bluuebunny/crossref_metadata_2025 huggingface dataset:
A RING OF JOSEPHSON-JUNCTIONS IN A MAGNETIC FIELD
Authors: Kusmartsev F. V.
Published: November 2004

We studied the magnetic properties of the ring of a Josephson junctions in a magnetic field at different capacitance of superconducting regions. We found that the capacitance which is the characteristic of the size of the superconducting region, does not change qualitatively the magnetic properties of the ring of junctions. At half-quantum of the flux through the ring there appears the magnetic phase transition which is characterised by the singularity in magnetization and in sucseptibility. At the transition there is the trapping of the one quantum of the flux by the ring. The interpretation of experiments, describing the inverse kinetic inductance as a function of a flux per plaquette of a lattice of two-dimensional arrays of the Josephson junctions is proposed. The new singularities in this dependency are predicted.
PLASMA-ASSISTED VACUUM-COATING PROCESSES
Authors: KIENEL GERHARD
Published: November 2004

For the properties of thin films produced in a vacuum the most important variable is the mobility of the particles in the course of condensation, which is dependent on the melting point of the coating material, the substrate temperature and the energy of the particles as they strike the substrate. Because of the generally higher particle energies in plasma-assisted processes, under comparable coating conditions lower substrate temperatures suffice than in the case of conventional evaporative coating. Especially with coating materials having higher melting points, compact films can be produced only if the particle energies are sufficiently high.
MAPPING OF p-STATE SYMMETRIC VERTEX MODEL ON THE HONEYCOMB LATTICE ONTO ITS ISING-SPIN COUNTERPART
Authors: ŠAMAJ L. , KOLESÍK M.
Published: November 2004

The mapping which produces a path between the p-state symmetric vertex model and the Ising model with spin [Formula: see text] on the honeycomb lattice is constructed. The mapping construction is based on a combination of decoration and gauge transformations. The formulation enables one to find the manifold in the vertex weights parameter space on which the mapping can be performed and to derive dual relations among the model parameters as well as the free energies of related symmetric vertex and Ising models. The extension of the mapping to arbitrary lattice coordination is outlined.
QUASI-CLASSICAL SELF-CONSISTENT THEORY OF ANHARMONIC CRYSTALS
Authors: ZUBOV V. I.
Published: November 2004

Using the unsymmetrized self-consistent field method the quasi-classical expansion of the one-particle density matrices is considered. The integral equations for the first quantum corrections to the classical one-particle probability densities are derived. The exact solution for the perfect crystals with the strong anharmonicity of the fourth order is found and used to calculate the first quantum correction to the effective amplitudes of the strongly anharmonic vibrations of atoms. The solution is obtained also for the semi-infinite linear chain as the simplest model of the anharmonic crystal with the surface.
STABLE hc/e VORTICES IN SUPERCONDUCTORS WITH SPIN-CHARGE SEPARATION
Authors: Sachdev Subir
Published: November 2004

A phenomenological model, F, of the superconducting phase of systems with spin-charge separation and antiferromagnetically induced pairing is studied. Above Hc1, magnetic flux can always pierce the superconductor in vortices with flux hc/2e, but regimes are found in which vortices with flux hc/e are preferred. Little-Park and other experiments, which examine periodicities with a varying magnetic field, always observe a period of hc/2e. The low energy properties of a symplectic large-N expansion of a model of the cuprate superconductors are argued to be well described by F. This analysis and some normal state properties of the cuprates suggest that hc/e vortices should be stable at the lowest dopings away from the insulating state at which superconductivity first occurs.
Lattice Effects in Flux Phases
Authors: Douçot B.
Published: November 2004

The uniform flux phases of the t-J model are studied using a slave boson representation. The gaussian fluctuations around the mean field saddle point are calculated. A key feature is the cancellation of Hall conductances of the spinons and the holons, in the limit of small doping. This cancellation leads to a pole in the global electromagnetic response function, in a mechanism which is very similar to anyon superconductivity.

Our main focus has been to evaluate the Hall conductance of the global system as a function of frequency and wave vector. Using various examples, we show that because of the cancellation of the two Hall conductances in the static and long wave-length limit, the behaviour of the global system is very sensitive to lattice effects. For instance, P. Wiegmann has found that the global Hall conductance vanishes in the static and long wave length limit, if one uses the response functions for the two dimensional continuous system.

However, a direct calculation of the response functions starting from the Hofstadter spectrum leads to a finite Hall conductance in the absence of an external field.

We show how this formalism can be used to calculate the local magnetic field which muons are expected to measure. The electric field of the muons induces a finite Hall current which in turn creates a finite magnetic field at the muon sites. Screening of the magnetic field by the Meissner effect has been taken into account and dielectric screening as well.

Preliminary results indicate that the predicted fields are approximately one order of magnitude larger than the upper bound from experimental results obtained by the Vancouver group.
COMPREHENSIVE MEAN FIELD THEORY FOR THE HUBBARD MODEL
Authors: JANIŠ V. , VOLLHARDT D.
Published: November 2004

We derive an exact expression for the grand potential of the Hubbard model in d=∞ dimensions. By simplifying the energy transfer between up and down spins we obtain a comprehensive mean-field theory for this model. It is (i) thermodynamically consistent in the entire range of input parameters, (ii) conserving and, (iii) exact in several non-trivial limits, e. g. in the free (U→0), atomic (t→0) and Heisenberg (U≫t, n=1) limit.
A RENORMALIZATION GROUP APPROACH FOR MANY-FERMION PROBLEMS
Authors: SHANKAR R.
Published: November 2004

