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Showing papers by "Technical University of Dortmund published in 1979"


Journal ArticleDOI
TL;DR: A comprehensive review of the known classical solutions of gauge theories is presented in this article, which follows the historical development of this subject from its beginning (the first explicit solution was an imbedded Abelian static Coulomb solution) up to the most recent work in the field (in particular the solutions which represent monopoles, instantons, and merons).
Abstract: A comprehensive review of the known classical solutions of $\mathrm{SU}(2)$ gauge theories is presented. The author follows the historical development of this subject from its beginning (the first explicit solution found was an imbedded Abelian static Coulomb solution) up to the most recent work in the field (in particular the solutions which represent monopoles, instantons, and merons). As well as being a detailed survey, this article is intended to serve as a self-contained introduction to the subject.

351 citations


Journal ArticleDOI
TL;DR: In this article, the neutrino energy range 30-200 GeV was investigated and the results were in agreement with the expectations of the quark parton model and QCD.
Abstract: We present results on charged current inclusive neutrino and antineutrino scattering in the neutrino energy range 30–200 GeV. The results include a) total cross-sections; b)y distributions; c) structure functions; and d) scaling violations observed in the structure functions. The results, as well as their comparison with the results of electron and muon inclusive scattering, are in agreement with the expectations of the quark parton model and QCD.

126 citations


Journal ArticleDOI
TL;DR: Measurements of observers’ sensitivity to light that was modulated sinusoidally at frequencies between 0·1 and 50 Hz suggest that the earlier c.f. studies underestimate the amount of binocular interaction in the detection of flicker.
Abstract: Sherrington's (1904) study of binocular flicker was extended by measuring observers' sensitivity to light that was modulated sinusoidally at frequencies between 0·1 and 50 Hz. Compared with the condition in which both eyes are stimulated in-phase, about 40% more modulation is needed to detect high-frequency flicker when the two eyes are stimulated in counterphase; at low frequencies this difference is even greater. These results suggest that the earlier c.f.f. studies underestimate the amount of binocular interaction in the detection of flicker.

101 citations


Journal ArticleDOI
TL;DR: In this article, the first experimental observation of "slow" pulse propagation in the exciton-polariton resonance of a direct-gap semiconductor was reported, where the propagation delay of short light pulses transmitted through a 3.7-m-thick GaAs crystal was measured directly with a cross-correlation technique.
Abstract: This paper reports the first experimental observation of "slow" pulse propagation in the exciton-polariton resonance of a direct-gap semiconductor. The propagation delay of short light pulses transmitted through a 3.7-\ensuremath{\mu}m-thick GaAs crystal was measured directly with a cross-correlation technique. Polariton group velocities from $\frac{{c}_{\mathrm{vac}}}{3.6}$ down to $\frac{{c}_{\mathrm{vac}}}{2000}$ were found when the wave-packet center frequency was tuned through the $n=1$ exciton resonance.

95 citations



Journal ArticleDOI
TL;DR: In this paper, the properties of perovskite type CsPbCl3, C sPbBr3 and thier mixed crystals were analyzed in the framework of an empirical LCAO-band model.

63 citations


Journal ArticleDOI
TL;DR: In this article, the production of a charmed baryon has been observed in pp collisions at the CERN ISR, with a sharp peak at 2.26 GeV/c2 in the decay mode Λ+c → K ∗0 p in events triggered with a forward K− meson.

54 citations


Journal ArticleDOI
TL;DR: In this article, moments of the nucleon valence structure function measured in high Q 2 ν FE scattering, supplemented by data from deep inelastic eD scattering, are presented.

48 citations


Journal ArticleDOI
TL;DR: In this article, the authors presented a detailed two-photon spectrum of the even-parity excitons of the yellow series in the effective mass Hamiltonian and showed evidence for a strong mixing between the yellow and the green series.
Abstract: This Letter presents for the first time a detailed two-photon spectrum of the even-parity excitons of the yellow series in ${\mathrm{Cu}}_{2}$O. Contrary to one-photon data, it is possible to measure directly $S$ and $D$ exciton contributions without applying external perturbations. The two-photon spectrum gives evidence for a strong mixing between the yellow and the green series which is explained by exchange interaction and nondiagonal parts in the effective-mass Hamiltonian.

