bluuebunny/crossref_metadata_2025 huggingface dataset:
TOROIDAL SOLITON SOLUTIONS IN O(3)N NONLINEAR SIGMA MODEL
Authors: WERESZCZYŃSKI A.
Published: October 2004

A set of N three-component unit scalar fields in (3+1) Minkowski spacetime is investigated. The highly nonlinear coupling between them is chosen to omit the scaling instabilities. The multi-soliton static configurations with arbitrary Hopf numbers are found. Moreover, the generalized version of the Vakulenko–Kapitansky inequality is obtained. The possibility of attractive as well as repulsive interaction between hopfions is shown. A noninteracting limit is also discussed.
PARTON SATURATION APPROACH IN HEAVY QUARK PRODUCTION AT HIGH ENERGIES
Authors: GONÇALVES V. P. , MACHADO M. V. T.
Published: October 2004

The high parton density regime of the quantum chromodynamics (QCD), where the physics of parton saturation is expected to be dominant, is briefly discussed. Some phenomenological aspects of saturation are described, mainly focusing on possible signatures of the nonlinear QCD dynamics in the heavy quark production in electron–proton/nucleus collisions. Implications of these effects in the heavy quark production in ultraperipheral heavy-ion collisions are also presented.
A REVIEW OF THE N-BOUND AND THE MAXIMAL MASS CONJECTURES USING NUT-CHARGED dS SPACE–TIMES
Authors: CLARKSON RICHARD , GHEZELBASH A. M. , MANN ROBERT B.
Published: October 2004

The proposed dS/CFT correspondence remains an intriguing paradigm in the context of string theory. Recently it has motivated two interesting conjectures: the entropic N-bound and the maximal mass conjecture. The former states that there is an upper bound to the entropy in asymptotically de Sitter space–times, given by the entropy of pure de Sitter space. The latter states that any asymptotically de Sitter space–time cannot have a mass larger than the pure de Sitter case without inducing a cosmological singularity.

Here we review the status of these conjectures and demonstrate their limitation. We first describe a generalization of gravitational thermodynamics to asymptotically de Sitter space–times, and show how to compute conserved quantities and gravitational entropy using this formalism. From this we proceed to a discussion of the N-bound and maximal mass conjectures. We then illustrate that these conjectures are not satisfied for certain asymptotically de Sitter space–times with NUT charge. We close with a presentation of explicit examples in various space–time dimensionalities.
END-TO-END DISTANCE DISTRIBUTION OF FORCE STRETCHED CHAINS RECONSTRUCTION BY MAXIMUM-ENTROPY METHOD
Authors: DAI LURU , LIU FEI , OU-YANG ZHONG-CAN
Published: October 2004

Using the maximum-entropy method, the end-to-end distance distribution of the force stretched chain is calculated from the moments of the distribution, which can be obtained from the extension-force curves recorded in single-molecule experiments. If one knows force expansion of the extension through the (n-1)th power of force, it is enough information to calculate the n moments of the distribution. The method is examined with force stretched chain models, Gaussian chain and excluded-volume chain on two-dimension lattice. The method reconstructs all distributions precisely. The method also is applied to force stretched complex chain molecules: the hairpin and secondary structure conformations. We find that the distributions of homogeneous chains of two conformations are very different: there are two independent peaks in hairpin distribution; while only one peak is observed in the distribution of secondary structure conformations. Our discussion also shows that the end-to-end distance distribution may discover more critical physical information than the simpler extension-force curves can give.
DIVERSITY AND ADAPTATION IN LARGE POPULATION GAMES
Authors: WONG K. Y. MICHAEL , LIM S. W. , LUO PEIXUN
Published: October 2004

We consider a version of large population games whose players compete for resources using strategies with adaptable preferences. The system efficiency is measured by the variance of the decisions. In the regime where the system can be plagued by the maladaptive behavior of the players, we find that diversity among the players improves the system efficiency, though it slows the convergence to the steady state. Diversity causes a mild spread of resources at the transient state, but reduces the uneven distribution of resources in the steady state.
DISORDER DRIVEN MELTING OF MOVING VORTEX MATTER IN LAYERED SUPERCONDUCTORS
Authors: NIE QING-MIAO , LUO MENG-BO , CHEN QING-HU , HU XIAO
Published: October 2004

The current-driven three-dimensional frustrated anisotropic XY model with strong disorder is simulated to model the moving vortex matter in layered superconductors. The equilibrium disordered state can be driven to a moving Bragg glass (BrG) by applying an external current. As the pinning strength increases, the moving BrG can melt into a moving smectic via a first-order phase transition.
NON-EQUILIBRIUM STATISTICAL DISTRIBUTION, PROJECT GREEN FUNCTIONS AND STABILIZING QUANTUM COMPUTING FOR OPEN SYSTEM
Authors: BI QIAO , YAO XIAOJING , GU BIN , RUDA H. E.
Published: October 2004

Using the kinetic equation of subdynamics and the suitable time ordering rule we present a type of irreversible Liouville equation and nonlinear Liouville equation for open quantum systems. We also found a spectral relation for obtaining the non-equilibrium statistical distribution based on the boundary conditions which consistent with H theorem. Furthermore, a formalism of non-equilibrium project Green functions is given, and a non-perturbative method to solve the irreversible Liouville equation is studied. Finally, we give a model of spin-based quantum computing to show that the decoherence free states can be constructed using the non-perturbative approach.
THE FINITE-SIZE EFFECT ON THE ENTANGLEMENT OF THE QUANTUM ISING CHAIN
Authors: ZHANG LIFA , TONG PEIQING
Published: October 2004