A renormalization group transformation (RGT) that permits us to analyze the stability of fermionic systems to various perturbations in any number of dimensions is developed. An RGT that leaves invariant the free fermion system (on or off a lattiice) is defined and interactions are classified as relevent, irrelevent or marginal. It is shown how the RGT automatically considers competing instabilities simultaneously, in contrast to mean field theory, which focuses on just one. It is shown that at weak coupling only the BCS coupling is relevent unless there is nesting. Both Landau theory and the Kohn-Luttinger argument are discussed in this context.
Path Integral Study of Polaron Transport under High Electric Field
Authors: Su Z.B.
Published: November 2004

With help of the nonequilibrium Green’s function technique and the Feynman path integral theory, we present a self-consistent approach to the Thornber-Feynman model of a polaron under high electric field. The applied field and the electron-phonon interaction both are treated non-perturbatively so that the high-field effect as well as the quantum interference effect have been taken into account. A set of coupled equations are derived to consistently describe the drift motion and the fluctuation of the electron. By solving these equations numerically we obtain (1) the nonlinear relation between the drift velocity and the applied electric field; (2) the effective electron temperature, the nonequilibrium noise, and the distribution functions.
ON THE THEORY OF FIRST-ORDER PHASE TRANSITION IN ORDER-DISORDER FERROELECTRICS
Authors: WESSELINOWA J.M. , MARINOV M.S.
Published: November 2004

Based on the Hamiltonian of the Ising model in a transverse field, we have considered the four-spin interaction which is responsible for the first-order phase transition observed in order-disorder ferroelectrics. Using the method of the retarded Green’s function we have determined the relative polarization, the spin-wave energy, the transverse and longitudinal damping. They are numerically calculated and discussed for different temperature and tunneling frequency values in the cases of first- and second-order phase transitions.
IMPORTED CONFORMAL SYMMETRY OF ANYONS IN A UNIFORM MAGNETIC FIELD
Authors: AWAJI T. , HOTTA M.
Published: November 2004

We analyze an N-body quantum mechanics of anyons in an external magnetic field. It is pointed out that an SO(2, 1) dynamical symmetry, which is related to the conformal group, plays an important role in anyon dynamics. It is shown that the two-body spectrum is fully reproduced solely by the symmetry consideration. Moreover, we discuss some constraints on missing states from the symmetry consideration.
MONTE CARLO RENORMALIZATION GROUP STUDIES OF ANISOTROPIC BOND PERCOLATION
Authors: KIM C.S. , LEE MIN-HO
Published: November 2004

In complete analogy with thermal critical phenomena, it is expected that anisotropic percolation is in the same universality class as the isotropic one. However the previous result, obtained from the closed form conventional cell real space renormalization group method on the square lattice, the isotropic fixed point is completely unstable is known. We examine this in the large cell limit by using a Monte Carlo renormalization group method and show that the scaling exponent associated with anisotropy is not relevant.
NUMERICAL STUDY OF THE DISTRIBUTION OF PHASE AS AN ELECTRON MOVES IN A ONE-DIMENSIONAL, CONTINUOUSLY AND RANDOMLY VARYING POTENTIAL
Authors: MANNA SUSIL KUMAR , MOOKERJEE ABHIJIT
Published: November 2004

We study the phase distribution of the wavefunction of an electron as it moves through a one-dimensional, continuously and randomly varying potential. We note that in the mesoscopic region where the reflectance fluctuates and depends crucially on the boundary conditions, the phase distribution is always peaked and non-stationary. However, in the asymptotic region, which depends on the degree of disorder, for weak disorders, the phase distribution becomes uniform. However, for strong disorders, the phase distribution becomes stationary and peaked. This leads to phase pinning.
SOLVABLE CASES OF THE GENERAL SPIN-ONE ISING MODEL ON THE HONEYCOMB LATTICE
Authors: KOLESÍK M. , ŠAMAJ L.
Published: November 2004

We consider a general spin-1 Ising model on the honeycomb lattice and propose a systematic method for obtaining its solvable cases. The method is based on a sequence of transformations which produces a path between the spin-1 and spin-½ Ising models. Considering necessary conditions for performing the transformations and the solvability of the resulting spin-½ system, we recover the known and find some new nontrivial ‘exactly solvable’ subspaces in the parameter space of the spin-1 Ising model.
TWO-MODE GAUSSIAN DENSITY MATRICES AND SQUEEZING OF PHOTONS
Authors: TUCCI ROBERT R.
Published: November 2004

In this paper, we generalize to 2-mode states the 1-mode state results obtained in a previous paper. We study 2-mode Gaussian density matrices (i.e., density matrices of the form: exponential of a quadratic polynomial in the creation and annihilation operators for the two modes). We find a linear transformation which maps the two annihilation operators, one for each mode, into two new annihilation operators that are uncorrelated and unsqueezed. This allows us to express the density matrix as a product of two 1mode density matrices. We find general conditions under which 2-mode Gaussian density matrices become pure states. Possible pure states include the 2-mode squeezed pure states commonly mentioned in the literature, plus other pure states never mentioned before. We discuss the entropy and thermodynamic laws (Second Law, Fundamental Equation, and Gibbs-Duhem Equation) for the 2-mode states being considered. We study the change in entropy that is produced when a 2-mode Gaussian state is subjected to a measurement of the complex amplitude of one of its two modes. We derive upper and lower bounds for the final (i.e., after the measurement) entropy of the unmeasured mode, and we give necessary and sufficient conditions for the achievement of these bounds. The existence of the bounds is shown to be a consequence of the concavity property of the entropy function.
THE MULTIVARIABLE ALEXANDER POLYNOMIAL AND MODERN KNOT THEORY
Authors: SALEUR H.
Published: November 2004

This note is a summary of several recent works (by the author and collaborators) that study the Conway-Alexander link invariant in the light of quantum groups and topological quantum field theories. Their purpose is to understand connections between “modern” knot theory and more classical topological concepts.
THE DIFFEOMORPHISM GROUP APPROACH TO NONLINEAR QUANTUM SYSTEMS
Authors: GOLDIN GERALD A.
Published: November 2004

