bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantum Statistics of Multimode Optical Bistability with Trilinear interaction
Authors: Germey K. , Schütte F.‐J. , Tiebel R. , Worlitzer K. 
Published: May 2007

AbstractAn externally driven light mode in a ring cavity may show multistable behaviour if linear losses and dispersive nonlinear coupling compete with each other. The paper considers the trilinear (sum frequency) system with two externally driven modes which shows bistability simultaneously in these two modes. It is described in a fully quantum manner. The master equation and the Fokker‐Planck equation for the Glanmber‐Sudarshan quasi‐probalbility are deduced with appropriate consideration of fluctuations. A closed steady solution of the Fokker‐Planck equation is given for one mode only under strong restrictive assumptions.
Nonequilibrium Sources of Hydrodynamic Fluctuations Mutual Influence of Hydrodynamic Motion and Nonequilibrium Fluctuations on the Kinetic Coefficients
Authors: Klimontovich Yu. L. 
Published: May 2007

AbstractFrom generalized expressions for the entropy production the kinetic coefficients in the hydrodynamic equations are determined taking into account the mutual influence of the hydrodynamic motion and the fluctuations. Nonlinear effective and turbulent kinetic coefficients are obtained. The usefulness of the introduced coefficients is demonstrated for boundary layer and tube flows.
Thermodynamic Functions of Nonideal Alkali Plasmas
Authors: Richert W. , Insepov S. A. , Ebeling W. 
Published: May 2007

AbstractThe thermodynamic functions are analyzed on the basis of the present theoretical knowledge. Padé approximations are constructed which have the correct limiting behaviour: Debye law with quantum corrections in the high temperature limit, Gell‐Mann‐Brueckner law and Madelung law in the low‐temperature limit. The region of partial ionization (bound state valley in the n‐T‐plane) is studied by using the mass action law.
Rudolf Clausius. Ein Versuch, ihn zu verstehen
Authors: Schöpf Hans‐Georg 
Published: May 2007

AbstractEs wird dargelegt, daß Clausius' Originalarbeiten über die Begründung des zweiten Hauptsatzes schwerlich vom Standpunkt konventioneller Lehrbücher verstanden werden können. Vielmehr erweist sich eine mit einem quasi‐ökonomischen Modell arbeitende Denkweise als Schlüssel zum Verständnis.
Ladungsträgerstreuung an polaren Grenzflächenphononen im 2‐dimensionalen Elektronengas einer Halbleitergrenzfläche: Anwendung auf die Inversionsschicht eines MOS‐FET
Authors: Bechstedt F. , Enderlein R. 
Published: May 2007

AbstractDie Ladungsträger des 2‐dimensionalen Elektronengases einer Halbleitergrenzfläche unterliegen einer zusätzlichen Streuung an polaren Grenzflächenphononen. Das Energiespektrum dieser Phononen und die Raten für die Streuung an ihnen werden in der vorliegenden Arbeit auf einer einheitlichen Grundlage – der Selbstenergie des mit dem Gitter polar wechselwirkenden Elektronengases – berechnet. Für die Inversionsschicht eines MOS‐FET erweist sich die Streuung an den polaren Grenzflächenphononen des SiO2Si‐Übergangs bei hinreichend hohen Ladungsträgerenergien bzw.‐konzentrationen als effektiver Konkurrenzprozeß zu den bisher in der Literatur ausschließlich diskutierten Streuprozessen. Die Ergebnisse werden mit experimentellen Beweglichkeiten für den n‐Kanal eines MOS‐FET verglichen.
Theoretical Studies of the Configuration and Association Energies of Point Defect Aggregates in Alkali Halide Crystals
Authors: Berg G. , Fröhlich F. , Pippel A. 
Published: May 2007

AbstractThe aggregation of dipoles consisting of a divalent metal impurity and a cation vacancy in alkali halide crystals is determined mainly by the association energy connected with the formation of the special types of aggregates. It is shown that also larger aggregates (complexes of four and more dipoles) are important to characterize the equilibrium state. Therefore a simple computational method will be presented to estimate atomistically the association energy of such aggregates. A comparison with results from the literature valid for little aggregates (mainly dimers and trimers) confirms the applicability of the proposed procedure.
The Role of “Rotational Freezing” in the Polarisation‐Dependent Two‐Photon Excitation of Triply Degenerate Vibrations in Spherical‐Top‐Molecules
Authors: Ritze H.‐H. 
Published: May 2007

