bluuebunny/crossref_metadata_2025 huggingface dataset:
ON THE RANDOM QFT FOUNDATIONS OF STATISTICAL MECHANICS
Authors: SYROS C.
Published: November 2004

The Statistical Mechanics of the N-particle system is derived from Quantum Random Field Theory. An asymptotically measure preserving, flow operator has been obtained from the QFT evolution operator. A basic assumption is that the field Lagrangian is a generalized, infinitely divisible random field, and the interaction Hamiltonian varies in time in a step-wise manner at the transition lattice space-time points. Macroscopic boundary conditions are imposed on the wave functions. The density matrix, the partition function, the Bose-Einstein, the Fermi-Dirac distributions and the thermodynamic temperature follow. The equilibrium or non-equilibrium temperature have been obtained as functionals of the interaction Hamiltonian. The chemical potential has also been derived from the theory.
SECOND ORDER HIGH DENSITY EXPANSION FOR FREE ENERGY AND ORDER PARAMETER
Authors: BARTKOWIAK M. , CHAO K.A.
Published: November 2004

The self-consistently renormalized high-density expansion (SHDE) is first used to determine temperature dependence of order parameter. Free energy and magnetization of the Ising model has been calculated to the second order. It is shown that the unphysical discontinuity of the order parameter as a function of temperature, which appears in the first-order approximation, still remains in the second-order calculation.

Based on the 1/d expansion, we then construct a method to select (1/z)i contributions from the high density expansion terms. This method is applied to the first and second-order self-consistent equation for magnetization. Selection of the first order in 1/z contributions within the first order of the SHDE leads to considerable improvement of the behavior of magnetization as a function of temperature, and application of the local approximation to the second order of the SHDE term gives an acceptable single-value behavior of the order parameter.
EFFECTIVE KINETIC THEORY OF COMPLEX CHEMICAL REACTION SYSTEMS AND THERMODYNAMICS: GENERAL THEORY OF THE FORWARD AND REVERSE REACTION RATES
Authors: SUZUKI MASUO , INOUE HAKUAI
Published: November 2004

In this paper a new precise definition of the forward and reverse reaction rates of complex reaction processes is proposed. To apply the definition to reaction systems a general branching law, which yields the recursion formula on the forward and reverse reaction rates, is derived and general rate expressions are presented for complex reaction systems in the steady state. Based on these newly defined reaction rates, the thermodynamic relation between reaction rates and the affinity holds in chemical reaction processes of any order.
RENORMALIZATION-GROUP STUDY OF SELF-AVOIDING WALKS BY USING THE CENTER-RULE WEIGHT FUNCTIONS
Authors: LEE FELIX , CHEN H.H.
Published: November 2004

Based on the center-rule weight functions, the renormalization-group technique has been applied to study critical properties of the self-avoiding walks on the square lattice. The exact weight functions previously obtained for cells of sizes b≤4, are extended to b≤8 by machine computations. Renormalization-group analyses of these weight functions give the critical fugacity Kc=0.37905 and the critical exponent v=0.7507±0.0037.
ON THE ROW-CONVEX POLYGON GENERATING FUNCTION FOR THE CHECKERBOARD LATTICE
Authors: LIN K.Y. , TZENG W.J.
Published: November 2004

Exact solution for the most general four-variable generating function of the number of row-convex polygons on the checkerboard lattice is derived. Previous results for the square lattice, rectangular lattice, and honeycomb latticc are special cases of our solution.
OPTICAL PROPERTIES OF CUPRATE SUPERCONDUCTORS INFLUENCED BY A MAGNETIC FIELD
Authors: WEBER H. J.
Published: November 2004

Reflection measurements on a one-domain single crystal of YBa 2 Cu 3 O 7-δ and transmission measurements on single crystals of Bi 2 Sr 2 CaCu 2 O 8 show a state of spontaneously broken symmetry below certain transition temperatures T s somewhat above the respective superconduction temperature T c . In both materials the sign of the effect can be controlled by an external magnetic field. In transmission measurements on films of YBa 2 Cu 3 O 7-δ near T s a remanent circular dichroism is observed after applying an external magnetic field. Furthermore, the films show a Curie-Weiss type increase of magnetic circular dichroism near T s . The magnetic field effects are considered as evidence for a state with broken time reversal symmetry below T s .
SOLITONS IN CHERN–SIMONS/ANYON SYSTEMS
Authors: Jackiw R.
Published: November 2004

The recently discovered solitons in Chern–Simons/anyon systems me reviewed.
TOPOLOGICAL ORDERS AND CHERN-SIMONS THEORY IN STRONGLY CORRELATED QUANTUM LIQUID
Authors: WEN XIAO-GANG
Published: November 2004

We review the topological orders in strongly correlated quantum liquids. The characterization of the topological orders through ground state degeneracy, non-Abelian Berry's phases and edge excitations are discussed.
THE EXACT ANYON SPECTRA AND FRACTIONAL STATISTICS
Authors: Chou Chihong
Published: November 2004

We seek the analytic eigenstates for an N-identical anyons in an external harmonic oscillator potential.
Incompressible Quantum Fluids of Ideal Anyons in a Strong Magnetic Field
Authors: Zhang F. C. , Ma M.
Published: November 2004

Ideal anyons with statistics ν in a strong magnetic field are studied by means of a similarity transformation. The ground state exhibits "integer" quantum Hall effect at filling factor 1/ν with quasiparticle excitations of charge q/ν and statistics -1/ν. Certain electron FQH states can be considered as realization of this, for example, the sequence 2/5, 3/7, … hierarchy of the 1/3 state. This may explain the observed quasiparticle-quasihole asymmetry in the fractional quantum Hall hierarchy.
Induced Topological Terms, Hidden Local Symmetry, and Anyon Superconductivity
Authors: Ho C.-L. , Hu B. , Yu H. L.
Published: November 2004