Unitary representations of diffeomorphism groups predict some unusual possibilities in quantum theory, including non-standard statistics and certain nonlinear effects. Many of the fundamental physical properties of “anyons” were first derived from their study by R. Menikoff, D.H. Sharp, and the author. This paper surveys new applications in two other domains: first (with Menikoff and Sharp) some surprising conclusions about the nature of quantum vortex configurations in ideal, incompressible fluids; second (with H.-D. Doebner) a natural description of dissipative quantum mechanics by means of a nonlinear Schrödinger equation different from the sort usually studied. Our equation follows from including a diffusion current in the equation of continuity.
CHERN-SIMONS EFFECTIVE ACTION FOR NON-RELATIVISTIC PLANAR ELECTRONS
Authors: DIAMANTINI MARIA CRISTINA , LINK ROBERT , SODANO PASQUALE
Published: November 2004

We investigate the low energy second quantized theory of non-relativistic planar electrons in external magnetic fields. We show that a U(1) Chern-Simons term appears in the effective action, for both the continuum and the lattice theories, as a result of a nontrivial phase holonomy. We also show, using the Jordan-Wigner transformation for planar spin systems, that the quantum frustrated XY model is described by an electron hopping model coupled to a U(1) Chern-Simons gauge field.
SELF-ENERGIES, RENORMALIZATION FACTOR, LUTTINGER SUM RULE AND QUASIPARTICLE STRUCTURE OF THE HUBBARD SYSTEMS
Authors: LÓPEZ-AGUILAR F. , COSTA-QUINTANA J.
Published: November 2004

In this paper, we give a method for obtaining the renormalized electronic structure of the Hubbard systems. The first step is the determination of the self-energy beyond the Hartree-Fock approximation. This self-energy is constructed from several dielectric response functions. The second step is the determination of the quasiparticle band structure calculation which is performed from an appropriate modification of the augmented plane wave method. The third step consists in the determination of the renormalized density of states deduced from the spectral functions. The analysis of the renormalized density of states of the strongly correlated systems leads to the conclusion that there exist three types of resonances in their electronic structures, the lower energy resonances (LER), the middle energy resonances (MER) and the upper energy resonances (UER). In addition, we analyze the conditions for which the Luttinger theorem is satisfied. All of these questions are determined in a characteristic example which allows to test the theoretical method.
SURFACE EFFECTS ON THE PHASE TRANSITIONS
Authors: BARBERO G. , BEICA T. , MOLDOVAN R. , STEPANESCU A.
Published: November 2004

The influence of the surface on the phase transitions is discussed. Classical models are reviewed and critically analyzed. Starting with a multilayer model, a new form of the surface energy is proposed. Our model predicts, contrary to previous models, a surface order parameter different from zero in a temperature range above the critical temperature characterizing the bulk phase transition. The application of the model to the evaluation of the surface tension gives results in agreement with experimental data.
MAGNETIC PROPERTIES OF THE DILUTED MAGNETIC SEMICONDUCTORS Zn1−xCoxSe and Zn1−xCoxS
Authors: MU YAOMING , ZHU JING-BING , LIU PU-LIN , PENG JIAN-PING , SHEN XUE-CHU
Published: November 2004

The magnetic specific heat, magnetization and low-field magnetic susceptibility of Co-based diluted magnetic semiconductors Zn 1−x Co x Se and Zn 1−x Co x S have been calculated by using a Hamiltonian which takes into account both the Heisenberg-type nearest-neighbor exchange interactions and spin-orbit interactions. A fair agreement between theory and experiment is obtained. No magnetization steps are predicted in the ranges of temperature and magnetic field considered here.
TAXONOMY OF THE SIXTEEN-VERTEX MODELS
Authors: BOUKRAA S. , MAILLARD J.-M.
Published: November 2004

A classification of the subcases of the sixteen-vertex model compatible with the infinite symmetry group generated by the inversion relations of the model is performed. The elliptic parameterization of these models is recalled, emphasizing the subvarieties of the parameter space for which this parameterization degenerates into a rational one. This situation corresponds to the vanishing of some discriminant and is deeply related to the critical and disorder manifolds for these models. We concentrate on subcases of the sixteen-vertex model for which factorizations of this discriminant occur, allowing further exact calculations.
THE STRENGTH OF ELECTRORHEOLOGICAL (ER) FLUIDS
Authors: CONRAD H. , CHEN Y. , SPRECHER A. F.
Published: November 2004

The definition of the strength of an ER fluid is discussed. Studies on the electrorheology of ER fluids containing zeolite particles in various oils indicate that the order of magntiude difference between the measured values of the yield stress and those calculated based on the axial force of interaction between particles in a single-row chain can be explained by an enhancement of the force due to the observed clustering of particles into multi-row chains. The force enhancement factor varied with the shear rate and the concentration of particles, but was relatively independent of the electric field, temperature and host fluid. Reasonable agreement existed between the predicted and the measured shear stress-shear strain curves and the concentration dependence of the yield stress when the appropriate force enhancement factor was taken into account. The present theoretical-experimental considerations suggest that ER fluids may attain a yield strength of ~ 50 kPa .
MACROSCOPIC BEHAVIOR OF ELECTRORHEOLOGICAL FLUIDS: TECHNIQUES FOR MEASURING RESPONSE TIME
Authors: WEISS KEITH D. , CARLSON J. DAVID
Published: November 2004

Two experimental methods, a dielectric spectroscopic technique and a channel flow technique, have been found to provide reasonable estimates of an ER fluid's response time. The dielectric data obtained for an ER fluid was adequately modeled using a well established Cole-Cole relationship for a symmetric distribution of relaxation times. A calculation of the particle's conductivity in the ER fluid also was found to be possible using the measured dielectric data. The response time obtained with the channel flow technique was in good agreement with the measured response time of a working ER fluid device.
TESTING ON A HIGH SPEED ELECTRO-RHEOLOGICAL CLUTCH
Authors: JOHNSON A. R. , BULLOUGH W. A. , FIROOZIAN R. , HOSSEINI-SIANAKI A. , MAKIN J. , XIAO S.
Published: November 2004

The design of a prototype ER clutch and its associated test facility have been described and sample results from the initial test programme are presented. The ER clutch shows considerable promise and outperforms various magnetic devices. Further clutch and ER fluid developments should increase these advantages.