AbstractUnder certain circumstances at low rotational temperatures the multiphoton excitation probabilities of vibrational‐rotational levels in high‐symmetric molecules do not depend on the rotational quantum numbers J and M of the initially populated levels. Then the rotation of the molecule as a whole is “frozen”. This has the consequence that during the absorption process the photon spin is not transferred to the molecular rotation but to the molecular vibration. In more detail the two‐photon A1g(v = 0) → A1g(v = 2) transition in SF6 at 944.5 cm−1 is theoretically studied: If the “average lifetime” in the intermediate (v = 1)‐level is small compared with the effective molecular rotation period the considered transition is forbidden for circularly polarised light. Further the excitation process of the Eg(v = 2) and F2g(v = 2) vibrational levels is investigated; it is discussed under which conditions it is not necessary to consider the rotational degrees of freedom for a calculation of transition dipole moments.
Electric Dipole Oscillator Strengths and Radiative Lifetimes in the Boron Isoelectronic Sequence
Authors: El‐Sherbini Th. M. , Farrag A. A. , Mansour H. M. , Rahman A. A. 
Published: May 2007

AbstractOscillator strengths for the 2s2ns(2S) −2s2mp(2P), (n = 3–6, m = 2–6) and 2s2np(2P) −2s2md(2D), (n = 4–6, m = 3–5) transitions in B I sequence are calculated in LS‐coupling scheme. The Coulomb approximation is used in calculating the radial part of the wave functions, while the angular part is determined using the Racah technique. Lifetimes of the ns(2S) and np(2P), (n = 3–6) excited states are evaluated and compared with previous results from beamfoil experiments.
On the Theory of Gravitational Field in Finsler Spaces
Authors: Ikeda Satoshi 
Published: May 2007

AbstractSome structural considerations are made on the Finslerian gravitational field: A Finslerian metrical structure such as gλχ(x, y) = γλχ(x) + hλχ(x, y) is proposed, where γλχ denotes the Riemann metric of Einstein's gravitational field, while hλχ the Finsler metric induced by the Riemann metric hij(y) of the internal field; The intrinsic behaviour of the internal variable y, which is expressed as ȳi = K(x, y) yj in the internal field, is grasped by the Finslerian parallelism δyi (=0), which is reflected in the spatial structure of the external gravitational field by the mapping relation δyχ = e(x) δyi. The whole metrical Finsler connection D for gλχ(i.e., Dgλχ = 0) is determined by taking account of the intrinsic behaviour δyχ.
Photodetachment of Electrons Compounded to Excited Hydrogen Atoms as Source of Absorption Features in Magnetic Stars?
Authors: Oetken L. 
Published: May 2007

AbstractScattering of thermal electrons at excited hydrogen atoms forms resonances, from which absorption features may arise, if the resonances donot decay by electron emission before; these absorption features agree in wavelengths with those observed in normal early type stars (Teff ∼ 104 K) and predominantly in magnetic stars. It is shown that the conditions for the formation of the resonances, the quasistable states of H−, are just most convenient for the stars in question.
Oscillations in the Determination of Renyi Dimension
Authors: Thümmel Ottfried 
Published: May 2007

AbstractTo describe the degree of chaos of a strange attractor created by a nonlinear map, GRASSBERGER [1] revived Renyi Dimension Dq which is a common generalization of both metric capacity D0 and information dimension D1. But often, the numerical determination of Dq is complicated by an oscillating effect first investigated by BADII and PUOLITI [5] for a dimension similar to D0. This effect is studied in the present paper. We consider the conditions for the appearance of oscillations and the dependence on q, and we give some numerical examples.
Dependence of the Three‐Nucleon Binding Energy on Some Different Effects
Authors: Osman Ahmed , Ramadan S. 
Published: May 2007

AbstractThe bound state of three‐nucleon system is studied as a three‐body problem which is solved following the different approaches of the Faddeev formalism as well as the unitary pole approximation. The three‐body problem is reduced to a set of coupled integral equations by using separable approximations. Numerical calculations are carried out for the resulting integral equations and the separable expansion. In the present work, we calculate the ground‐state binding energy of the bound three‐nucleon system 3H. The main interest of the present work is to investigate the sensitivity of the three‐nucleon binding energy to different effects. For this reason, we study the dependence of this energy on different forms of local and separable nucleon‐nucleon potentials, the effective range of the nucleon‐nucleon interaction, and on the percent of the D state in the deuteron wave function. Also we test the sensitivity of the three‐nucleon binding energy to the considered number of terms from the separable expansion.
Einstein's Materialism and Modern Tests of Quantum Mechanics
Authors: Vigier J. P. 
Published: May 2007