We show how the topological Chern-Simons term in three dimensions and the θ-term, [Formula: see text] in four dimensions can be dynamically generated due to quantum fluctuations in Nambu-Jona-Lasinio models. These results give a vivid demonstration of hidden local symmetry at work. The fluctuation-induced Chern-Simons term provides a natural way to incorporate fractional statistics and thus a more direct connection with anyon superconductivity. Possible phenomenological implications of this approach in particle physics are also discussed.
ZERO-BIAS ANOMALIES IN THE CURRENT-VOLTAGE AND CONDUCTANCE-VOLTAGE CHARACTERISTICS OF HIGH-CRITICAL-TEMPERATURE SUPERCONDUCTOR JUNCTIONS
Authors: WALSH THOMAS
Published: November 2004

The occurrence of zero-bias anomalies (ZBAs) in the current-voltage and conductance-voltage characteristics of high-critical-temperature superconductors (HTS) is reviewed. Following a historical introduction, we summarize studies noting HTS ZBAs. Several explanations of the ZBAs in HTS tunneling characteristics have been proposed including a resistance in series with a Josephson junction, a conductive channel near the Fermi energy ε F , localized magnetic states on film surfaces, proximity effects, a peak in the electron density of states near ε F , an array of junctions in an HTS ceramic sample, coupling between a film's normal surface layer and the superconducting layer below the surface, quasiparticle tunneling, and phase diffusion. The plausibility and implications of these suggested explanations are discussed. Experiments to answer questions that remain regarding the source and significance of the ZBAs are proposed.
Strongly Correlated Fermi Liquid and the Normal State of High Tc Superconductors
Authors: Wang Ziqiang
Published: November 2004

New insights into the strongly correlated Fermi liquid state of the SU(N) infinite-U Hubbard and t-J models are presented in connection to the metallic state of unbroken symmetry of the copper oxide planes. The nature of single particle and collective excitations is analyzed and the Landau Fermi Liquid parameters are derived. The one-particle spectral function in the Hubbard valence band is obtained with both Hubbard and Gutzwiller-like features. A simple interpretation of the large incoherent background is given in terms of a superposition of quasiparticles and a collective mode describing the propagation of a bare hole in a large U system. The spin exchange interactions produce very low lying collective modes describing the propagation of staggered spin chirality which soften at incommensurate wavevectors. The quasiparticles are strongly scattered by the low lying chirality fluctuations resulting in deviations from canonical Fermi liquid behavior at low energy scales. Of the same origin, the quasiparticle self energy is found to be strongly k-dependent. It leads to corrections to the dispersion and enhancement of the quasiparticle lifetime in the hole-like region of the interacting Fermi surface. The combined effects are sufficient to produce a sign change in the Hall coefficient evaluated for parameters relevant to the copper oxide planes. We show that these models also exhibit a zero temperature fluctuation driven transition from Fermi liquid to non Fermi liquid phase without the onset of magnetic ordering below a critical doping δc=1/4N, whereby providing a microscopic mechanism for the destruction of the Fermi liquid coherence by strong longitudinal gauge fluctuations which represent the effects of the infinite-U constraint.
Spin-Charge coupling in doped Mott Insulators
Authors: Wheatley J.M. , Schofield A.J.
Published: November 2004

The coupling of charge to spin degrees of freedom in two dimensional doped Mott insulators is briefly reviewed. The problem of the long-wavelength charge response is mapped to the response of a Bose system coupled to a fictitious electromagnetic field. We describe an approach to the conductivity and diamagnetic response in this model.
ABSORPTION SPECTROSCOPY OF ELECTRONIC STATES NEAR FERMI LEVEL: TEMPERATURE CHANGES OF SUPERCONDUCTING YBa2Cu3O7−δ FILMS AT Tc
Authors: FUGOL I. YA. , SAMOVAROV V.N. , RYBALKO YU. I. , ZHURAVLEV V.M.
Published: November 2004

The temperature behavior of the absorption spectra of superconducting YBa 2Cu3O7−δ textured films is measured in a 1.5÷3.0 eV energy region with varying temperatures from 25 to 300 K. The spectra are found to be sensitive to a superconducting transition: the temperature-dependent behaviour of absorption at T>Tc undergoes critical changes under the superconducting transition and for T<Tc the spectrum ceases to depend on temperature. The spectra display an exciton maximum in the optical gap Eg=1.95 eV. The spectrum freezing at T<Tc can be explained assuming that the Fermi level is in temperature resonance with a narrow local level which is responsible for a delta-like singularity in the density of states.
THE SOLUTION OF THE THREE-DIMENSIONAL TWISTED GROUP LATTICES
Authors: SAMUEL STUART
Published: November 2004

We define new lattices called d-dimensional twisted group lattices. They are similar to ordinary lattices except that abstract screw dislocations are present at the centers of all plaquettes. Some physical aspects are enumerated. We consider the statistical mechanics system of free propagation on the three-dimensional twisted group lattice. For this case, the partition function is explicitly computed by finding the irreducible group representations.
INTERFACE EQUATION AND VISCOSITY CONTRAST IN HELE-SHAW FLOW
Authors: CASADEMUNT J. , JASNOW DAVID , HERNÁNDEZ-MACHADO A.
Published: November 2004