The test facility described provides a quick method for obtaining a wide range of important fluid properties from a single small quantity of fluid in a single test facility operating under realistic engineering conditions. The results reported emphasize the need for continuing ER fluid development to increase the ER shear stress, to reduce the viscosity of the ER fluid, to reduce the electronic to ER shear stress time delay, and to improve the durability of ER fluids.
THEORETICAL STUDY OF LATTICE DYNAMICAL PROPERTIES IN FERROELECTRIC LiTaO3
Authors: JIANG YIMIN , GOU CHENG
Published: November 2004

We present the phonon-dispersion curves, the one-phonon density of states, the lattice specific heat cv(T) and the Debye temperature Θ(T) of the ferroelectric LiTaO 3, based on full lattice dynamical model whose parametèrs are fitted to the optical data and neutron measured dispersion curves. A model theory is developed to describe the transition from Debye to non-Debye behaviors observed in the low temperature part of the cv/T3 curve. The cv/T3 function, when is properly scaled, can be fitted by a general function derived from the model. It can be characterized by the temperature T max at which it has maximum, its maximum value (cv/T3)T=T max and its value at zero temperature (cv/T3)T=0. These results are considered useful in searching possibly anomalous phonon behavior from the specific heat cv(T).
ALLOY ANALOG APPROACH AND THE GUTZWILLER APPROXIMATION AS PARTICULAR CASES OF A MEAN-FIELD THEORY
Authors: ALIGIA A.A. , AVIGNON M.
Published: November 2004

We develop a new mean field-theory for systems with on-site correlations, like the Hubbard and Anderson models. It consists in a generalization of the saddle-point approximation to the functional integral representation proposed by Kotliar and Ruckenstein to more than one saddle point. It contains also the alloy analog approximation proposed by Hubbard as a particular case. For a half-filled Hubbard model and a model density of states appropriate for three dimensions, we obtain a metal to insulator transition as U increases. The effective Hamiltonian for the insulating phase contains two split bands (rather than only one with an extremely heavy mass) which reproduce correctly the Green’s functions of the atomic limit.
DEFORMATIONS OF DYNAMICS ASSOCIATED TO THE CHIRAL POTTS MODEL
Authors: BELLON M.P. , MAILLARD J-M. , ROLLET G. , VIALLET C-M.
Published: November 2004

We describe deformations of non-linear (birational) representations of discrete groups generated by involutions, having their origin in the theory of the symmetric five-state Potts model. One of the deformation parameters can be seen as the number q of states of a chiral Potts models. This analogy becomes exact when q is a Fermat number. We analyze the stability of the corresponding dynamics, with a particular attention to orbits of finite order.
HYDROGENATION OF CARBON CLUSTERS
Authors: Allaf A.W. , Hallett R.A. , Balm S.P. , Kroto H.W.
Published: November 2004

Carbon clusters are produced by laser vaporisation of the surface of a rotating/translating graphite disc into a high density pulse of helium. The present study illustrates the effects of mixing varying amounts of hydrogen into the helium carrier gas on the carbon nucleation products with particular reference to the behaviour of the small to medium sized clusters ranging from C 10– C 40 with the aim of verifying the existence of small fullerenes (even clusters, C n, 20<n<32).
MAGNETIC PROPERITES OF IRON CLUSTERS IN A MOLECULAR BEAM
Authors: de Heer Walt A. , Becker Jörg A. , Billas Isabelle M.L. , Milani Paolo , Châtelain A.
Published: November 2004

Magnetic properties of small iron clusters in a molecular beam are investigated by examining their deflections in a Stern-Gerlach magnet. The magnetization is probed as function of magnetic field, temperature and cluster size. The clusters are either heated with light from a pulsed laser which affects the vibrational temperature, or cooled in supersonic expansions which primarily affect the rotational temperature. We find that at temperatures up to 1500 K the magnetic moments of laser heated Fe 120–140 clusters are much larger than predicted either in the Heisenberg model or compared with the bulk values suggesting a stronger exchange interaction. Furthermore, rotationally cold clusters show anomalously magnetization which is non-linear with the applied field. This effect is found to be related to the anisotropy coupling of the total spin with the cluster framework. A model taking this effect into account and assuming a resonant coupling between the rotations and the Larmor precession of the spins gives good qualitative agreement with the observations.
OPTICAL EMISSION FROM CARBON CLUSTERS IN A SUPERSONIC EXPANSION
Authors: Balm S.P. , Hallett R.A. , Allaf A.W. , Stace A.J. , Kroto H.W.
Published: November 2004

The optical emission from electronically excited carbon clusters in a supersonic expansion of a laser vaporisation molecular cluster beam experiment is probed using photography, carbon deposition pattern recording and low resolution optical spectroscopy. The observed intensity distributions are highly non-uniform and sensitive to experimental parameters. They have important consequences for the intensities of cluster beams extracted from these expansions.
CORRELATION EFFECTS IN SOLID C60
Authors: Lof R.W. , van Veenendaal M.A. , Koopmans B. , Heessels A. , Jonkman H.T. , Sawatzky G.A.
Published: November 2004