By using the concurrence, the entanglement of a quantum Ising chain is studied numerically. It is found that there is a gap in the concurrence of the nearest-neighbor spins at the quantum phase transition point for the chain with even spins. The gap disappears as the number of the spins goes to infinite. Except for the critical point, the derivatives of the concurrence display the similar scaling behavior as that of the odd-spin chain.
THE MONTE–CARLO SIMULATION OF THE PERMEABILITY OF K ION CHANNELS
Authors: AN HAI-LONG , ZHAN YONG , LIU JIN-WEI , ZHANG SU-HUA , ZHAO TONG-JUN
Published: October 2004

In this paper, by introducing the collision model of the K ion channel, the maximum value of ions inward the channel per second, the average velocity of ions in the channels and the average time of every ion passing through the channel are obtained. Moreover they are reconciled with the experimental data. Base on the experimental data, the empiristic potential function is deduced. With the Monte–Carlo simulation, the curve of average velocity versus time and average displacement versus time are calculated by resolving the over-damping Langevin equation with Gaussian-white noise. They are according with the experimental dada well.
A SELF-ADAPTIVE MODEL OF ACTOR-COLLABORATION NETWORK
Authors: JIANG YUMEI , XU TIAN , HE DA-REN
Published: October 2004

We suggest a self-adaptive model for a description of actor-collaboration. Suppose that the numbers of actors and directors increase as time progresses (with different velocity). Each of the people is randomly given a style coefficient and a famousness coefficient, which vary on time according to his achievements in every year. A director can conduct more films and an actor can be invited to perform in more films in condition they have a higher famousness coefficient. Our numerical simulation results show that the actor-collaboration network described by this model is both small-world network and scaling-free network. All the important statistical parameters obtained by the simulation are in a good agreement with the statistical results. We also suggest a new parameter, which is addressed as "degree of connexity". Its distribution shows a new power law.
PERIODICITY OF CHAOTIC TRAJECTORIES IN REALIZATIONS OF FINITE COMPUTER PRECISIONS AND ITS IMPLICATION IN CHAOS COMMUNICATIONS
Authors: WANG SHIHONG , LIU WEIRONG , LU HUAPING , KUANG JINYU , HU GANG
Published: October 2004

Fundamental problems of periodicity and transient process to periodicity of chaotic trajectories in computer realization with finite computation precision is investigated by taking single and coupled Logistic maps as examples. Empirical power law relations of the period and transient iterations with the computation precisions and the sizes of coupled systems are obtained. For each computation we always find, by randomly choosing initial conditions, a single dominant periodic trajectory which is realized with major portion of probability. These understandings are useful for possible applications of chaos, e.g., chaotic cryptography in secure communication.
COMPLICATED ELECTRICAL ACTIVITIES IN CARDIAC TISSUE
Authors: SHIAU YUO-HSIEN , HSUEH MING-PIN , HSEU SHU-SHYA , YIEN HUEY-WEN
Published: October 2004

It has become widely accepted that ventricular fibrillation, the most dangerous cardiac arrhythmias, is a major cause of death in the industrialized world. Alternans and conduction block have recently been related to the progression from ventricular tachycardia to ventricular fibrillation. From the point of view in cellular electrophysiology, ventricular tachycardia is the formation of reentrant wave in cardiac tissue. And ventricular fibrillation arises from subsequent breakdown of reentrant wave into multiple drifting and meandering spiral waves. In this paper, we numerically study pulse and vortex dynamics in cardiac tissue. Our numerical results include 1:1 normal sinus rhythm, 2:1 conduction block, complete conduction block, spiral wave, and spiral breakup. All of our numerical findings can be corresponding to clinical measurements in electrocardiogram. Various electrical activities in cardiac tissue will be discussed in detail in the present manuscript.
A DISCRETE SIMULATION OF TUMOR GROWTH CONCERNING NUTRIENT INFLUENCE
Authors: SUN L. , CHANG Y. F. , CAI X.
Published: October 2004

We develop a 2-D discrete model to simulate malignant cells growing in healthy tissues using a thermodynamic method on the basis of Potts model. After introducing a malignant seed in a healthy tissue, we use a set of adjustment factors, including the interaction between cells and nutrient, to simulate the growth of malignant cells under different environments. This allows us to investigate the effects of environment on malignant cell growth and the formation of cancer.
NONLINEAR DYNAMICS OF FLOW-REACTION COUPLING IN POROUS MEDIA AND APPLICATION TO IN SITU LEACHING URANIUM MINING
Authors: TAN KAI-XUAN , WANG QING-LIANG , LIU ZE-HUA , HU E-MING
Published: October 2004

When a reactive fluid flows through a porous rock it can dissolve some minerals and increase the porosity and permeability. The positive feedback between fluid flow and mineral dissolution can lead to the complexity of the propagation of dissolution front and the formation of finger flow-focusing reaction area. As an example for in situ leaching Uranium mining, the simulation results indicate that the propagation of dissolution front is complex such as finger and more complicated reaction front morphologies. The nonlinearity of flow-reaction coupling and instability of dissolution front morphologies can lead to unleaching area and affect the rate of recovery of mineral resource.
EXPERIMENTAL STUDY OF ENERGY ABSORPTION PROPERTIES OF GRANULAR MATERIALS UNDER LOW FREQUENCY VIBRATIONS
Authors: HU MAO-BIN , KONG XIANG-ZHAO , WU QING-SONG , ZHU ZHEN-GANG
Published: October 2004