We derive an integro-differential equation for the evolution of the interface separating two immiscible viscous fluids in a Hele-Shaw cell with a channel geometry, for arbitrary viscosity contrast. Our equation differs from a previous one obtained by a vortex-sheet formulation of the problem, in that the normal component of the interface velocity is formally decoupled from the gauge-dependent tangential part. The result is thus a closed integral equation for the normal velocity. We briefly comment on the advantages of such a formulation and implement an alternative computational algorithm based on it. Preliminary numerical results confirm a highly inefficient finger competition in the zero viscosity contrast limit.
THEORY OF THE EDGE STATES IN FRACTIONAL QUANTUM HALL EFFECTS
Authors: WEN XIAO-GANG
Published: November 2004

The dynamical theory of the edge excitations of generic fractional quantum Hall (FQH) states is summarized and expanded. The low energy effective theory of the edge excitations for the most general abelian FQH states (including spin-unpolarized and multi-layer FQH states) and some non-abelian FQH states is derived using several different methods. The propagators of the electrons and the quasiparticles are calculated for the above FQH states. The microscopic theory of the edge excitations for the Laughlin states is also presented. Some simple applications of the edge theory to the transport properties of the FQH states are discussed. In particular, the tunneling between edge states is shown to be a powerful tool to probe the internal topological orders in the FQH states. It can be used to distinguish different FQH states with the same filling fraction and to detect the non-abelian FQH states in experiments.
DISCRETE QUANTUM GRAVITY: THE REGGE CALCULUS APPROACH
Authors: WILLIAMS RUTH M.
Published: November 2004

After a brief introduction to Regge calculus, some examples of its application in quantum gravity are described. In particular, the earliest such application, by Ponzano and Regge, is discussed in some detail and it is shown how this leads naturally to current work on invariants of three-manifolds.
NON-LINEAR WKB ANALYSIS OF THE STRING EQUATION
Authors: FUCITO F. , GAMBA A. , MARTELLINI M. , RAGNISCO O.
Published: November 2004

We apply non-linear WKB analysis to the study of the string equation. Even though the solutions obtained with this method are not exact, they approximate extremely well the true solutions, as we explicitly show using numerical simulations. “Physical” solutions are seen to be separatrices corresponding to degenerate Riemann surfaces. We obtain an analytic approximation in excellent agreement with the numerical solution found by Parisi et al. for the k=3 case.
GEOMETRY OF QUANTUM VORTICES AND LINK INVARIANTS
Authors: PENNA VITTORIO , SPERA MAURO
Published: November 2004

We report on recent and ongoing research in the context of the geometric approach to quantum vortices and link invariants (via the Marsden-Weinstein theory and Chen’s iterated path integrals).
THEORETICAL ASPECTS OF QUANTUM HALL EFFECT AND TWO-DIMENSIONAL CFT
Authors: CRISTOFANO G. , MAIELLA G. , MUSTO R. , NICODEMI F.
Published: November 2004

A review of the QHE is presented where the emphasis is placed on the role of the magnetic translation group and of the related topological properties. After a presentation of general experimental and theoretical features we briefly summarize known results of two-dimensional Conformal Field Theory relevant for the QHE. Then we show how to evaluate groundstate wave functions on the plane and on the torus by the use of CFT techniques. In the latter case it is shown how for filling ν=1/m a consistent description is achieved by means of a finite set of Coulomb Gas Vertex Operators. They describe (fractional) charged particles with the associated quantized magnetic flux (“anyons"). Furthermore, from these vertices and relative highest weight states, one does find that the g.s.w.f. for the torus should be m-fold degenerate showing, also, the role of a new kind of long-range topological order recently advocated. Then we show that the presence of m sectors of edge states for a cylinder is strictly related to such a degeneracy, and their relation with a Kac-Moody algebra is discussed.
PHENOMENOLOGICAL IMPLICATIONS OF HIGH-Tc SUPERCONDUCTIVITY
Authors: MA Y. L. , DAI X. X.
Published: November 2004

We develop a phenomenological model for high-T c superconductors. Some main features are emerging in copper oxides: characteristic quasi two-dimensional Cu-O planes, strong correlation of antiferromagnetism, existence of a vortex lattice structure, and observation of a small coherence length and a large penetration depth. These features indicate that the superconductive pair is reasonably constrained to a small volume in real space and may be conceived of as a string-carrying vortex, and therefore can be well simulated by the dual phenomenological local boson fields [Formula: see text] and Φ. The various mean-field ground states of the system are discussed. The field equations of motion are originally solved to get approximate analytical soliton solutions. The effective Hamiltonian is formulated by a variational method for finite temperatures. The model parameter behaviour described by the relationship of the variational parameters is investigated. We discuss the critical temperature T c , the specific heat cV and its jump Δc at T c , and the critical magnetic fields H c1 and H c2 . These results are in agreement with experimental observations, especially the critical behaviours and the zero temperature values. The model also allows interpretation of the variation of T c with oxygen vacancy x and that with doping fraction δ in Cu-O planes, as well as the dependence of γ (defined as the specific heat coefficient of the T-linear term) on δ.
CORRELATION FUNCTIONS OF THE TWO-STATE VERTEX MODEL ON THE CAYLEY TREE
Authors: KOLESÍK M.
Published: November 2004

The symmetric two-state vertex model on the Cayley tree is studied. Two types of first-order phase transitions are distinguished according to the behaviour of correlation functions in the high-temperature phase. A manifold in the model parameter space on which the correlations vanish is shown to be the same as for the honeycomb lattice.
ANYONIC SUPERCONDUCTIVITY WITH FERROMAGNETIC GROUND STATE
Authors: CHAKRABORTY B. , RAMASWAMY S. , RAVISHANKAR V.
Published: November 2004