The bandgap of solid C 60 is found to be 2.3±0.1 eV . The on-site molecular C 60 Coulomb interaction (U) as determined from the KVV C 60 Auger spectrum is found to be 1.6 ±.2 eV . This value of U is shown to be consistent with Frenkel type molecular excitons in the 1.5–2 eV range. These results lead us to suggest that doped C 60 should be considered as a highly correlated system with U/W comparable to that in high T c cuprates. The Auger spectroscpoy results are consistent with a rather long range Coulomb interaction on a single bucky ball indicating that a Hubbard model is not suitable to describe the electronic structure of a C 60 molecule.
MAGNETIC RESONANCE INVESTIGATION OF THE MAGNETIC TRANSITION IN TDAE-C60
Authors: Venturini P. , Mihailović D. , Blinc R. , Cevc P. , Dolinšek J. , Abramič D. , Zalar B. , Oshio H. , Allemand P.M. , Hirsch A. , Wudl F.
Published: November 2004

The ESR and NMR lines in powder samples of TDAE- C 60 do not show the expected frequency shifts due to long range ordering in the low temperature magnetic phase, but instead show only a relatively small line broadening below Tc=16 K. The temperature dependence of the lineshapes in ESR, the absence of a spontaneous magnetization as well as other magnetic properties suggest that the magnetic ordering below Tc=16 K is local and random, i.e. spin-glass like, rather than ferromagnetic. The possible finite-particle-size effects and possible microscopic mechanisms for the observed magnetic behavior are discussed.
THERMOMECHANICAL PROPERTIES OF CERTAIN ELEMENTAL CRYSTALS
Authors: RAHMAN S. M. MUJIBUR , SALEK SAMIRA
Published: November 2004

We have investigated the temperature variation of the Einstein temperatures and elastic constants of various metallic crystals. In this respect we have employed the interatomic pair potential involving pseudopotential and an appropriate exchange and correlation function. The temperature dependence of the properties concerned is taken into account through changes in the number densities. The systematic compilation of these thermomechanical properties may prove to be useful for various metallurgical purposes.
GAPLESS EDGE EXCITATIONS IN THE FRACTIONAL QUANTUM HALL EFFECT AND CONFORMAL INVARIANCE
Authors: BELOV A. A. , CHALTIKIAN K. D. , LOZOVIK YU. E.
Published: November 2004

We propose the conformal-invariant model for the description of the edge excitations (EE) in the FQH states using field-theoretical construction with current-current interactions. We discuss the classification of the topological orders (TO) of a given model. Using Chern-Simons ~ Wess-Zumino equivalence, we determine the possible types of the excitations in the FQHE — namely, we calculate their charges and statistics.
STUDY OF SUPERCONDUCTIVITY, STRUCTURE AND DOPANT SOLUBILITY IN Sm1−2xCaxPrxBa2Cu3O7−δ SYSTEM
Authors: WEN TING-LIAN , HÖRLIN TOM , NYGREN MATS
Published: November 2004

The superconductivity and crystalline structure of SmBa 2 Cu 3 O 7−δ doped both by Pr and Ca have been studied. T c decreases from 91.5 K to zero when doping concentration x in Sm 1−2x Pr x Ca x Cu 3 O 7−δ increases from zero to 0.4. Pr may have an effect of pair breaking in addition to hole-filling. It has been found that there is a solubility limit of about x=0.25 for Ca in orthorhomibic phase. The variation of crystalline parameters of orthorhombic 123 phase has been discussed in relation to valence state of Pr .
EXTRACTING LYAPUNOV EXPONENTS FROM SHORT TIME SERIES OF LOW PRECISION
Authors: ZENG X. , PIELKE R.A. , EYKHOLT R.
Published: November 2004

Different methods for computing the Lyapunov-exponent spectrum from a time series are reviewed. All algorithms are based on either Gram-Schmidt orthonormalization or Householder QR decomposition, and they use either the linearized map or a higher-order polynomial approximation. They also differ in implementation details. The ability to use these methods for a short time series of low precision is investigated, with special attention being given to the practicality of these algorithms; i.e., their efficiency and accuracy and the number of adjustable free parameters.
DETERMINATION OF PREFERRED STRUCTURE OF Bi-2212 CUPRATE BY THEORETICAL METHOD
Authors: WANG QIANG , HAN RUSHAN , YIN D.L. , GAN Z.Z.
Published: November 2004

Firstly, we calculated the Madelung site potentials and Madelung constants of Bi 2 Sr 2 CaCu 2 O 8 cuprate for two different structural models, i.e., (1) bismuth and oxygen on the same x-y plane, and, (2) on the different x-y plane, and indicated that the latter structural model is more stable. Furthermore, we proposed a modulation structural model for the Bi 2 Sr 2 CaCu 2 O 8.2 superconductor. These theoretical results explained some experimental observations.
NOISE INDUCED PHENOMENA IN ELECTRON PARAMAGNETIC RESONANCE SYSTEMS
Authors: GAMMAITONI L. , MARTINELLI M. , PARDI L. , SANTUCCI S.
Published: November 2004

Evidence of noise induced effects in electron-paramagnetic-resonance (EPR) experiments is reported. The phenomenon of Stochastic Resonance is presented and discussed as a cooperative effect between the noise and an external periodic driving, due to the bistable character of the EPR system.
MODEL OF THE LATTICE BOSON GAS: ρ-CONDENSATION
Authors: BOGOLUBOV N.N. , CORGINI M. , SANKOVICH D.P.
Published: November 2004

For the υ-dimensional lattice boson gas with the onsite repulsion and nearest neighbour sites attraction, we prove the existence of phase transition for ν≥3 and sufficiently large density when temperature is sufficiently small. This phase transition is connected with some type of Bose-Einstein condensation (ρ-condensation.4).
ANALYTIC RELATION BETWEEN THE PEAK TEMPERATURE OF THE IMAGINARY PART OF THE ac SUSCEPTIBILITY OF A SUPERCONDUCTOR AND THE APPLIED dc MAGNETIC FIELD
Authors: XINGLIN ZENG , LIEZHAO CAO , YUHENG ZHANG
Published: November 2004