The low frequency vibration energy absorption properties of granular materials have been investigated on an Invert Torsion Pendulum (ITP). The energy absorption rate of granular material changes nonlinearly with amplitude under low frequency vibration. The frequency of ITP system increases a little with granular materials in the holding cup. The vibration frequency of ITP system does not change with time.
VIBRATIONAL STUDIES AND RESONANT INTERACTION BETWEEN LOCALIZED AND EXTENDED MODES IN Si:O UNDER PRESSURE
Authors: HSU L. , McCLUSKEY M. D.
Published: October 2004

The relaxation mechanisms of local vibrational modes in solids are of central importance in understanding how such modes decay into phonons, the diffusion of impurities, and the loss of hydrogen passivation in technologically important materials. Interstitial oxygen in silicon is a model system for studying the relaxation of local vibrational modes into extended vibrational modes by measuring the interactions between the two. We have used hydrostatic pressure to bring the antisymmetric stretch mode of Si :18 O i into resonance with the second harmonic of the 18 O i resonant mode and observed an anticrossing between the two vibrational modes near pressures of 4 GPa. A theoretical model of this interaction produced excellent agreement with the experimentally observed frequencies and linewidths.
URBAN TRANSIT SYSTEM AS A SCALE-FREE NETWORK
Authors: WU JIANJUN , GAO ZIYOU , SUN HUIJUN , HUANG HAIJUN
Published: October 2004

Many systems can be represented by networks as a set of nodes joined together by links indicating interaction. Recently studies have suggested that a lot of real networks are scale-free, such as the WWW, social networks, etc. In this paper, discoveries of scale-free characteristics are reported on the network constructed from the real urban transit system data in Beijing. It is shown that the connectivity distribution of the transit network decays as a power-law, and the exponent λ is about equal to 2.24 from the simulation graph. Based on the scale-free network topology structure of the transit network, if only transit "hub nodes" are controlled well, the transit network can resist random failures (such as traffic congestion, traffic accidents, etc.) successfully.
ENTANGLEMENT IN THE XY HEISENBERG MODEL
Authors: TIAN XIN , LIN JIA-TIH , LIU LIANG , REN DE-LONG
Published: October 2004

We investigate the thermal entanglement of two-qubit anisotropic Heisenberg XY model in the presence of an external nonuniform magnetic field B along the z-axis. Concurrence, the measure of entanglement is calculated and its property is studied in different cases. Two best models, Ising model under a uniform magnetic and isotropic model in a nonuniform magnetic field, are discovered. In the two models, the critical temperature Tc (above which there is no entanglement) can be enhanced and its concurrence is maximal.
OBSERVATION OF PERIODIC, QUASIPERIODIC AND CHAOTIC LOCALIZED EXCITATIONS IN NONLINEAR DIATOMIC MACRO-LATTICE
Authors: LOU SON-YUE , YU JUN , LIN JI , HUANG GUOXIANG , ZHANG JIA-KUNG
Published: October 2004

In one-dimensional damped and parametrically excited diatomic macro-lattice, some kinds of recurrences for localized envelope excitations are observed. When drive frequency is 3.40 Hz and drive amplitude lies between 0.43 mm (the lower cutoff value) and 0.52 mm, the acoustic lower cutoff soliton mode is quite stable. As the drive amplitude increases to 0.52 mm ~ 0.55 mm under the same drive frequency, the amplitude of the soliton changes periodically and/or quasiperiodically. For larger drive amplitude Ac (0.55 mm < Ac < 0.76 mm ), the recurrence of the soliton amplitude becomes chaotic. Finally if the drive amplitude exceeds the upper cutoff value, ~0.76 mm, the localized structure is totally destroyed.
PHASE DIAGRAM OF THE GAUGE INVARIANT TWO SPECIES ISING MODEL
Authors: GONNELLA GIUSEPPE , STRAMAGLIA SEBASTIANO
Published: October 2004

We study the phase diagram of a Z(2) Higgs-gauge model with two species of Ising matter in D=2 and D=3. Differently from the case with only one Ising species, this model exhibits a transition also at zero gauge coupling. Loop expansions and mappings on the 8-vertex and the Ashkin–Teller models are used to study the nature of the transitions in the extreme regions of the phase diagram. Relevant differences with respect to the case of one species of Ising spins are found.
CALCULATION OF DISCRETE-SPECTRUM CONTRIBUTIONS TO RELATIVISTIC LAMB-SHIFT OF THE 1S HYDROGENIC STATE
Authors: SEKE J.
Published: October 2004

By using a general formula for exact relativistic transition matrix elements, derived in our previous paper, unrenormalized (finite) and renormalized level-shift contributions to the Lamb-shift of the 1s state, stemming from individual discrete states as well as from the whole discrete spectrum, are calculated.
LINEAR MAGNETORESISTANCE CAUSED BY THE INTERFERENCE OF OPEN ORBITS
Authors: PARK MI-AE , KIM YONG-JIHN
Published: October 2004

We find that the interference of two open orbits modeled by two noncollinear cylindrical Fermi surfaces leads to a linear magnetoresistance. The interference occurs only when the magnetic field is slightly tilted from the perpendicular to the plane defined by the cylinders’ axes. There exist experimental data which reveal a linear magnetoresistance. Some may possibly be explained by the interference effect.
ALTERNATIVE MICROSCOPIC APPROACH TO THE PHOTOABSORPTION OF SMALL CLUSTERS
Authors: GRABOWSKI S. , GARCIA M.E. , BENNEMANN K.H.
Published: October 2004