42 citations


Journal ArticleDOI
TL;DR: In this paper, the authors measured the Knight shift and spin-lattice relaxation time of tellurium single crystals between room temperature and the melting point (724 K) using pulsed-NMR methods.
Abstract: The Knight shift and spin-lattice relaxation time of $^{125}\mathrm{Te}$ in tellurium single crystals have been measured between room temperature and the melting point (724 K) using pulsed-NMR methods. Over the entire temperature range, the temperature dependence of the Knight shift is found to be determined completely by the intrinsic conductivity associated with thermally created conduction electrons in the conduction band, and the band-gap energy is determined. The spin-lattice relaxation time shows different temperature variations in two different regions: below 420 K ("low-temperature region"), spin-lattice relaxation is due to the conduction electrons (thus yielding information on the gap energy), while above 420 K ("high-temperature region") the relaxation process is due to the self-diffusion of Te atoms. Our Knight-shift results are found to agree quantitatively with a modified Knight-Korringa relation valid for semiconductors, which was originally derived by Bloembergen and which is reconsidered in the theoretical part of this article. The electronic contribution to spin-lattice relaxation is analyzed in terms of Hebel and Slichter's single spin-temperature theory as applied to semiconductors. The same gap energy, ${E}_{g}=0.30$ eV, is found from both our Knight-shift and spin-lattice relaxation data. The self-diffusion properties of tellurium as extracted from our high-temperature relaxation studies will be the subject of a subsequent article.

40 citations


Book ChapterDOI
01 Jan 1979
TL;DR: In this article, a review of recent applications of the scattering theoretical method (STM) to a variety of realistic systems is presented, with particular emphasis on semiconductor surfaces and interfaces.
Abstract: In this paper electronic structure theory for semiconductor surfaces and interfaces is reviewed with particular emphasis on recent applications of the scattering theoretical method (STM) to a variety of realistic systems. Easy intelligible and physically appealing pictures of general surface and interface electronic properties are developed in the discussion of the results by directly correlating the changes in bonds at surfaces or interfaces with the resulting changes in bands and densities of states. Bound states, resonances and antiresonances are introduced and discussed on a very intuitive level and the scattering theoretic method is shown to be a natural and thus very powerful technique to calculate a wealth of experimentally interesting information in a very efficient way. The systems discussed in this article range from ideal, relaxed and reconstructed semiconductor surfaces over interfaces in heterojunctions, overlayer systems and superlattices to defects at surfaces or interfaces. Comparison with experimental data is made wherever possible.

Journal ArticleDOI
TL;DR: In this article, a static low-temperature cluster above the phase transition in the H-bonded antiferroelectric squaric acid was observed by high-resolution NMR spectroscopy.
Abstract: Static low-temperature clusters above the phase transition in the H-bonded antiferroelectric squaric acid are observed by high-resolution $^{13}\mathrm{C}$ NMR spectroscopy. Cluster formation and decay at different temperatures is observed to depend strongly on the type of impurity center inducing the cluster. Connection with the appearance of a "central peak" in light and neutron scattering is drawn.

Journal ArticleDOI
01 Dec 1979-Metrika
TL;DR: In this article, the asymptotic distribution for a certain class of functionals of distribution functions is derived, and the results are applied to the Lorenz-curve and the Gini-measure as special cases of the abovementioned functionals.
Abstract: The asymptotic distribution for a certain class of functionals of distribution functions is derived. This result is used to give distribution free asymptotic confidence intervals for these functionals; for this purpose, a strongly consistent estimate for the asymptotic variance is constructed. These results are applied to the Lorenz-curve and the Gini-measure as special cases of the abovementioned class of functionals.

Journal ArticleDOI
TL;DR: Geminal tin-tin coupling constants 2J(SntCSn) were presented for a number of organotin compounds and discussed in terms of other coupling data Chemical shift data have also been obtained; particularly noteworthy is the tin chemical shift difference of ca 40 ppm between the two tin nuclei in 7,7-bis-(trimethylstannyl)norcarane.

Journal ArticleDOI
01 Sep 1979
TL;DR: In this article, the authors measured the coherent scattering lengths of atoms in fm with the interferometer of the Neutron Interferometer (NIE) and obtained the following results:
Abstract: With the neutron interferometer, measurements of the coherent neutron scattering lengths by various gases have been performed. We get the following numbers for the bound coherent scattering lengths for atoms (in fm):bc(H) =−3.64(3),bc(D)=6.55(8),bc(He−3)=5.74(7),bc(He)=3.26(3),bc(N)=9.30(8),bc(O)=5.83(5),bc(Ne) =4.63(4),bc(Ar)=2.07(2),bc(Kr)=7.52(6),bc(Xe)=4.69(4). In some cases greater accuracy is achieved in comparison with recommended values from the literature. The absolute values for hydrogen and deuterium measured with gaseous samples, are about 2% smaller than the values measured with liquids and other reference values.