The critical state model is employed to calculate the real (χ′) and imaginary parts (χ″) of ac susceptibility of a homogeneous superconducting slab (or a cylinder) under the conditions of ac magnetic field amplitude H ac ≪H dc (superimposed dc magnetic field) and low frequency. The calculated results are analytic and a relation (4π/c)J c (T p , H dc )d= (3/4) H ac between the χ″-peak temperature (T p ) and H dc is obtained. The theoretical prediction for χ′-χ″ curve is consistent with our experimental data, and the experimental power law [Formula: see text] in high-T c superconductors was explained using the above relation.
CRITICAL EXPONENTS AND CRITICAL SLOWING DOWN IN OPTICAL BISTABILITY — A PHENOMENOLOGICAL APPROACH
Authors: TSAO PEI-HSI , LIU WEI-CHIH
Published: November 2004

A phenomenological approach is adopted for investigating the critical behavior related to optical bistability (OB). This method is similar to Landau theory of critical phenomena and is applied to find the critical exponents and to analyze critical slowing down. It is shown in general that critical exponents for OB are classical ones and the relaxation time of critical slowing down varies with the external parameter p as (p − pc)−1/2 around the transition point p = pc.
OPTICAL ACTIVITY AND LIGHT SCATTERING IN HIGHLY CHIRAL LIQUID CRYSTALS
Authors: COLLINGS PETER J.
Published: November 2004

Theoretical and experimental optical activity and light scattering work in highly chiral liquid crystals is reviewed, starting from the early studies twenty years ago and ending with the most current investigations. Pretransitional effects in the isotropic and smectic A phases of highly chiral liquid crystals are discussed, as well as optical activity and light scattering effects in both the blue phases and smectic A * phase.
IN-SITU PREPARATION OF YBa2Cu3O7 SUPERCONDUCTING THIN FILMS BY PULSED Nd:YAG LASER DEPOSITION
Authors: SU QINGXIN , XU SHIFA , CUI DAFU , LU HUIBIN , TIAN YONGJUN , ZHANG YINGZI , ZHAO BAIRU , CHEN ZHENGHAO , LI LIN , YANG GUOZHEN
Published: November 2004

High-T c superconducting thin films of YBa 2 Cu 3 O 7 were grown in-situ on (100) SrTiO 3 substrates by Nedymium:yttrium aluminum garnet [Nd:YAG] laser ablation. The effects of the substrate temperature on the transition temperature, microcrystalline structure and surface morphology of the films were discussed. Best results were obtained in the 730°–770°C range. X-ray diffraction analysis showed that these films were highly c-oriented with the c-axis perpendicular to the substrate surface. At the optimum substrate temperature, a very smooth morphology with only a few small particles were observed by scanning electron microscopy. The zero resistance temperature of these films were ≥ 90 K with a narrow transition width and the ac susceptibility measurement also gave the same result. The highest critical current density obtained at 77 K and zero magnetic field was 3.8 × 106 A/cm 2.
MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS VII — ESR OF DPPH COATED ON A THIN BiSrCaCuO FILM FABRICATED ON MgO(100) SUBSTRATE
Authors: SUGAWARA K. , SUGIMOTO T. , SHIOHARA Y. , TANAKA S.
Published: November 2004

ESR of DPPH coated on a Bi-Sr-Ca-Cu-O (BSCCO) film (350 Å thick) fabricated on MgO(100) substrate by MOCVD was studied. Temperature dependence of the ESR peak-to-peak linewidth, ΔH pp , and the effect of applied magnetic field on ΔH pp have been studied below about 100 K. The results were compared with those of ESR of DPPH coated on ceramic Y-Ba-Cu-O samples (powder and bulk) made by the MPMG method. The DPPH ESR for the BSCCO film revealed that ΔH pp was independent of applied magnetic field up to about 9 kG. In addition, no similarity between the temperature dependence of the excess ESR linewidth of the DPPH and that of critical current density was found for the BSCCO film. These results for the BSCCO film are different from those for the MPMG YBCO samples.
SCREENING PROPERTIES OF HYDROGEN UNDER HIGH PRESSURE
Authors: GARAVELLI S. L. , OLIVEIRA F. A.
Published: November 2004

In this work we study screening in hydrogen at high pressure. We use a scaling approach to obtain the critical pressure for the atomic phase-molecular phase transition. Our results is in agreement with quantum Monte Carlo simulations.
IS THERE A DELOCALISATION TRANSITION IN A TWO-DIMENSIONAL MODEL FOR QUANTUM PERCOLATION?
Authors: DASGUPTA INDRA , SAHA TANUSRI , MOOKERJEE ABHIJIT , CHAKRABARTI B. K.
Published: November 2004

We estimate the transmittance of the quantum percolation model of Eggarter and Kirkpatrick (1972) on the square lattice of various sizes using the vector recursion method. We note from finite size scaling that there is no delocalisation transition for any degree of disorder in two dimensions.
THE PREPARATION AND CHARACTERIZATION OF SUPERCONDUCTING THIN FILMS IN A HOMOGENEOUS DISPERSION SYSTEM
Authors: ZHANG YULING , CHENG DESHU , CHEN ZONGQI , WONG GUAN XING , HAN ENSHEN , WU SHIYING , LI YUSHU , LIANG JINGKUI , CHEN XIAOLONG , XIE SISHEN
Published: November 2004