AbstractAfter a presentation of Einstein's and Bohr's antagonistic point of view on the interpretation of Quantum Mechanics an illustration of their conflicting positions in the particular case of Young's double slit experiment is presented. It is then shown that in their most recent form (i. e. time dependent neutron interferometry) these experiments suggest (if one accepts absolute energymomentum conservation in all individual microprocesses) that Einstein was right in the Bohr‐Einstein controversy.
Stochastic Quantization of Einstein‐Cartan Gravitational Theory
Authors: Ivanenko D. , Budylin S. , Pronin P. 
Published: May 2007

AbstractWe apply the stochastic quantization method to Einstein‐Cartan gravitational theory. The stochastic propagators are calculated and the cooperation of modes in such a theory is investigated. It was shown that in equilibrium limit our result is equivalent to the propagator for the symmetric part of tetrads.
Entropy of a Two‐phase Mixture
Authors: Schulz H. , Reinhardt H. , Kämpfer B. 
Published: May 2007

AbstractThe isentropic expansion of a blob of nuclear matter towards the two‐phase instability region is studied by considering two extreme conditions: the instantaneous development of the phase transition and the spinodal decomposition. We show that the experimentally observed entropy values of light clusters give evidence for the onset of a liquid‐gas phase transition in heavy ion and proton induced reactions, but to be more conclusive the disassembly of relatively cold nuclear systems has experimentally to be investigated in more detail.
Sum Rules in the Quark Model
Authors: Abbas Afsar 
Published: May 2007

AbstractWith the help of various sum rules we look into the spin‐isospin excitations in nuclei within a framework of the quark model. The effect of Pauli correlations is explicitly taken care of. In agreement with the experiments we find negligible amount of M1 strength in heavy nuclei. This is explained in terms of the Fermi gas model.
Translation Gauge Fields and Space‐Time Dislocations
Authors: Sardanashvily G. , Gogberashvily M. 
Published: May 2007

AbstractGauge fields of Poincaré translations define particular nongravitation structure on a space‐time, which can be treated as sui generis space‐time dislocations. Their source is the canonical energy‐momentum tensor of matter, and these dislocations can introduce some corrections to standard values of gravitation effects, e. g. the Yukawa type corrections to the Newtonian gravitation potential.
Definition of the Degree of Order in Selforganization Processes
Authors: Klimontovich Yu. L. , Bonitz M. 
Published: May 2007

AbstractSelforganization processes controlled by two pumping parameters are studied. The question of thermodynamic equilibrium in nonlinear pumped systems is investigated. Using the entropy statement formulated in a recent paper the degree of order of steady states is defined. It is shown that those systems can be optimated following various principles. For illustration, selfoscillations of nonlinear oscillators with two pumping parameters are studied.
Rearrangement Collisions between Four Identical Particles as a Four‐Body Problem
Authors: Osman Ahmed 
Published: May 2007

AbstractNuclear reactions between composite particles with rearrangement processes are considered. The cluster model is used in describing the structure of the nuclei. With this structure we have in the initial channel as well as in the final channel, four interacting particles. These reactions are studied as a four‐body problem. The scattering amplitudes are approximated by using a separable expansion for the separable potential model. The four‐body equations are reduced to integral equations in the form of exact effective two‐particle Lippmann‐Schwinger equations. These equations are solved by standard methods in a form suitable for numerical calculations. The present four‐body treatment is applied calculating the differential cross‐sections for different scattering and transfer nuclear reactions. Distorted wave Born approximation calculations are used in calculating the angular distributions. The present theoretical calculations are in good agreement with the experimental angular distributions.
Pade‐Approximants for the Electron Gas and for Symmetrical Plasmas
Authors: Ebeling W. , Lehmann H. 
Published: May 2007

AbstractThe range of validity for several Pade‐formulae for thermodynamic functions is checked in comparison with most recently available numerical data. Landscapes of maximum deviation are plotted. Application to symmetrical electron‐positron and electron‐hole plasmas is performed. An evaluation of the critical data for the droplet transition in semiconductors is given.
The Feynman integrand for the perturbed harmonic oscillator as a Hida distribution
Authors: Cunha Mário , Drumond Custódia , Leukert Peter , Silva José Luís , Westerkamp Werner 
Published: May 2007