A Wannier-type electronic theory to calculate self-consistently the photoabsorption spectra of small clusters is presented. This approach, that applies to systems with mainly localized electrons, permits a detailed analysis of the dependence of the absorption cross-section on atomic structure and cluster size. In addition the approach also allows a transparent identification of the optical excitations contributing to the different absorption peaks. By applying this theory to neutral and ionized mercury clusters one finds that both exciton- and plasmon-like excitations are present in the absorption spectra. Furthermore the dependence of the optical response on short- and long-range Coulomb interactions, on structural changes of the system and on the specific bonding character of the cluster is studied. It is demonstrated that the broadening of the collective excitations in small clusters with localized electrons depends sensitively on the atomic structure, in particular at the surface. The limitations of this theory and its extension to systems having also delocalized electrons, like noble- and transition-metal clusters are discussed.
MEASUREMENTS OF ELECTROMAGNETIC SHIELDING EFFECT USING HTSC MATERIALS
Authors: VIDYALAL V. , RAJASREE K. , VALLABHAN C.P.G.
Published: October 2004

A simple experimental set-up is described to measure the electromagnetic shielding property of high Tc superconducting samples. Measurements were performed using HTSC materials in the form of laser ablated thin films, powders and sintered pellets. Samples used were Gd-123 in pure and doped form as well as a few Bi-based superconducting ceramics. For comparison, similar measurements were carried out on metals like aluminium, copper and μ metal. Very effective shielding was observed for HTSC materials compared to the conventional materials mentioned above. However it also depended on the sample types and poor shielding was observed for powdered HTSC material in comparison to thin films prepared by laser ablation.
ON THREE INTEGRALS ARISING IN THE THEORY OF ANISOTROPIC CRITICALITY
Authors: MILLEV YONKO T.
Published: October 2004

Three integrals encountered in earlier studies of anisotropic criticality (anisotropic dispersion laws characterised by the coupling constant f) are solved in terms of elementary functions. The nature of the singularity for the case f→1 which corresponds to an effectively reduced dimensionality has been revealed. Double power-series representations for the integrals are also found and some mathematical implications and by-products are discussed. The advance relates to a prospective full-scope analysis of dipolar criticality.
CRITICAL BEHAVIOR OF A TWO COMPONENT COMPLEX FIELD MODEL AND SYMMETRY OF ITS RENORMALIZATION GROUP STRUCTURE
Authors: BLAGOEVA E.J.
Published: October 2004

The critical behavior of a two-component (n/2=2) complex field model applied to heavy-fermion and high-Tc superconductors is studied by the renormalization group in d=4−∊. Fixed points with new scaling properties are discovered and their critical exponents are presented beyond the two-loop order. A generalization for n/2 >2 carried out.
OPTICAL ABSORPTION IN THE SOLITON MODEL FOR POLYACETYLENE
Authors: MICHIELSEN KRISTEL , RAEDT HANS DE
Published: October 2004

A quantum molecular dynamics technique is used to compute the optical absorption at room-temperature for the soliton model for trans-polyacetylene in the semiclassical limit. Our simulation data for the optical absorption for dopant concentrations below 6% are in good agreement with experiment.
FEW-ANYON SPECTRA IN A HARMONIC OSCILLATOR POTENTIAL
Authors: GHOSH RANJAN KUMAR , RAO SUMATHI
Published: October 2004

We study the problem of four and five anyons in a harmonic oscillator potential and make some exact statements regarding its energy spectra. We show that the spectra exhibit some mirror symmetric (reflection symmetric about the semionic statistics point θ=π/2) features analogous to the mirror symmetry in the two and three anyon spectra.
PARTICLE TRAPPING BY OSCILLATING FIELDS: CONNECTING SQUEEZING WITH COOLING
Authors: BASEIA B. , VYAS REETA , BAGNATO V.S.
Published: October 2004

The first observation of the squeezing effect outside the optical domain was reported very recently for trapped atoms [D. M. Meekhof et al., Phys. Rev. Lett.76, 1796 (1996)]. Pursuing this line and a sequel of previous works of ours we employ a model by Glauber and a method of invariants by Lewis and Riesenfeld to establish a connection between the squeezing and the cooling effects in the system. From this connection the occurrence of squeezing could be detected through the measurement of the dispersion in the variable [Formula: see text] and of the temperature.
ON THE GENERATION OF INTERMEDIATE NUMBER SQUEEZED STATE OF THE QUANTIZED RADIATION FIELD
Authors: BASEIA B. , DE LIMA A.F. , BAGNATO V.S.
Published: October 2004

Recently, a new state of the quantized radiation field — the intermediate number squeezed state (INSS) — has been introduced in the literature: it interpolates between the number state |n> and the squeezed state |z, α>=Ŝ(z)|α>, and exhibits interesting nonclassical properties as antibunching, sub-Poissonian statistics and squeezing. Here we introduce a slight modification in the previous definition allowing us a proposal to generate the INSS. Nonclassical properties using a new set of parameters are also studied.
LONG-RANGE ORDER FOR THE 3-STATE SQUARE LATTICE POTTS MODEL WITH ANTIFERROMAGNETIC “THE MOVE OF THE KNIGHT” INTERACTIONS
Authors: BAKAEV A.V. , KABANOVICH V.I.
Published: October 2004

The 3-state square lattice Potts model with interactions of spins belonging to the different sublattices, the nearest-neighbor (NN) interaction and “the move of the knight” (MK) antiferromagnetic interactions which also couples spins on the sublattice A to spins on B, is studied by Monte Carlo simulations. It is shown that the MK-interactions stabilizes the BSS phase in two dimensions, preserving macroscopic degeneracy of the ground state. In a range of competing ferromagnetic (NN) interactions “stripes” or “double-stripes” phases are found.
STUDIES OF SURFACE-INDUCED LAYER-BY-LAYER TWO-STAGE PHASE TRANSFORMATIONS
Authors: JIN A.J. , HUANG C.C. , CHOU C.F. , CHAO C.Y. , HO J.T.
Published: October 2004