Superconducting thin films YBa 2 Cu 3 O 7−x of a large size and arbitrary shapes were synthesized in situ on (100) SrTiO 3 substrates by colloidal suspension deposition using a suspension consisting of monodispersed particles of Y 2 O 3, BaO and CuO of nanocrystalline 50 to 200 nm in size. The thicknesses of the superconducting films ranged from 2000 to 5000 Å. The orthorhombic to tetragonal phase transition in superconducting thin films YBa 2 Cu 3 O 7−x under different temperatures and durations in flowing oxygen was investigated by means of X-ray diffraction.
EFFECT OF JOSEPHSON MEDIUM UNDER TUNNELING IN BI-SR-CA-CU-O
Authors: SVISTUNOV V. M. , GRIGUT' O. V. , DYACHENKO A. I. , REVENKO YU. F.
Published: November 2004

Tunneling characteristics of high-T c oxide superconductor Bi-Sr-Ca-Cu-O have been measured in the wide bias voltage and temperature range. Near zero bias voltage tunneling conductivity σ (U) is expressed by the U1/2 at low temperature, which goes to the linear one at U > 100 mV . Background conductivity metaloxide is determined by Shottky barrier on surface high-T c . It has been found that the peaks of σ (U) curves for low-ohmic contacts are well described theoretical model of destruction of superconductivity of the intergranular weak links. Parameters of these links are estimated. Zero bias anomaly conductivity peaks are explained by breakdown weak links with small critical current.
FREDHOLM DETERMINANT REPRESENTATION OF QUANTUM CORRELATION FUNCTION FOR SINE-GORDON AT SPECIAL VALUE OF COUPLING CONSTANT
Authors: ITOYAMA H. , KOREPIN V. E. , THACKER H. B.
Published: November 2004

Correlation functions of the Sine-Gordon model (which is equivalent to the Massive-Thirring model) are considered at the free fermion point. We derive a determinant formula for local correlation functions of the Sine-Gordon model, starting from Bethe ansatz wave function. Kernel of integral operator is trigonometric version of the one for Impenetrable Bosons.
EXAFS STUDIES OF THE FERROELECTRIC PHASE TRANSITIONS INDUCED BY OFF-CENTER IONS IN PbSxTe1−x and ZnxCd1−xTe ALLOYS
Authors: WANG ZHIHAI , BUNKER BRUCE A. , MAYANOVIC ROBERT A. , DEBSKA URSULA , FURDYNA JACEK K. , ISLAM QUAZI
Published: November 2004

Using the Extended X-ray Absorption Fine Structure (EXAFS) technique, we have investigated the local structure of disordered PbSxTe1−x and ZnxCd1−xTe alloys at temperatures below and above the reported ferroelectric transition temperatures. For the PbSxTe1−x alloys (x=0.10, 0.18, and 0.30), the sulphur ions are found to be off-center in both the high and the low temperature phase and Pb sublattice and Te sublattice shift relative to one another below the transition temperature. For ZnxCd1−xTe alloys (x=0.10 and 0.20), the zinc ions are found in a slightly asymmetric site in the cages formed by four NN Te ions and no relative shift between the cation and anion sublattice is observed. We discuss our results concerning the ferroelectric phase transitions (FPT) induced by off-center ions in these two systems.
INFLUENCE OF SYNTHESISING ROUTES ON RESISTIVITY AND AGING CHARACTERISTICS OF Bi-CUPRATE SUPERCONDUCTORS
Authors: VIDYALAL V. , RAJASREE K. , VALLABHAN C.P.G.
Published: November 2004

Lead-doped Bi-2223 superconductors were prepared by two main popular solid state reaction routes, viz. solid state diffusion reaction and the matrix method. Even though both routes produce single-phase materials superconducting at 110 K, the resistivity behaviors above Tc are found to be different. Aging/degradation behavior was studied in terms of Tc on both sets of samples stored in a desiccator for eight months. Our studies indicate that the synthesising routes play a major role in the preparation of high quality bulk Pb-doped Bi-2223 superconductors which are more resistant to degradation when exposed to humid conditions.
GROUND-STATE ENERGY FOR 1D (t, U, X)-MODEL AT LOW DENSITIES
Authors: BUZATU F.D.
Published: November 2004

In describing the properties of quasi-1D materials with a highly-screened interelectronic potential, an attractive hopping term has to be added to the Hubbard Hamiltonian. The effective interaction and the ground-state energy in ladder approximation are analyzed. At low electronic densities; the attractive part of the interaction, initially smaller than the repulsive term, can become more effective, the ground-state energy decreasing below the unperturbed value.
GEOMETRIC PHASE SHIFTS IN DISSIPATIVE CLASSICAL SYSTEMS
Authors: KEPLER THOMAS B.
Published: November 2004

The reanalysis of the adiabatic theorem initiated by Berry and leading to the discovery of the unexpectedly elegant geometric phase shift, has been broadened in scope by many authors; most recently, to dissipative classical dynamical systems. I review this work with an emphasis on the fundamental characteristics underlying all instantiations of geometric phase shifts.
PHOTOELECTRON SPECTROSCOPIC STUDY OF κ-(BEDT-TTF)2Cu(NCS)2 ORGANIC SUPERCONDUCTOR
Authors: ITTI R. , MORI H. , IKEDA K. , HIRABAYASHI I. , KOSHIZUKA N. , TANAKA S.
Published: November 2004

Experimental evidence for understanding the transport and electrical properties of the 10.4 K organic superconductor κ-(BEDT-TTF)2Cu(NCS)2 (where BEDT-TTF represents bis(ethylenedithio)tetrathiafulvalene) has been achieved by X-ray and ultraviolet photoelectron spectroscopic (XPS and UPS) measurements. Chemical environment of the atoms in this organic superconductor is discussed based on the XPS core-level results. Binding energies of the inequivalent C and S sites in the cation BEDT-TTF and the anion Cu(NCS)2 are found to be different and an assignment is made. The valences of Cu and N were observed to be typically +1 and −3, respectively. The results indicate that bonding is somewhat covalent in the BEDT-TTF while it is ionic in the Cu(NCS)2, i.e., conduction in this compound occurs essentially on the two-dimensional network of the BEDT-TTF molecules. Measurements of the valence band region revealed a broad valence band structure with several peak features.
SEQUENTIAL VERSUS COHERENT TUNNELING MECHANISMS DISTINGUISHED IN I-V CHARACTERISTICS
Authors: CHEN L.Y. , TING C.S.
Published: November 2004