AbstractWe review some basic notions and results of White Noise Analysis that are used in the construction of the Feynman integrand as a generalized White Noise functional. We show that the Feynman integrand for the harmonic oscillator in an external potential is a Hida distribution.
Determination of transition curves of high‐Tc superconductors by phase contrast microscopy
Authors: Kriebel Cl. , Hoffels O. , Borowski R. , Gottschalk H. , Alexander H. , Wohlleben D. 
Published: May 2007

AbstractA new method which allows the detection of the superconducting phase transition of high‐Tc superconductors (HTSC) on a microscopic scale is reported. Micro‐size holes in thin foils of superconducting material are examined in a transmission electron microscope at varying temperatures. The superconducting transition induces small changes in the image intensity within the holes, which can be detected by using electronic image analysis. Superconducting transition curves are then obtained for various types of high‐Tc superconductors and for given values of the applied magnetic field.
Kapitza phonon transmission from clean H‐silicon(111) surfaces into liquid helium
Authors: Wichert K. H. , Reimann C. , Blahusch G. , Kinder H. 
Published: May 2007

AbstractWe have studied the phonon transmission from ultraclean Si(111) surfaces into liquid helium by the phonon pulse technique. Reflection experiments and angular resolving transmission experiments were performed to measure the absolute value of the transmission coefficient and its dependence on the phonon emission angle into the solid. Clean samples etched conventionally in dilute HF show a significant anomalous transmission. An additional etch step in highly buffered HF (i.e., NH4F) with a pH‐value of 7.8 reduces the transmission coefficient drastically. Local inhomogeneities of the transmission coefficient caused by the deposition of water molecules on the surface could be visualized by the enhanced transmission. We found that the observed anomalous transmission is caused by mass defects.
Experiments with narrow movable beams of pulsed sound waves at 35 GHz
Authors: Knöll Th. , Weis O. 
Published: May 2007

AbstractOnly the study of absorption and angular dependent scattering of GHz and THz sound can give us detailed information about interaction processes of acoustical phonons. Therefore, the necessary techniques of sound generation, detection and undisturbed transmission to the target must be improved or to a large extent must still be developed. Corresponding attempts at 35 GHz are described. Sound‐beam topography allowed to study crystal defects and also showed us where transmission without scattering occurred. For the piezoelectric generation a reflex klystron was used feeding a planar Hertzian resonator. The needle‐like sound beams appeared as a double beam, each showing a minimum diameter of 35 μm for longitudinal polarized sound at an acoustic wavelength of 165 nm in X‐cut quartz and 320 nm in a‐cut sapphire. To obtain the smallest possible beam diameter for high resolution work, model calculations are presented for an excited fundamental Gaussian sound beam in an isotropic medium.
Transition from SU(2)L × SU(2)R × U(1)B‐L representation to SU(2)L × U(1)Y by q‐deformation and the corresponding classical breaking term of chiral U(2)
Authors: Bönisch R. 
Published: May 2007

AbstractThe minimal Standard Model exhibits a nontrivial chiral U(2) symmetry if the VEV and the hypercharge splitting Δ = (y‐y)/2 of right‐handed leptons (quarks) in a family vanish and Q = T0 + Y independently in each helicity sector. As a generalization, we start with SU(2)L × SU(2)R × U(1)(B‐L) and introduce Δ as a continuous parameter which is a measure of explicit symmetry breakdown. Values 0 ⩽ Δ ⩽ 1/2 take the neutral generator of the isospin ½ representation to the singlet representation, i.e. ‘deformes’ the LR representation into the minimal Standard one. The corresponding classical O(3)‐breaking term is a magnetic field perpendicular to the x3‐axis. A simple mapping on the fundamental Drinfeld‐Jimbo q‐deformed SU(2) representation is given.
Solution of the Eliashberg equations for a very strong electron‐phonon coupling with a low‐energy cutoff
Authors: Weger M. , Barbiellini B. , Jarlborg T. , Peter M. , Santi G. 
Published: May 2007