We study a system of non-relativistic two-dimensional spin-1/2 fermions minimally coupled to Chern-Simons and Maxwell gauge fields, at zero temperature. A self-consistent mean field approach leads to a ferromagnetic ground state which nevertheless is also superconducting. We calculate the spin and current correlation functions and show that there is a Meissner effect for weak external magnetic fields, characterised by two penetration lengths. The dispersion relations for the two longitudinal excitations are given. Further, the system supports spin waves which are massless in the absence of electromagnetic fields.
STRUCTURE OF s-p BONDED METAL CLUSTERS WITH 8, 20 AND 40 VALENCE ELECTRONS
Authors: Kumar Vijay
Published: November 2004

From studies on some clusters of metals and semiconductors, there appear some similarities in the structure of clusters with a given number of atoms and having the number of valence electrons corresponding to a shell closing, Here we present results of the atomic and electronic structure of a few other clusters with 20 and 40 valence electrons, namely Sb 4, Sn 5 and Sb 8 using the density functional molecular dynamics method. We suggest that the similarities in the structure and deviation from them may help to understand bonding characteristics in clusters and its evolution to bulk behaviour. Our results on Sb 8 cluster are preliminary but indicate that above room temperature its structure is two weakly interacting tetrahedra which is in general agreement with the observation of predominently antimony tetramers at T>300 K.
MEDIA EFFECTS ON THE OPTICAL ABSORPTION SPECTRA OF SILVER CLUSTERS EMBEDDED IN RARE GAS MATRICES
Authors: Fedrigo S. , Harbich W. , Buttet J.
Published: November 2004

The optical absorption of small mass selected Agn -clusters (n=7, 11, 15, 21) embedded in solid Ar, Kr and Xe has been measured. The absorption spectra show 1 to 3 major peaks between 3 and 4.5 eV, depending on the cluster size. Changing the matrix gas Ar→Kr→Xe induces a redshift which is comparable for all sizes studied and does not affect the main structure of the absorption spectra. We propose a scheme to estimate the gas phase value of the absorption energies which is in fair agreement with an estimation obtained by a simple model based on a Drude metal.
ELECTRON MICROSCOPY STUDY OF GRAPHITIC PARTICLES PRODUCED IN ARC-DISCHARGE EXPERIMENTS
Authors: Ugarte Daniel
Published: November 2004

We present a high resolution transmission electron microscopy investigation of carbon soot deposited on the surface of contact between carbon electrodes; the high spatial resolution of this technique being an especially powerful tool to directly visualize the atomic structures of small particles. We find a wide variety of shapes and structures, among which, most strikingly, concentric-shelled particles and coaxial graphene tubes. These tubes may present lengths longer than one micron, and diameters as small as one nanometer. Strong electron bombardment of the soot generates, as a final result, concentric-shelled, graphitic particles, with a remarkable spherical shape.
NEUTRON SCATTERING STUDIES OF FULLERENES
Authors: PRASSIDES KOSMAS
Published: November 2004

At low temperature, crystalline C 60 adopts a simple cubic structure whose stability is driven by optimisation of the intermolecular electrostatic interactions. Above 85 K, molecular motion is no longer frozen and the molecules shuffle between nearly-degenerate orientations, differing in energy by 11.4(3) meV. At 260 K, a first-order phase transition leads to a face-centred cubic structure, characterised by rapid isotropic molecular reorientational motion. In C 70, orientational ordering occurs near 270 K. The phonon spectra of C 60, superconducting K 3 C 60 and saturation-doped Rb 6 C 60 measured by inelastic neutron scattering in the energy range 0–200meV reveal substantial broadening in the superconducting fulleride of five-fold degenerate H g intramolecular modes both in the low-energy radial and the high-energy tangential part of the spectrum. This confirms the predictions of models based on intramolecular phonon-mediated pairing. The electron-phonon coupling strength is distributed over a wide range of energies (33–195 meV) as a result of the finite curvature of the fullerene spherical cage. No evidence is found for any significant electron-librational coupling.
THE PHONON FREQUENCY CHANGES IN FULLERENES WITH DOPING
Authors: Kusmartsev F.V.
Published: November 2004

We show that in fullerenes the phonon frequency of some vibrations depends upon the electron filling factor. The effect is related to the existence of orbital currents (orbital moments) which induce a frequency change of the vibration mode.
SCANNING TUNNELING MICROSCOPY USING IONIC CONDUCTION FOR IMAGING NON-CONDUCTIVE SPECIMENS
Authors: SHAO ZHIFENG , GAO CHAO , YUAN JIAN-YANG
Published: November 2004

It is shown that, theoretically, ionic conduction may be used in scanning tunneling microscopy to image surface topologies of partially hydrated specimens which are not electron conductors. The required experimental conditions are discussed, and the achievable resolution is shown to be in the order of nanometers.
TWO-STEP IONIZATION PROCESS OF THE DX CENTERS IN AlGaAs AND GaSb: EVIDENCE FOR A NEGATIVE-U CHARACTER OF THE DEFECT
Authors: DOBACZEWSKI L. , KACZOR P.
Published: November 2004

For the negative-U (two-electron) model of DX centers in III-V semiconductors the carrier exchange between the DX states and the conduction band must occur via an intermediate, thermodynamically unstable, one-electron D0 state (D−⇆ D0+e−⇆ D++2e−). In this review the experimental evidence for the existence of such an intermediate state is presented for the case of the DX(Te) centres in Al x Ga 1−x As and DX(S) in GaSb . The intermediate state of the process is strongly coupled to the lattice in the same ways as the ground state.
ON THE MATSUBARA-TOYOZAWA FORMALISM TO TREAT IMPURITY BANDS IN δ-DOPED QUANTUM WELLS
Authors: DA CUNHA LIMA I.C. , DA SILVA A. FERREIRA
Published: November 2004