The I–V characteristics of a 3D double-barrier resonant-tunneling structure is investigated to demonstrate the differences between coherent and sequential tunneling mechanisms. Increasing the ratio of phase-breaking scattering rate over tunneling broadening width from 0 to ∞, tunneling transport goes from the coherent to the sequential limit. In the first resonance region, I–V curve does not distinguish these two processes. In the second and higher resonance regimes, however, sequential tunneling current becomes appreciably larger than its coherent counterpart.
SECOND-ORDER DYNAMICS IN THE COLLECTIVE EVOLUTION OF COUPLED MAPS AND AUTOMATA
Authors: BINDER PHILIPPE-MICHEL , PRIVMAN VLADIMIR
Published: November 2004

We review recent numerical studies and the phenomenology of spatially synchronized collective states in many-body dynamical systems. These states exhibit thermodynamic noise superimposed on the collective, quasiperiodic order parameter evolution with typically one basic irrational frequency. We concentrate on the description of the global temporal properties in terms of second-order difference equations.
MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS VIII — ESR OF DPPH COATED ON BiSrCaCuO FILMS FABRICATED ON MgO (100) SUBSTRATES
Authors: SUGAWARA K. , TANAKA S.
Published: November 2004

ESR of DPPH coated on Bi - Sr - Ca - Cu - O films fabricated on MgO (100) substrates by MOCVD have been studied for samples with different thicknesses, 1000 Å and 100 Å. Temperature dependence of the ESR peak-to-peak linewidth, ΔH pp , revealed that ΔH pp , increases with film thickness. The excess ESR linewidth, δ (ΔH pp ) was also analyzed in terms of (1-t)α, with t=T/T c , giving for example α=4±1 for the 1000 Å thick sample. The ESR lineshapes were distorted by rotating the samples in applied magnetic fields. Severe distortion was found for the 1000 Å sample below about 30 K, but the distortion almost disappears at temperatures above 30 K. The applied magnetic field effects were also examined in both field-cooled and zero-field-cooled cases.
TIME DEVELOPMENT OF FLUORESCENCE SPECTRA OF A THREE-LEVEL ATOM IN A SQUEEZED VACUUM
Authors: JAYARAO ARUNDHATI S. , LAWANDE SURESH V. , D'SOUZA RICHARD
Published: November 2004

We present an analytical study of the time-dependent spectra of a three-level atom in the cascade configuration driven by two intense coherent fields and damped by a broadband squeezed vacuum. We have also studied the influence of the initial state preparation of the atom on the transient spectrum.
CURRENT–VOLTAGE CHARACTERISTICS OF BARIUM POLYMETHACRYLATE
Authors: CHOHAN M. H. , ZULFIQAR M. , SAPRA Z. H. , HUSSAIN RIZWAN , ZULFIQAR S.
Published: November 2004

Current–voltage characteristics of Barium Polymethacrylate (BaPMA) in the form of Al-BaPMA-Al structures have been studied. The currents are measured in the voltage range 10 V–1 kV. At low voltages an ohmic relation is observed and at higher voltages the Poole-Frenkel mechanism is proposed. The mechanism of conduction has been explained on the basis of different current-voltage and current-temperature curves. The activation energy values calculated using Arrhenius relation fall in the range 0.25–2 eV, suggesting a sequence of trapping levels.
TEMPORAL DEVELOPMENT OF NONLINEAR BLOCH ELECTRON MINIBAND TRANSPORT
Authors: LEI X. L. , HORING N. J. M. , CUI H. L.
Published: November 2004

We present a balance-equation calculation of the transient response of Bloch electron transport in a superlattice miniband to an external time-dependent electric field parallel to the growth axis. Upon turning on a step electric field having strength within the range of negative differential mobility in the steady-state velocity-field curve, the drift velocity exhibits very pronounced overshoot. Immediately after the drift velocity reaches its maximum, the instantaneous inverse effective mass may fall within the range of negative values in consequence of the driving field. The rise of the electron temperature, however, is much slower, such that the behavior of the velocity response to an impulsive electric field is markedly dependent on the duration of the impulse.
LATTICE-DYNAMICS STUDY OF K3C60
Authors: BELOSLUDOV V. R. , SHPAKOV V. P.
Published: November 2004

A model for K 3 C 60 taking into account coulombic interaction between K + and [Formula: see text], covalent bonds in C 60, and the Van der Waals interaction between C 60 molecules is presented. Vibrational spectrum is calculated using the model, and a behavior of the dispersion curves for different types of vibrations is investigated.
NEURAL NETWORKS FOR THE RECOGNITION OF ENGRAVED MUSICAL SCORES
Authors: MARTIN PHILIPPE , BELLISSANT CAMILLE
Published: November 2004

The image analysis levels of a recognition system for engraved musical scores are described. Recognizing musical score images requires an accurate segmentation stage to isolate symbols from staff lines. This symbols/staves segregation is achieved by the use of inscribed line (chord) information. This information, processed by a multilayer perceptron, allows an efficient segmentation in terms of the remaining connected components. Some of these components are then classified, using another network, according to a coding of their skeleton graph. Special attention is paid to the design of the networks: the architectures are adapted to the specificities of each task. Multilayer perceptrons are employed here together with other more classical image analysis techniques which are also presented.