Utilizing our high-resolution ac calorimeter, optical reflectivity, and electron diffraction, we have found a few very interesting phenomena associated with the free-standing films of the N-(4-n-butyloxybenzylidene)-4-n-octylaniline (4O.8) compound. Upon cooling from the smectic-A phase, the outer surface layers display a distinct hexatic-B order and subsequently transforms into crystal-B phase through a two-stage transformation. Each stage is found to be first order. The film exhibits a layer-by-layer ordering transitions developed from the film/vapor interface inwardly.
CRITICAL REGION AT THE NEMATIC-ISOTROPIC PHASE TRANSITION
Authors: MUKHERJEE PRABIR K.
Published: October 2004

The phase transition from isotropic liquid to nematic liquid crystal is a weak first order one. The present paper investigate the possibility of the critical region near the isolated critical point at the first order nematic-isotropic phase transition line.
AHARONOV-CASHER EFFECT WITHOUT LINE CHARGE
Authors: LEE TAEYEON
Published: October 2004

It is shown that the case considered by Casella, which has no path-enclosed charge and was claimed to have different topology from the original Aharonov-Casher case of line charge, is actually equivalent to the Aharonov-Casher case.
PHYSICAL PROPERTIES OF WATER WITH IE STRUCTURES
Authors: LO SHUI-YIN , LO ANGELO , CHONG LI WEN , TIANZHANG LIN , HUA LI HUI , GENG XU
Published: October 2004

Various physical properties of water with I E structures are measured. Compared with oridinary water, there is an approximate 20% decrease in dielectric constant for I E water at MHz as an increase of emf generated by I E water between two identical stainless steel electrodes, and an increase in resistivity to AC current. Fluorescence at 298 nm peak is seen in I E water but not in ordinary water. From the thermal variation of UV absorption spectrum, one can estimate the amount of I E structure to be up to 3%. The elevation of boiling point due to I E structure can then be used to calculate the molecular weight of I E structure to be the same as water molecule.
NEW METHOD FOR TREATING RELAXATION PROCESSES: DAMPED HARMONIC OSCILLATOR AND THE JAYNES-CUMMINGS MODEL WITH CAVITY LOSSES
Authors: SEKE J.
Published: October 2004

In the present paper a new technique for treating relaxation processes, based on the author’s self-consistent projection-operator method, is developed. This new technique, which yields (instead of a master equation for a reduced density operator) equations of motion for probability amplitudes for a reduced set of states of the total system, opens a new way for treating relaxation processes. The applicability of the new method is demonstrated in the case of a damped harmonic oscillator and in that of the Jaynes-Cummings model with cavity losses.
WIGNER OPERATOR AND SQUEEZING FOR ROTATED QUADRATURE PHASES
Authors: FAN HONG-YI , XIAO MIN
Published: October 2004

We introduce the Wigner operator [Formula: see text] for the rotated quadrature phases and use the technique of integration within an ordered product of operators to derive its explicitly simpler form. Based on this, the mutual relations between [Formula: see text] and the corresponding marginal probability distribution operator can be easily revealed. The Wigner function theory is thus be recasted into a more elegant and concise formalism. The squeezing in rotated quadrature phase is discussed with the same method.
DEFORMABLE SUPERCONDUCTORS: A RENORMALIZATION GROUP APPROACH
Authors: BUSIELLO G.
Published: October 2004

Deformable superconductors, i.e., superconductors with structural instabilities are considered as a model for high T c , superconductors. A generalized Ginzburg-Landau theory is studied by renormalization group theory. The fixed points and their stability properties are discussed using the ∊ analysis.
STUDY OF LASER ABLATION IN LIQUIDS USING PULSED PHOTOACOUSTIC TECHNIQUE
Authors: HARILAL S.S. , ISSAC RIJU C. , BINDHU C.V. , NAMPOORI V.P.N. , VALLABHAN C.P.G.
Published: October 2004

Laser ablation processes in liquid benzene, toluene and carbon disulphide have been investigated by pulsed photoacoustic technique using 532 nm radiation from a frequency doubled Q-switched Nd:YAG laser. The nature of variation of photoacoustic signal amplitude with laser energy clearly indicates that different phenomena are involved in the generation of photoacoustic effect and these are discussed in detail. Our results suggest multiphoton induced photofragmentation as the most plausible interaction process occurring during laser ablation in these liquids.
MEAN FIELD RENORMALIZATION GROUP FOR ISING MODELS WITH S≥1
Authors: LARA D. PEÑA , PLASCAK J.A.
Published: October 2004

The mean field renormalization group is extended in order to study spin-S Ising models (S≥1) by introducing additional parameters in the Hamiltonians of the clusters, in the same spirit as the mean field approach. These new parameters are then consistently obtained according to finite size scaling ideas and quite good results are obtained, even for the smallest choice of the clusters. Moreover, the mean value of the square of the spin along the second-order transition line can also be obtained from the present formalism.
THE NORMAL STATE RESISTIVITY OF A SUPERCONDUCTING FILM IN AN EXTERNAL STATIC ELECTRIC FIELD IN YBa2Cu3O7−x
Authors: LINGAM LYDIA S. , SHRIVASTAVA KESHAV N.
Published: October 2004