Journal ArticleDOI
TL;DR: In this article, the results of two different computer experiments for the dc-conductivity at zero temperature for a one dimensional disordered system with site energies distributed randomly over a finite energy interval are presented.

Journal ArticleDOI
TL;DR: In this article, the spatial properties of polariton fluorescence are shown to be of crucial importance to determine polariton lineshapes, and the spatial dependence of the polariton line and its spatial properties is investigated.

Book ChapterDOI
01 Jan 1979
TL;DR: In this article, it was shown that the smallest number d + 2 is the smallest which has the stated property, i.e., the set of disjoint subsets whose convex hulls have a common point.
Abstract: Radon’s theorem is one of the cornerstones of combinatorial geometry. It asserts that each set of d + 2 points in Rd can be expressed as the union of two disjoint subsets whose convex hulls have a common point. Moreover, the number d + 2 is the smallest which has the stated property.

Journal ArticleDOI
TL;DR: In this paper, the background from charged-current processes with one π or K meson of the hadronic shower decaying into μ − ν (or μ + μ) was used to obtain neutrinos a rate of prompt like-sign dimuon production of (3.4±1.8)×10 −5 relative to the rate of charged current events with the same cuts.

Journal ArticleDOI
TL;DR: In this article, the periodic Anderson model is replaced by the sum of two single-particle alloy Hamiltonians, the parameters of which have to be determined self-consistently.
Abstract: To describe the electronic properties of mixed valence compounds we study the periodic Anderson model within the frame of the alloy analog approximation. In this approach the model Hamiltonian is replaced by the sum of two single-particle alloy Hamiltonians the parameters of which have to be determined self-consistently. The alloy problem is solved within the coherent potential approximation. In contrast to other treatments of the periodic Anderson model this approximation scheme is exact in both trivially solvable limits of vanishing hybridization and Coulomb repulsion, respectively. For model parameters corresponding to a mixed valence situation only nonmagnetic solutions of the self-consistency equations exist. After discussing the limit of small hybridization analytically we numerically calculate the magnetic susceptibility and the electronic specific heat as a function of temperature for realistic values of the hybridization and Coulomb repulsion. The results are in very good qualitative agreement with experimental data.

Journal ArticleDOI
TL;DR: In this paper, the authors present a set of biochemically reasonable conditions for the rate laws which imply the existence of observable oscillations, which were obtained by linear stability analysis and computer simulation.
Abstract: Many models of open enzyme regulated systems are given by two first order differential equations of a certain type. We present a set of biochemically reasonable conditions for the rate laws which imply the existence of observable oscillations. A simple positive feedback mechanism is discussed as an example. Results on the allosteric model of glycolytic oscillations, which were formerly obtained by linear stability analysis and computer simulation, are extended and verified by mathematical proofs.

Journal ArticleDOI
TL;DR: The theorem of Gleason without positivity and separability condition was proved in this article without any positivity or separation condition, and the theorem was proved without any condition on the proof.
Abstract: The theorem of Gleason is proved without positivity and separability condition.


Journal ArticleDOI
TL;DR: In this article, the DASP detector at the DORIS storage ring was used to obtain new data for the reaction e + e − →ϒ(9.46) keV.

Journal ArticleDOI
TL;DR: In this paper, the authors used two perfect silicon crystal lamellae of high quality to detect the bending of neutron waves within an aluminium prism down to 10 −3 s of arc by observing the oscillatory fine structure of the rocking curve.

Journal ArticleDOI
TL;DR: In this paper, a lead-scintillator shower counter using a flourescent radiation converter for collecting scintillation light is described, and the uniformity of energy response and the spatial resolution have been measured.