We obtain the density of the ground and excited states for electrons bound to shallow donors in a δ-dopping of a quantum well. We use the Matsubara-Toyozawa technique to treat disorder. The impurity bands are calculated for a concentration of 9.4×109 cm −2. We show that for this concentration of interest the excited bands do not overlap the ground state.
ROOM TEMPERATURE TUNNELING CHARACTERISTICS OF ULTRA-SMALL NORMAL JUNCTIONS
Authors: REEVE M.D. , SYMKO O.G. , LI R.
Published: November 2004

Tunneling studies between a Scanning Tunneling Microscope (STM)-controlled fine NbN tip and a NbN thin film show single electron tunneling characteristics at room temperature. The I-V curves display the Coulomb blockade and the Coulomb staircase caused by single electron charging of a series combination of two tunnel junctions. These room temperature observations indicate that it may be possible to operate single-electron-based devices in non-cryogenic regimes.
PENETRATION DEPTH AND COHERENCE LENGTH IN SUPERCONDUCTING FULLERENE Rb3C60
Authors: POLITIS C. , SOKOLOV A.I. , BUNTAR V.
Published: November 2004

The penetration depth λ and the coherence length ξ in Rb 3 C 60 fullerene are determined by means of magnetic measurements in fields up to 50 kOe. For the Ginzburg-Landau coherence length the estimate ξ GL (0)=23 Å is obtained, while the magnitude of λ GL (0) extracted from the high-field data turns out to lie between 1200 and 1400 Å, with the upper value being more likely. Non-superconducting diamagnetic susceptibility is also measured and found to be equal to −(0.60±0.02)×10−5 which is an order of magnitude higher than that of undoped fullerene.
TWO-DIMENSIONAL BEHAVIOUR OF LAYERED HIGH-Tc SUPERCONDUCTORS
Authors: ARTEMENKO S. N. , LATYSHEV Yu. I.
Published: November 2004

High-T c superconductors (HTSs) have a layered structure, which strongly affects their physics. Bulk crystals exhibit the two-dimensional (2D) behaviour typical for superconducting films of atomic thickness. Fluctuation contribution to conductivity above mean-field critical temperature T c0 is characteristic to 2D superconductors. Finite resistivity in layered HTSs appears above Berezinskii-Kosterlitz-Thouless (BKT) transition T c , which is by several degrees smaller than T c0 . Below T c power-law I-V curves are observed. The transition and its main manifestations are described as a result of thermal creation of 2D-vortices with cores residing inside single superconducting layers. Magnetoresistive effects near the BKT transition are discussed briefly.
EXCITONIC MECHANISM FOR SUPERCONDUCTIVITY IN DOPED MOTT INSULATOR
Authors: CYROT MICHEL
Published: November 2004

We argue that when a Mott insulator is doped, it exists a range of concentration where two kinds of excitations coexist. Besides those of the usual Hartree-Fock metal, metallic excitons of very small energy persist. These excitons stems from the creation of an empty site surrounded by a virtual bound state in the band. Due to the strong interaction between electrons and metallic excitons, excitonic superconductivity is favoured.
TEMPERATURE DEPENDENCE OF Cu NUCLEAR RELAXATION RATES AND THE ANISOTROPY IN Y1Ba2Cu3O7 BELOW Tc: EVIDENCE FOR AN UNCONVENTIONAL PAIRING STATE
Authors: LU JIAN PING
Published: November 2004

The Cu nuclear relaxation rate W1 and their anisotropy ratio in the superconducting state are studied within a BCS pairing framework. Assuming that the strong scattering found in the normal state persists below T c , the temperature dependence of W1 for both s-wave and d-wave pairing are shown to agree with experiments. However only in the d-wave case is the anisotropy ratio W1a/W1c found to drop near T c and to increase at lower T, as observed in recent experiments. This provides strong evidence for the existence of the BCS coherence factors and an unconventional pairing state.
HUBBARD CHAIN EXTENDED TO INCORPORATE THE PEIERLS INSTABILITY
Authors: SCHAKEL ADRIAAN M. J.
Published: November 2004

The Hubbard chain is extended so as to incorporate the Peierls instability which is a fundamental property of one-dimensional metals. The resulting theory is analysed in the continuum. In the limit of low-energy and long-wavelength it is described by the O(3) nonlinear sigma model. It is argued that the theory has two phases. In one phase the excitation spectrum is gapless, while in the other phase it has a gap. This qualitative difference between the two states is shown to arise from the fact that in the massless phase the O(3) model acquires a topological term. Besides changing the spectrum of the theory, this term is shown to also change statistics.
AN OXYGEN CONTENT STUDY OF THE SmBa2Cu3O7−x SUPERCONDUCTOR
Authors: LOO B. H. , EMERSON M. T. , KATO T.
Published: November 2004

The Raman scattering and superconductivity characteristics of the SmBa 2 Cu 3 O 7−x samples with the (7 − x) values of 6.94, 6.83, 6.74, 6.57, and 6.37 are studied.
DIPOLAR FIELDS NEAR THE SURFACE FOR CRYSTALS WITH SIMPLE HEXAGONAL, HEXAGONAL CLOSE-PACKED AND DIAMOND STRUCTURE
Authors: DAS P. , KAR N.
Published: November 2004

The dipolar local field near the surface for simple hexagonal, hexagonal close-packed and diamond structure has been computed by considering a slab geometry. The technique of plane by plane summation for dipolar fields has been used and self-consistent field determined with large enough number of layers.
BIASED GaAs/AlGaAs HETEROJUNCTION AT LOW TEMPERATURE
Authors: FU Y. , CHEN Q. , WILLANDER M. , CHAO K. A.
Published: November 2004