We propose two mechanisms for the variation of resistance of a film as a function of applied electric field. The resistivity calculated for the field-driven movement of the mobile charge carriers in the normal state of a superconductor in the static approximation varies as the square root of the electric field, ρ∝E1/2 only as long as the dielectric constant is independent of the field. We also predict that the resistivity of a system with conduction electrons localized along a 1-dimensional chain varies as the square root of the applied electric field. We have found that for the electric field larger than about half of the break down field, E >E BD /2, the measured resistivity varies as the square root of the electric field, ρ∝E1/2. Thus both of the theoretical approximations are in agreement with the experimental measurements of the normal state resistivity of YBa 2 Cu 3 O 7−x.
THE PHONON MECHANISM OF THE COLD FUSION
Authors: LIU FU-SUI
Published: October 2004

This paper shows that the longitudinal acoustic phonon can induce a time-dependent hopping rate of deuteron in PdD, and leads to the cold fusion.
HALF-OPERATORISATION OF A FUNCTION AND PHYSICAL APPLICATIONS
Authors: PARK S.U. , BATCHELOR M.T. , OH I.K.
Published: October 2004

We define an half-operatorisation of a function by using its Fourier series such that the Fourier series basis changes into exponential phase operators with the Fourier coefficients remaining intact. We define and discuss the half-operator version of various Fourier Series properties. One application is the master field describing the large N limits of matrix models. We also define an half-operatorisation using gauge equivalent exponential phase operators which have a shifted vacuum.
ANOMALOUS HALL EFFECT IN WEAK PINNING HIGH-Tc SUPERCONDUCTORS
Authors: ZHU B.Y.
Published: October 2004

Taking into account both pinning and thermal fluctuation and employing the single flux flow model of Wang, Dong, and Ting (WDT), we have performed numerical study to investigate the flux motion in the weak pinning environment in the mixed-state of high-Tc superconductors. We find that there exist two kinds of weak pinning regime, one possesses low pinning concentration but strong individual pinning potentials, the other consists of high pinning concentration but weak individual pinning potentials for the double sign reversal of Hall resistivity ρxy. Moreover, our simulation and analysis suggest that the weak collective pinning effect may not be a good reason for the abnormal Hall effect. These results are well consistent with recent measurement of Bi2Sr2CaCu2O8 (BSCCO), Tl2Ba2CaCu2O8 (TBCCO) and HgBa2CaCu2O6 (HBCCO) and collective pinning theories for Hall effect.
FERROMAGNETISM IN THE HUBBARD MODEL WITH AN INFINITE-RANGE HOPPING
Authors: PIERI PIERBIAGIO
Published: October 2004

We prove, as recently conjectured, that the ground state of the Hubbard Hamiltonian with an infinite-range hopping, when the number of electrons Ne=N+1 (N being the number of sites), is ferromagnetic fully polarized. This turns out to be a simple consequence of a general theorem proven by Mielke on flat-band ferromagnetism.
INFLUENCE OF THE COUNTER-ROTATING TERMS ON THE RABI OSCILLATIONS IN THE POLYATOMIC JAYNES-CUMMINGS MODEL WITH CAVITY LOSSES FOR INITIAL FOCK-STATE FIELDS
Authors: SEKE J.
Published: October 2004

The significance of the counter-rotating terms in the polyatomic Jaynes-Cummings model with cavity losses is demonstrated. Numerical results for the time evolution of the atomic population inversion and dipole moment for an initial Fock-state field with different photon numbers are presented for various cavity dampings. The appearance of new steady states for the population inversion and the mean-photon number under the influence of the counter-rotating terms is pointed out. Namely, as is shown, the presence of “virtual photons”, produced by the counter-rotating terms, leads to these effects.
STRUCTURAL, ELECTRICAL AND MAGNETIC PROPERTIES OF HIGH-TcYBa1.5Ca0.5Cu3O6+δ SUPERCONDUCTOR
Authors: POP I. , HOMORODEAN L. , BURDA I. , ANDRECUT M.
Published: October 2004

A high-Tc YBa 1.5 Ca 0.5 Cu 3 O 6+δ superconductor was synthesized, with the critical temperature Tc=84.9 K. The crystalline structure is orthorhombic with the lattice parameters a=3.8665 Å, b=3.9217 Å and c=11.7652 Å, characteristic for the 123 superconductors. The diamagnetic transition in the temperature dependence of the magnetic susceptibility strongly depends on the recycling of the samples and the onset of superconductibility is depressed by the magnetic field intensity.
ASYMMETRIC CELLS AND ROTATING RINGS IN CELLULAR FLAMES
Authors: GUNARATNE GEMUNU H. , EL-HAMDI MOHAMED , GORMAN MICHAEL , ROBBINS KAY A.
Published: October 2004

Theoretical analysis and experimental results are presented to demonstrate the universal characteristics of parity-breaking bifurcations for pattern-forming systems in a circular domain. Ordered patterns of concentric rings of cells which form in a premixed flame on a circular burner at low pressure are used to demonstrate these ideas. Cells belonging to stationary rings are symmetric, while those of rotating rings are not. The important characteristics of the experimental results are reproduced in a theoretical model which can be numerically integrated in polar coordinates. Normal form equations for the Fourier–Bessel coefficients of this model lead to parity breaking.
STUDY ON THE SUPERCONDUCTIVITY IN Y1−xPrxBa2Cu3−yLiyO7−δ
Authors: SONG HONGQING , CAO GUANGHAN , XU ZHU’AN , ZHANG QIRUI
Published: October 2004

