is given and two general models are introduced for these transitions which are suitable for an investigation by the RNG method Critical exponents of thesed-dimensional models with anm-dimensional subspace of soft directions are calculated by thee-expansion as a function ofd andm The critical dimensionality is shifted to lower values in comparison to spin models In systems where softening occurs only in a one-dimensional subspace the critical behaviour is classical in three dimensions, for those where softening occurs in a two-dimensional subspace logarithmic corrections to the classical behaviour are found
68 citations
TL;DR: In this article, the Hall effect and transverse magnetoresistance of n and p-type PbTe with carrier concentrations as low as 1.8×1016 cm−3 in magnetic fields up to 15 T were measured.
Abstract: We report measurements of the Hall effect and the transverse magnetoresistance of n‐ and p‐type PbTe with carrier concentrations as low as 1.8×1016 cm−3 in magnetic fields up to 15 T. The data rule out the existence of deep impurity levels and are, however, not in contradiction with the presence of resonant levels due to Pb or Te vacancies within the bands according to the model by Parada and Pratt.
31 citations
TL;DR: In this paper, a general theory of a LLL interferometer with arbitrary absorption is given in the context of plane wave theory as well as in the spherical theory, and reflection properties are discussed comparing X-ray and neutron interferometry.
Abstract: A general theory of a LLL interferometer with arbitrary absorption is given in the context of plane wave theory as well as in the spherical theory. Reflection properties are discussed comparing X-ray and neutron interferometry.
Es wird die Theorie eines symmetrischen LLL-Interferometers unterschiedlicher Absorption entwickelt, wobei sowohl die Theorie ebener Wellen, als auch die spharische Theorie behandelt werden. Die Reflexionseigenschaften werden diskutiert, und die Unterschiede zwischen Rontgen- und Neutronen-Interferometern hervorgehoben.
24 citations
TL;DR: In this article, a d-dimensional model with an m-dimensional subspace of soft directions is introduced and the static and dynamic critical exponents are calculated as a function of d and m.
19 citations
TL;DR: In this article, a model-dielectric function according to Wallace was used, including frequency and magnetic field dependences of the carrier damping and the effective masses, for the PbTe expitaxial films.
Abstract: Magnetoreflection spectra of n-PbTe in the wave-number region 20 to 200 cm−l are measured with magnetic fields up to 16 T. The PbTe expitaxial films grown on BaF2 and NaCl substrates have rarrier concentrations between 6 × 1016 and 5 × 1017 cm−3. For the PbTe a model-dielectric function according to Wallace is used, including frequency and magnetic field dependences of the carrier damping and the effective masses. For small magnetic fields the nonparabolicity of the conduction band can be described by a two-band Kane model. At higher magnetic fields the influence of polaron coupling is observed.
Magnetoreflexionsspektren an n-PbTe werden im Spektralbereich von 20 bis 200 cm−1 in Magnetfeldern bis zu 16 T gemessen. Die epitaktisch auf BaF2- und NaCl-Substraten aufgewachsenen PbTe-Filme haben Ladungstragerkonzentrationen zwischen 6 × 1016 und 5 × 1017 cm−3. Fur PbTe wird ein Modell nach Wallace fur die dielektrische Funktion benutzt, das Frequenz- und Magnetfeldabhangigkeit der Dampfung und der effektiven Massen der freien Ladungstrager enthalt. Fur kleine Magnetfelder kann die Nichtparabolizitat des Leitungsbandes durch ein Zwei-Band Kane-Modell beschrieben werden. Bei hohen Peldern wird der Einflus der Polaronen-Kopplung beobachtet.
17 citations
TL;DR: In this article, a detailed information on the variation of the optical constants and particularly of TO phonon softening with decreasing lattice temperature is obtained for samples with n ≈ 0.3−3.0 × 1017 cm−3, and the frequencydependence of the carrier collision time was investigated.
16 citations
8 citations
TL;DR: In this paper, the minority carrier lifetime τ of p-PbTe was determined by measuring the transient behaviour of PbTe-diodes by a step pulse recovery method.
6 citations
TL;DR: In this paper, it was proved that there exist real n × n -matrices of determinant unity which are not DOTU-matrices, and that such matrices are not determinant monotone matrices.
01 Jan 1976
TL;DR: The paper introduces some ideas of general systems theory which successfully establish a set theoretical and algebraic framework for construction and realization of dynamical systems.
Abstract: The paper introduces some ideas of general systems theory which successfully establish a set theoretical and algebraic framework for construction and realization of dynamical systems. In chapter 4, these concepts are used to explain the linear-realization theory of Kaiman for the discrete-time case. Chapter 5 is devoted to general ideas on the state concept and dynamical generation of processes.
TL;DR: In this paper, the currentvoltage characteristics of copper were measured up to current densities of 2 × 10 9 A/cm 2 at 300 K. Within the experimental accuracy of 1.5% no deviation from Ohm's law was found.
TL;DR: In this article, an automatic control and registration system for a flat crystal spectrometer is described which permits quantitative measurements of proton induced X-ray spectra in three modes of operation: PRESET CHARGE, PRESET TIME, and PRESET COUNTS.
TL;DR: In this paper, a realisierte kugelsonde wird beschrieben und es werden Meβbeispiele diskutiert, e.g., Beurteilung von Meβfehlern und Abweichungen von theoretischen Annahmen.
TL;DR: In this paper, the Wigner density function of a Bose gas of quasiparticles (magnons) is derived in the region of linear response, using a simple factorization procedure to transform the Hierarchy equations into a system which can be solved iteratively.
Abstract: A kinetic equation for the Wigner density function of a Bose gas of quasiparticles (magnons) is derived in the region of linear response. The method uses a simple factorization procedure to transform the Hierarchy equations into a system which can be solved iteratively. The first nontrivial approximation is examined in the limit of slow time and space variation. It gives the linearized Boltzmann equation in the form assumed in the Landau theory. The correction of lowest order in (coupling constant × density) is shown to be a correction to the Born approximation of the scattering cross section.