Under various biased external conditions, we have investigated extensively the electronic energy sublevel structures in a common heterojunction cap/n+AlxGa1−xAs/spacer/GaAs-active-layer/buffer/substrate by a selfconsistent solution of the effective-mass Schrödinger equation and the Poisson equation. It is found that the depletion in the n+ Al x Ga 1−x As is incomplete if the doping concentration in this region is high, or the width of this region is wide, or the applied negative bias (cap electrically negative while substrate grounded) is not very large.
MICROWAVE ABSORPTION STUDIES ON HIGH-Tc SUPERCONDUCTORS AND RELATED MATERIALS X—ESR OF Gd IN Y-Ba-Cu-O BETWEEN ABOUT Tcand 600°C
Authors: SUGAWARA K. , TANAKA S.
Published: November 2004

Temperature dependence of ESR linewidth, ΔHPP, of Gd3+ in Y1−xGdxBa2Cu3Oy (x=0.2, 0.5 and 1) has been studied between about Tc (zero-resistance temperature) and about 600°C. For all the samples, ΔHPP progressively broadens as temperature approaches Tc from high temperature side, presumably due to inhomogeneous magnetic field distributions arising from superconductivity. On the contrary, ΔHpp is nearly linear in temperature between about 100 K and 600 K with temperature gradient, ∂(ΔHPP)/∂T~0.6 G/deg. The linear temperature dependence is assumed to be due to the Korringa relation. From the temperature gradient obtained above, JN(EF) was estimated as 0.0025, where J is the coupling coefficient between Gd spin S and conduction carrier’s spin S, and N(EF) is the density of states on the Fermi surface. In addition, by substituting an appropriate value for J, N(EF) was crudely estimated for the Y-Gd-Ba-Cu-O system.
THE GEOMETRIC PHASE IN NONLINEAR DISSIPATIVE SYSTEMS
Authors: NING C.Z. , HAKEN H.
Published: November 2004

We review the recent progress made in generalizing the concept of the geometric phase to nonlinear dissipative systems. We first illustrate the usual form of the parallel transport law with an elementary example of the parallel shift of a line on the complex plane. Important results about the non-adiabatical geometric (Aharonov and Anandan or AA) phase18 for the Schrödinger equations are reviewed in order to make a comparison with results for dissipative systems. Following the line of Ref. 21 we show that a geometric phase can be defined for dissipative systems with the cyclic attractors introduced in Ref. 21. Systems undergoing the Hopf bifurcation with a continuous symmetry are shown to possess such cyclic attractors. Examples from laser physics are discussed to exhibit the applicability of our formalism and the widespread existence of the geometric phase in dissipative systems defined in Ref. 21.
VOLTAGE-CURRENT CHARACTERISTICS AND MAGNETORESISTANCE OF BiPbSrCaCuO SILVER CLAMP THICK FILM
Authors: GUCHANG HAN , YUGUI WANG , HANMIN HAN , SHUNXI WANG
Published: November 2004

Bi(2223) silver clamp thick film with Jc=1.5×104A/cm2 at 77 K and 0 T was fabricated by a physical deposition method. Voltage-current characteristics and magnetoresistance were investigated in detail at low magnetic fields. It can be concluded that the transport Jc limitation of the present samples was still dominated by weak links although their connectivity has been greatly improved in comparison with bulk materials. The weak links may exert an effective pinning on flux lines. When the transport current exceeds the critical current of weak links their resistances change, just as does the flux flow resistance of traditional type-II superconductors. A history effect of the magnetoresistivity below a certain field (about 1.0 kG) was found at various constant measuring currents and can be ascribed to the Jc (H) characteristics and flux trapping both in the weak link network and the grains.
UNDERSCREENED KONDO NECKLACE
Authors: FAZEKAS P. , KEE HAE-YOUNG
Published: November 2004

It has been suggested recently by Gan, Coleman, and Andrei that studying the underscreened Kondo problem may help to understand the nature of magnetism in heavy fermion systems. Motivated by Doniach’s work on the S=1/2 Kondo necklace, we introduce the underscreened Kondo necklace models with S>1/2. The underscreened Kondo necklace is the simplest lattice model on which the competition between Kondo spin compensation, and magnetic ordering due to an RKKY-type interaction can be examined. We used the mean-field approximation to determine the phase diagram, and found that the low-temperature phase is always an x−y antiferromagnet. This contention is further supported by the derivation of the exact form of the effective Hamiltonian in the limit of very large Kondo coupling: it is found to be an antiferromagnetic x−y model for the residual S−1/2 spins. In general, the degree of moment compensation depends on both the Kondo coupling, and on S.
ALIGNMENT CHANGE BY MOISTURE ADSORPTION IN NEMATIC LIQUID CRYSTALS
Authors: BARBERO G. , KANIADAKIS G. , MIRALDI E. , RASTELLO M.L.
Published: November 2004

The abrupt change of the director orientation in nematic liquid crystals, for certain critical values of the cell thickness is described, and explained in terms of a change in surface polarization by moisture adsorption through the free external surface. The measured values of the director mean square angle with respect to the initial homeotropic direction are fitted by a stretched exponential function of the cell thickness with β=1/2. The behaviour of the three other parameters, i.e., the asymptotic deviation, the mean scaling length, and the critical thickness typical of a second order phase transition, is discussed as well.
TOPOLOGICAL AND SCALING PROPERTIES OF LINE DEFECTS IN Ni-Mo AMORPHOUS FILMS
Authors: SHANG C.H. , WANG Y.J. , LUO H.L. , LI H.D. , LIU B.X.
Published: November 2004