Journal ArticleDOI
TL;DR: In this paper, the authors derived an expression for the hydrodynamic force and couple, respectively, which are exerted upon a particle in a simple shear flow, where the symmetry axis is parallel to the vorticity vector and the resulting translational slip velocity causes the particle to migrate out of the flow-shear plane in the direction of its pointed end.
Abstract: To study the motion of an arbitrary near sphere immersed in a homogeneous shear flow of an incompressible viscoelastic fluid we impose the restriction that the flow is dynamically and rheologically slow. This allows us to derive an expression for the hydrodynamic force and couple, respectively, which are exerted upon the particle. With the exception of elongational flows marked differences to the behavior in a newtonian fluid show up: sedimentation in a quiescent fluid is accompanied by a rotation until a stable terminal orientation is attained. For prolate spheroids the symmetry axis thus ends up parallel to the direction of the external force and perpendicular to it if the spheroid is oblate. In simple shear the difference between prolate and oblate spheroids manifests itself in the direction in which the rotating symmetry axis drifts (orbit-drift): prolate spheroids drift towards the orbitC = 0 while for oblate ones the drift is towardsC = 0. For deviations from the spheroidal shape (but still fore-aft symmetry) another orbitC * comes into play. Some particles drift towardsC * while others towardsC = 0 if initiallyC < C * and towardsC = ∞ if initiallyC > C *. If no longer matters whether the particle is slender or not. Although this is perhaps the most interesting result obtained one should also mention the behavior of an ovoid in simple shear. If the symmetry axis is parallel to the vorticity vector the resulting translational slip velocity causes the particle to migrate out of the flow-shear plane in the direction of its pointed end.

Journal ArticleDOI
01 Nov 1979
TL;DR: In this paper, a search based on structural groups is carried out for structural groups showing selective effects on the components of the system to be separated, and the resulting structural groups are then employed for the selection of real compounds as solvents.
Abstract: Fur Gemische, die sich wegen geringer Unterschiede in den Fluchtigkeiten ihrer Komponenten durch gewohnliche Rektifikation schwer trennen lassen, ist die extraktive Destillation eine Alternative. Bei der Betrachtung dieser Moglichkeit ist der wichtigste Schritt die Suche nach einem geeigneten Losungsmittel. Ein solcher Hilfsstoff mus die Fluchtigkeiten der einzelnen Komponenten in unterschiedlichem Mase beeinflussen. Ein quantitatives Kriterium. fur die Eignung des Losungsmittels ist das Verhaltnis des Aktivitatskoeffizienten der zu trennenden Komponenten bei unendlicher Verdunnung. Es kann mit Vorausberechnungsmethoden wie dem UNIFAC-Ansatz ermittelt werden. — Dazu wird folgender Weg eingeschlagen: Als erster Schritt wird mit Hilfe von UNIFAC und einer Datenbank die selektive Wirkung von Losungsmitteln unterschiedlicher Struktur untersucht. Diese Berechnungen lassen erkennen, welche funktionellen Gruppen die Selektivitat gunstig beeinflussen. Mit den so gewonnenen Informationen erfolgt dann die Auswahl von Losungsmitteln, die gleichzeitig praktische Anforderungen (z. B. Siedepunkt) erfullen. Anschliesend konnen die Dampf-Flussig-Gleichgewichte entweder mit Hilfe des UNIFAC-Ansatzes berechnet oder bei Vorliegen experimenteller Daten aus einer Datenbank entnommen werden. - Diese Vorgehensweise wird an einem Beispiel der Aliphaten/Aromaten-Trennung erlautert. For mixtures which are difficult to separate by ordinary distillation because components show small or no differences in their volatilities, extractive distillation is an alternative. In taking into consideration this possibility, the search for suitable solvents is the most important step. As a prerequisite such solvents must influence the volatilities of components to be separated in different degree. A quantitative criterion for the performance of solvents is the ratio of activity coefficients at infinite dilution in the solvent which may be evaluated by prediction methods such as UNIFAC. - For this purpose the following strategy is used. In a first step a search, based on UNIFAC parameters, is carried out for structural groups showing selective effects on the components of the system to be separated. The resulting structural groups are then employed for the selection of real compounds as solvents. VLE data for these solvents are then either calculated with the UNIFAC model or taken from a VLE data bank, if experimental data are available. - This procedure is demonstrated by an example from aliphatic/aromatic separation.

Journal ArticleDOI
TL;DR: In this article, the progres of numerical methods in the study of the Anderson transition over the last ten years are outlined, and the adaptation of the equation-of-motion method to calculate the conductivity is described.
Abstract: The progres of numerical methods in the study of the Anderson transition over the last ten years is outlined. The adaptation of the equation-of-motion method to calculate the conductivity is described, and results are presented for systems of up to 992 sites.

Journal ArticleDOI
TL;DR: Lower bounds for the number of different real eigenvalues as well as for real simple eigen values of a class of real irreducible tridiagonal matrices are given in this article.