Polycrystalline samples of Y 1−x Pr x Ba 2 Cu 3−y Li y O 7−δ (y=0, 0.05) have been prepared and characterized by X-ray powder diffraction and temperature dependence of resistivity. The T c of Y 1−x Pr x Ba 2 Cu 2.95 Li 0.05 O 7−δ decreases monotonically with increasing Pr content, but the normalized T c (T c /T c ( max )) of Y 1−x Pr x Ba 2 Cu 2.95 Li 0.05 O 7−δ is higher than that of Y 1−x Pr x Ba 2 Cu 3 O 7−δ for a fixed Pr content. This result indicates that the effect of T c suppression by Pr doping becomes weaker in the Li-doped system. Considering the Li substitution effect on the structural details, we argue that the Pr–O covalent bonding effect is responsible for the superconductivity suppression.
MINISUPERSPACE MODEL FOR REVISED CANONICAL QUANTUM GRAVITY
Authors: MONTANI GIOVANNI
Published: October 2004

We present a reformulation of the canonical quantization of gravity, as referred to the minisuperspace; the new approach is based on fixing a Gaussian (or synchronous) reference frame and then quantizing the system via the reconstruction of a suitable constraint; then the quantum dynamics is re-stated in a generic coordinates system and it becomes dependent on the lapse function.

The analysis follows a parallelism with the case of the non-relativistic particle and leads to the minisuperspace implementation of the so-called kinematical action as proposed in Ref. 1 (here almost coinciding also with the approach presented in Ref. 2).

The new constraint leads to a Schrödinger equation for the system, i.e. to non-vanishing eigenvalues for the super-Hamiltonian operator; the physical interpretation of this feature relies on the appearance of a "dust fluid" (non-positive definite) energy density, i.e. a kind of "materialization" of the reference frame.

As an example of minisuperspace model, we consider a Bianchi type IX Universe, for which some dynamical implications of the revised canonical quantum gravity are discussed. We also show how, on the classical limit, the presence of the dust fluid can have relevant cosmological issues.

Finally we upgrade our analysis by its extension to the generic cosmological solution, which is performed in the so-called long-wavelength approximation. In fact, near the Big-Bang, we can neglect the spatial gradients of the dynamical variables and proceed to implement, in each space point, the same minisuperspace paradigm valid for the Bianchi IX model.
DOTTED AND UNDOTTED ALGEBRAIC SPINOR FIELDS IN GENERAL RELATIVITY
Authors: CAPELAS DE OLIVEIRA E. , RODRIGUES W. A.
Published: October 2004

We investigate using Clifford algebra methods the theory of algebraic dotted and undotted spinor fields over a Lorentzian spacetime and their realizations as matrix spinor fields, which are the usual dotted and undotted two component spinor fields. We found that some ad hoc rules postulated for the covariant derivatives of Pauli sigma matrices and also for the Dirac gamma matrices in General Relativity cover important physical meaning, which is not apparent in the usual matrix presentation of the theory of two components dotted and undotted spinor fields. We discuss also some issues related to the previous one and which appear in a proposed "unified" theory of gravitation and electromagnetism which use two components dotted and undotted spinor fields and also paravector fields, which are particular sections of the even subundle of the Clifford bundle of spacetime.
ISOVECTOR COLLECTIVE RESPONSE FUNCTION OF NUCLEAR MATTER AT FINITE TEMPERATURE
Authors: BOZKURT KUTSAL
Published: October 2004

We study isovector collective excitations in nuclear matter by employing the linearized Landau–Vlasov equation with and without a non-Markovian binary collision term at finite temperature. We calculate the giant dipole resonance (GDR) strength function for finite nuclei using the Steinwedel–Jensen model and also by Thomas–Fermi approximation, and we compare them for 120 Sn and 208 Pb with experimental results.
CHANNELING OF POSITRONS THROUGH PERIODICALLY BENT CRYSTALS: ON THE FEASIBILITY OF CRYSTALLINE UNDULATOR AND GAMMA-LASER
Authors: KOROL A. V. , SOLOV'YOV A. V. , GREINER W.
Published: October 2004

The electromagnetic radiation generated by ultra-relativistic positrons channeling in a crystalline undulator is discussed. The crystalline undulator is a crystal whose planes are bent periodically with the amplitude much larger than the interplanar spacing. Various conditions and criteria to be fulfilled for the crystalline undulator operation are established. Different methods of crystal bending are described. We present the results of numeric calculations of spectral distributions of the spontaneous radiation emitted in the crystalline undulator and discuss the possibility to create the stimulated emission in such a system in analogy with the free electron laser. A careful literature survey covering the formulation of all essential ideas in this field is given. Our investigation shows that the proposed mechanism provides an efficient source for high energy photons, which is worth studying experimentally.
THE USE OF COLOR IN THE SCIENTIFIC VISUALIZATION OF ACOUSTICAL PHENOMENA
Authors: SPARROW VICTOR W. , ROCHAT JUDITH L. , BARD BENJAMIN A.
Published: October 2004

Color is commonly used in representing scientific data, especially as color output devices have become widely available. The misuse of color can lead to confusing or even misleading representations of data. The purpose of this paper is to provide a review of guidelines for using color effectively, specifically aimed at the computational acoustics community. The question of whether or not to use color at all is initially raised, and gray-scale is suggested for appropriate cases. Human color deficiencies in technical audiences are then described, and the consequential choices of equally-accessible color schemes are discussed. The topics of human color perception models, hypsometric tints, contoured plots, and histogram equalization are introduced. Color palettes specifically suited for acoustical phenomena, such as linear and dB magnitudes, scales for positive and negative data, circular palettes for phase, and methods for illustrating different classes of phenomena (e.g., wave types) on a single plot, are discussed in detail. Color examples and Mathematica code are provided, and final recommendations are made for choosing effective color schemes.
TOWARDS A HIGHLY ACCURATE IMPLEMENTATION OF THE KIRCHHOFF APPROACH FOR COMPUTATIONAL AEROACOUSTICS
Authors: MEADOWS KRISTINE R. , ATKINS H.L.
Published: October 2004