Odd loops of line defects were firstly found in the heavily irradiated amorphous films. A developed defect usually comprises two types of enclosed curves with different charges. Topologically, these defects are one-dimensional self-avoiding manifolds with variable connectivity. It is revealed that an attractive self-avoiding reaction and point-like defects dominate the evolution behavior of line defects. Scaling analyses show that both types of line defects are of statistical self-similarity with fractal dimensions between 1 and 2. Moreover, A self-consistent theory via self-avoiding tethered manifolds is proposed to account for the static and dynamic properties of the observed defects.
SURFACE SCATTERING EFFECT ON QUANTUM TRANSPORT IN THIN WIRES
Authors: QIU SHI-YUE
Published: November 2004

By following the theory of quantum transport and rough surface scattering developed by Tešanović et al., we present here a microscopic calculation of electronic conductivity in metallic thin wires. The rising of conductivity with the increase of the radius of a wire has a more complicated oscillatory structure than that found in thin films. The scattering on the rough surface in wires can lead both to the violation of Mattheissen's rule and to the localization of electronic states.
HELFRICH THEORY OF BIOMEMBRANES
Authors: XIE YU-ZHANG , OU-YANG ZHONG-CAN
Published: November 2004

In this paper we give a brief review on some of the recent results obtained from the curvature elasticity theory of biomembranes originally developed by Helfrich on fluid membranes and recently extended to tilted chiral lipid bilayers.
ELASTIC MODULI FOR THREE SUPERCONDUCTING PHASES OF Bi-Sr-Ca-Cu-O
Authors: DOMINEC J. , VAŠEK P. , SVOBODA P. , PLECHÁČEK V. , LAERMANS C.
Published: November 2004

We have measured the absolute values of longitudinal and transversal sound velocities in ceramic samples of Bi 2 Sr 2 Ca n-1 Cu n O 2n+4 (n=1, 2,3). We have compared various methods of calculation of "true" elastic moduli of matrix material. We used best of them to find the elastic moduli, sound velocities and Debye temperatures of the material. The calculated elastic moduli are low in a comparison with other oxide superconductors. The velocities and Debye temperatures increase with increasing n.
GROUND STATE INSTABILITY OF STRONGLY CORRELATED ELECTRONS
Authors: FERRAZ A. , OHMURA Y.
Published: November 2004

Summing up a special series of skeleton diagrams we show that in a strongly correlated electron fluid the proper irreducible electron-hole scattering kernel K is singular for sufficiently large Coulomb interactions. The instability of the electronic ground state is exhibited in the purely imaginary pole of K. This pole determines the decay rate of the unstable ground state and signals a phase transition of the whole electron system.
HALL EFFECT IN SUPERCONDUCTORS ABOVE Tc
Authors: ARONOV A. G. , RAPOROT A. B.
Published: November 2004

We consider the Aslamazov-Larkin term in the Hall conductivity near Tc, and find that the sign of this term is determined by ∂Tc/∂μ, where μ is Fermi level. We show that the AL term cannot explain the sign change of the Hall conductivity in high temperature superconductors. We also show that weak damping helicon waves exist in classical weak magnetic field due to the very strong increasing of AL term near Tc.
KINETICS OF SPINODAL DECOMPOSITION IN A CRITICAL POLYMER SOLUTION
Authors: KUBOTA K. , KUWAHARA N.
Published: November 2004

Spinodal decomposition in a critical mixture of polydimethylsiloxane and diethyl carbonate was investigated by a time-resolved light-scattering technique in the time region of the early to the intermediate stage of phase separation. The exponential growth of the scattered light intensity without changing the wave number of its peak was observed, in good agreement with the linearized theory of Cahn-Hillard. The quench depth dependences of the interdiffusion coefficient and of the wave number corresponding to the most dominant fluctuation show the three-dimensional Ising-model behavior indicating the validity of the symmetric law of critical-point universality.
DENSITY FUNCTIONAL THEORY AND THE CHERN-SIMONS FIELD APPROACH TO THE FRACTIONAL QUANTUM HALL EFFECT
Authors: DHARMA-WARDANA M. W. C.
Published: November 2004

In the effective field-theory of the fractional quantum Hall effect (FQHE), a purely formal Chern-Simons (CS) statistical gauge field is usually introduced and justified via the equivalence of the effective Lagrangian for the electromagnetic field. We identify this CS-field with a "physical field" arising from the exchange-correlation vector potential of current-density functional theory. The resulting Kohn–Sham picture of FQHE is compare with Laughlin's and Jain's theories.
CLUSTER ALGORITHM SPECIAL PURPOSE PROCESSOR
Authors: TALAPOV A. L. , SHCHUR L. N. , ANDREICHENKO V. B. , DOTSENKO VL. S.
Published: November 2004

We describe a Special Purpose Processor, realizing the Wolff algorithm in hardware, which is fast enough to study the critical behaviour of 2D Ising-like systems containing more than one million spins. The processor has been checked to produce correct results for a pure Ising model and for Ising model with random bonds. Its data also agree with the Nishimori exact results for spin glass. Only minor changes of the SPP design are necessary to increase the dimensionality and to take into account more complex systems such as Potts models.
IMPORTANCE-SAMPLING MONTE CARLO METHOD AND ENTROPY OF q-STATE POTTS MODEL
Authors: HUANG HSING-MEI
Published: November 2004

An importance-sampling Monte Carlo method is applied to the calculation of Γ(E), the number of states for a given energy E, and Γ(E, S), the number of states for given energy E and spin S, of antiferromagnetic two-dimensional q=2,3,4,5,6 Potts models. The entropy function is derived for various temperatures, and our results for the q=3 model show a continuous phase transition.
C60 UNDER PRESSURE
Authors: NÚÑEZ-REGUEIRO MANUEL
Published: November 2004