AbstractWe solve the Eliashberg equations for the case of an explicit k dependence of the interactions, and of the resulting self‐energies Σ1(k,ω), Σ2(k,ω). We consider a strong energy‐dependence of the electron‐electron scattering‐rate τ, which is associated with a strong energy‐dependence of the electron‐phonon matrix element g(k,k′). We characterize this energy‐dependence by a cutoff ζ1, which is of the order of the phonon frequency ωph. We find that we can account for a large number of unexpected features of the superconductivity of the cuprates by the BCS electron‐phonon theory, if we consider very large values of the McMillan coupling constant λph, and small values of the cutoff ζ1. Specifically, the Coulomb interaction is found not to depress Tc; the isotope effect is strongly reduced when ζ1 < ωph. We find solutions in which the gap function Δ(k, ω) has extended s‐wave symmetry but is very anisotropic. These large anisotropies are in good agreement with various experiments. We suggest that the underlying cause of the strong energy‐dependence is a very small electronic screening parameter at the Fermi surface; the electron‐phonon matrix element g is abnormally large, and this accounts for the high transition temperatures of the cuprates. An order of magnitude estimate suggests that the electron‐phonon mechanism can account for transition temperatures up to about 200 K. We thus propose a very‐strong‐coupling theory, in which the renormalization functions, in particular the energy‐renormalization X, depend very strongly on the superconducting gap Δ, and thus display a very strong temperature‐dependence between Tc and T = 0. An experimental manifestation of the very strong coupling with a small cutoff is a zero bias anomaly sometimes observed in tunneling experiments.
Reflection time as an eigenvalue problem
Authors: Bracher C. , Kleber M. 
Published: May 2007

AbstractStarting with wave packets, an eigenvalue equation is derived for the amount of time a particle needs for reflection from an impermeable potential barrier. The corresponding Hermitian operator TR is linear and diagonal in energy space. The eigenvalues are given by τ2(E) = ℏ \documentclass{article}\pagestyle{empty}\begin{document}$ \left\{ {\frac{{\partial \rho (E)}}{{\partial E}} + \frac{{\sin \rho (E)}}{{2E}}} \right\} $\end{document}, where ρ(E) is the phase shift for stationary reflection at fixed scattering energy E. The quantum mechanical reflection time τR(E) has a well defined WKB‐limit. For low scattering energies τR(E) is proportional to \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt E $\end{document} if weakly bound states are absent in the reflection region. However, if there is an empty weakly bound state it will transiently trap a slowly moving particle, causing a \documentclass{article}\pagestyle{empty}\begin{document}$ 1/\sqrt E $\end{document} divergence of the reflection time for E→0. We work out and illustrate the theory for various reflecting potentials. The method allows for a consistent treatment of the quantum mechanical Goos‐Hänchen time delay.
Mott‐Hubbard transition in a magnetic field
Authors: van Dongen P. G. J. , Leinung C. 
Published: May 2007

AbstractWe study the density of states (DOS) as a function of the interaction U in the half‐filled simplified Hubbard model in a magnetic field. This model is considered on the Bethe lattice in the limit of high dimensions. We show that the DOS can be calculated exactly, and that many of its properties have an astonishingly simple form. In particular, the DOS can be investigated explicitly in the limits of weak and strong coupling and near the metal‐insulator transition. E.g., we find an explicit result for the critical value Uc, at which the metal‐insulator transition occurs, as a function of the magnetization. The relation between the magnetization and the magnetic field is calculated numerically. An important result is that the metal‐insulator transition, occurring in the model with B = 0, is continuously connected to the metal‐insulator transition in the subspace of single spin flips.
On the interbasis expansion for the Kaluza‐Klein monopole system
Authors: Grosche C. , Pogosyan G. S. , Sissakian A. N. 
Published: May 2007

AbstractWe study the interbasis expansion of the wave‐functions of the Kaluza‐Klein monopole system in the parabolic coordinate system with respect to the spherical coordinate system, and vice versa. We show that the coefficients of the expansion are proportional to Clebsch‐Gordan coefficients. We analyse the discrete and continuous spectrum as well, briefly discuss the feature that the (reduced) Kaluza‐Klein monopole system is separable in three coordinate systems, and the fact that there are five functionally independent integrals of motion, respectively observables, a property which characterizes this system as super‐integrable.
Anisotropy of the mixed‐state resistance of Tl2Ba2CaCu2O8 single crystals
Authors: Weidinger A. , Seng P. , Tidecks R. , Samwer K. , Yu. Logvenov G. , Kolesnikov N. N. 
Published: May 2007

AbstractThe electrical resistance of single crystals of the high‐temperature superconductor Tl2Ba2CaCu2O8 has been measured as a function of the angle θ between the direction of the magnetic field and the current‐carrying CuO2‐planes. The resistance is maximal for θ = 90° (B⟂CuO2‐planes) and decreases to a minimum at θ = 0°. For small angles an anomalous enhancement of the resistance is found. While the general shape of the resistance is generated by the motion of “pancake vortices” in the CuO2‐planes, the anomaly is due to “Josephson vortices” moving perpendicular to the planes.