This paper describes the development of high-order Kirchhoff algorithms and confirms that high-order accuracy can be achieved with the Kirchhoff approach when high-order integration and interpolation are properly implemented. This paper also establishes guidelines for enhancing accuracy of a given order property when the Kirchhoff formula is applied to results obtained from a computational fluid dynamics (CFD) solution. Accuracy is shown to increase when the Kirchhoff surface size is minimized. Reduction of the Kirchhoff surface size also enhances efficiency of the calculation because the size of the relatively expensive CFD computation is reduced. The accuracy of the Kirchhoff approach is also enhanced by increasing the density of information along the Kirchhoff surface. This increase in information is necessary because evaluation of the Kirchhoff integrand at the retarded time demands higher spatial resolution than the integration of the time-dependent nonlinear equations of the CFD calculation. A procedure has been developed that addresses the Kirchhoff resolution requirements without sacrificing efficiency. The error reduction realized with this procedure matches that realized with CFD mesh refinement, with almost no increase in cost.
3-D PROPAGATION ISSUES AND MODELS
Authors: TOLSTOY A.
Published: October 2004

Why do we care about 3-D propagation models? This paper will review the importance and development of presently available 3-D propagation models along with their capabilities and limitations. We will also see some computational predictions illustrating dramatic 3-D effects in shallow water situations.
PERFECTLY MATCHED LAYERS FOR ELASTODYNAMICS: A NEW ABSORBING BOUNDARY CONDITION
Authors: CHEW W.C. , LIU Q.H.
Published: October 2004

The use of perfectly matched layers (PML) has recently been introduced by Berenger as a material absorbing boundary condition (ABC) for electromagnetic waves. In this paper, we will first prove that a fictitious elastodynamic material half-space exists that will absorb an incident wave for all angles and all frequencies. Moreover, the wave is attenuative in the second half-space. As a consequence, layers of such material could be designed at the edge of a computer simulation region to absorb outgoing waves. Since this is a material ABC, only one set of computer codes is needed to simulate an open region. Hence, it is easy to parallelize such codes on multiprocessor computers. For instance, it is easy to program massively parallel computers on the SIMD (single instruction multiple data) mode for such codes. We will show two- and three-dimensional computer simulations of the PML for the linearized equations of elastodynamics. Comparison with Liao’s ABC will be given.
NON-PARABOLIC MARCHING ALGORITHM FOR SOUND FIELD CALCULATION IN THE OCEAN WAVEGUIDE
Authors: VORONOVICH A.
Published: October 2004

An algorithm is presented for calculating sound field in the inhomogeneous ocean waveguide. It does not involve parabolic approximation and can be considered as principally exact (at least for 2D inhomogeneities of the sound speed field). On the other hand, it is “marching” and can be easily implemented as a computer code (note, that marching in this case proceeds in “backward” direction, i.e. towards the source). Those features of the code are similar to couple mode algorithm (COUPLE) developed originally by R. Evans. The principal difference is that suggested code does not assume piecewise constant approximation of the waveguide properties with respect to horizontal coordinates. As a result, the horizontal steps of marching can be increased significantly. The estimate of the efficiency of the approach as compared to stepwise couple modes method is given. The results of the code testing with the help of benchmark problem as well as calculation of sound propagation through a strong inhomogeneity formed by the sub-arctic front are presented.

The present version of the code can be used to calculate entries of scattering matrix (S-matrix) for the ocean waveguide as well as travel times of different modes (derivatives of phases of corresponding entries with respect to frequency). A priori restrictions on S-matrix (reciprocity and energy conservation) are also given, and some objective quantitative criterion of the accuracy of the numerical algorithms formulated in terms of S-matrix is suggested.
INDUCTION AND FUSION OF FUZZY PROTOTYPES
Authors: RODRÍGUEZ INÉS GONZÁLEZ , LAWRY JONATHAN , BALDWIN JIM F.
Published: October 2004

In the sequel, we shall be concerned with the automated induction of prototypes to represent a database in a way that combines transparency and accuracy. More precisely, our aim is to automatically summarize the information from a set of data using prototypes and simultaneously decide on the number of prototypes needed to the represent the data adequately. We propose to use fuzzy prototypes, which correspond to groupings of similar objects represented by tuples of fuzzy sets over attribute universes. In the case of numerical attributes, the universes will be discretized using linguistic variables and the attribute values will be described by fuzzy sets on words. To learn the prototypes, we shall present an algorithm inspired by hierarchical clustering techniques, which makes use of new measures of prototype similarity and of prototype addition. Also, a pruning algorithm will be incorporated which uses a new heuristic measure of prototype quality to fuse overly specific prototypes. The potential of the resulting method will be illustrated by its application to a number of classification problems and comparing its performance with that of previous approaches in the literature.
THE QUEST FOR RINGS ON BIPOLAR SCALES
Authors: GRABISCH MICHEL , DE BAETS BERNARD , FODOR JÁNOS
Published: October 2004

We consider the interval ]-1, 1[ and intend to endow it with an algebraic structure like a ring. The motivation lies in decision making, where scales that are symmetric w.r.t. 0 are needed in order to represent a kind of symmetry in the behaviour of the decision maker. A former proposal due to Grabisch was based on maximum and minimum. In this paper, we propose to build our structure on t-conorms and t-norms, and we relate this construction to uninorms. We show that the only way to build a group is to use strict t-norms, and that there is no way to build a ring. Lastly, we show that the main result of this paper is connected to the theory of ordered Abelian groups.