The high pressure experiments done on fullerenes are reviewed. C 60 has found to be stable up to about 20 GPa at room temperature and hydrostatic conditions. Application of stronger, or non-hydrostatic, pressures at room temperature can induce the formation of a partially sp3 bonded phase, that apparently conserves the fullerene cage. Extreme non-hydrostatic compressions above about 15 GPa can, though, break down the cage and produce amorphous or cubic diamond. Destruction of the cage at high temperatures has also been observed, but the resulting product is amorphous sp2 material. A preliminary pressure-temperature phase diagram for C 60 is proposed.
IMAGE ANALYSIS ON MASSIVELY PARALLEL COMPUTERS: AN ARCHITECTURAL POINT OF VIEW
Authors: MÉRIGOT A. , ZAVIDOVIQUE B.
Published: November 2004

Finding a parallel architecture adapted to a given class of algorithms is a central problem for architects. This paper presents a methodology to realize it, and provides an illustration using image analysis. First, we show a set of common basic operations that can be used to solve most image analysis problems. Then these movements are translated to fit some natural communications in a given architecture. The considered data movements (global operations on connected pixel sets) can express a large class of algorithms. Their implementation on exemplary massively parallel architectures (arrays, hypercubes, pyramids) is discussed.
HUMAN FACE RECOGNITION FROM A SINGLE FRONT VIEW
Authors: CHEN CHING-WEN , HUANG CHUNG-LIN
Published: November 2004

This paper presents a face recognition system which can identify the unknown identity effectively using the front-view facial features. In front-view facial feature extractions, we can capture the contours of eyes and mouth by the deformable template model because of their analytically describable shapes. However, the shapes of eyebrows, nostrils and face are difficult to model using a deformable template. We extract them by using the active contour model (snake). After the contours of all facial features have been captured, we calculate effective feature values from these extracted contours and construct databases for unknown identities classification. In the database generation phase, 12 models are photographed, and feature vectors are calculated for each portrait. In the identification phase if any one of these 12 persons has his picture taken again, the system can recognize his identity.
SEGMENTATION OF BILEVEL IMAGES USING MATHEMATICAL MORPHOLOGY
Authors: CHENG JIN-CHANG , DON HON-SON
Published: November 2004

This paper presents the results of a study on the use of morphological skeleton transformation to segment gray-scale images into bilevel images. When a bilevel image (such as printed texts and machine tools) is digitized, the result is a gray-scale image due to the point spread function of digitizer, non-uniform illumination and noise. Our method can recover the original bilevel image from the gray-scale image. The theoretical basis of the algorithm is the physical structure of the skeleton set. A connectivity property of the gray-scale skeleton transformation is used to separate and remove the background terrain. The object pixels can then be obtained by applying a global threshold. Experimental results are given.
BASIC PUZZLE GRAMMARS AND ISOSCELES RIGHT TRIANGLES
Authors: SUBRAMANIAN K. G. , SIROMONEY R. , DARE V. R. , SAOUDI A.
Published: November 2004

Two methods of generating isosceles right triangles by basic puzzle grammars are presented. The methods use two different sets of tiles to tile the triangular region. This is of interest in view of the fact that the set of isosceles right triangles is a nontrivial example of a two-dimensional language which cannot be generated by any regular array grammar.
ANALOG MOS VECTOR MULTIPLIERS FOR THE IMPLEMENTATION OF SYNAPSES IN ARTIFICIAL NEURAL NETWORKS
Authors: SALAM FATHI M.A. , CHOI MYUNG-RYUL
Published: November 2004

All-MOS analog vector-vector multipliers are described and designed for the implementation of the linear multiplication between analog signals and analog synaptic weights in artificial neural networks (ANNs). Employing these multipliers, large-scale artificial neural networks can be implemented using fewer MOS transistors than are required by implementations employing the so-called Gilbert multiplier.

PSPICE circuit simulations have been extensively executed in order to quantify the performance of these multipliers by measuring the following specifications: maximum percentage error, output offset, X or Y nonlinearity, X or Y feedthrough, small-signal bandwidth, and slew rate.

An 11-dimensional analog vector multiplier has been designed on a 40-pin MOSIS TINYCHIP with analog pads using the MAGIC VLSI tools and has been fabricated using 2 μm CMOS n-well process via MOSIS.
A CAD METHOD FOR THE DESIGN OF A DOUBLY-MATCHED BROADBAND NETWORK HAVING COMPLEX TRANSMISSION ZEROS
Authors: ZHU YI-SHENG , CHEN WAI-KAI
Published: November 2004

In this paper, it is shown that in the solution of the double matching problem given by Carlin and Yarman there does not exist a one-to-one correspondence between the output impedance Zq(s) and the transducer power gain function when the matching network contains the complex transmission zeros contributed by the common factors of the numerator and denominator of Zq(s). Also Youla’s conditions imposed on the chain parameters are extended and applied to the passive, lumped, lossless, and nonreciprocal two-port networks.

Based on the above discussion, a CAD method using the chain parameters is proposed to solve the double matching problem where the equalizer may have complex transmission zeros. The result permits us to design a general doubly-matched network, the amplitude and phase of which are both required to be matched. Finally, an example is given to describe the iterative approximation process and its computations.
FEASIBILITY PROOF FOR ARBITRARILY TIGHT PHASE EQUALIZATION
Authors: KUMMERT ANTON , FETTWEIS ALFRED
Published: November 2004

In this paper, the phase equalization problem for continuous-time us well as for discrete-time linear systems is considered from a theoretical point of view. The purpose is thus not to present an efficient algorithm for solving this problem in practice, but to offer a mathematical proof that an arbitrarily tight approximation of the linear phase behavior in any given finite frequency interval is always feasible. In a first step it is shown that the problem can be reduced to the equalization of the phase of a real first-order all-pass section. This simplified problem is investigated in Sec. 4.2 of the paper.