bluuebunny/crossref_metadata_2025 huggingface dataset:
ON THE BEHAVIOR AT INFINITY OF THE FUNDAMENTAL SOLUTION OF TIME DEPENDENT SCHRÖDINGER EQUATION
Authors: YAJIMA KENJI
Published: July 2002

We show that the asymptotic behavior at infinity of the fundamental solution of the initial value problem for the free Schrödinger equation or of the harmonic oscillator at non-resonant time is stable under subquadratic perturbations. We also show that the same is true for the phase and the amplitude of the Fourier integral operator representing the propagator.
INFINITE DIMENSIONAL ALGEBRAS AND 2+1 DIMENSIONAL FIELD THEORY: YET ANOTHER VIEW OF gl(∞) SOME NEW ALGEBRAS
Authors: HOPPE JENS
Published: July 2002

Over the past years, associative algebras have come to play a major role in several areas of theoretical physics. Firstly, it has been realized that Yang Baxter algebras [1] constitute the relevant structure underlying 1+1 dimensional integrable models; in addition, their relation to braid groups, the theory of knots and links, and the exchange algebras of 1+1 dimensional conformal field theories [2] has been quite well understood by now. Secondly, deformations of Poisson structures that appeared in 2+1 dimensional field theories as infinite dimensional symmetry algebras possess underlying associative structures, which have also been studied in some detail (concerning higher spin theories see, e.g., [3, 4] and references therein, concerning the enveloping algebra of sl(2, C) see, e.g., [5], concerning deformations of diff AT2 — the Lie algebra of infinitesimal area preserving diffeomorphisms of the Torus — see [6, 7, 8, 9]). Ideas on how both investigations could eventually converge (i.e., a relation between 2+1 and 1+1 dimensions) have, e.g., been expressed in [10].

As indicated by the two subtitles there will be two parts to my paper: the first one presents a view on something I met long ago [11], and recently got interested in again [5, 7, 9, 12], while the second part introduces some algebraic structures that seem to be interesting, and possibly new.
REMARKS ON DECAY OF CORRELATIONS AND WITTEN LAPLACIANS II — ANALYSIS OF THE DEPENDENCE ON THE INTERACTION
Authors: HELFFER BERNARD
Published: July 2002

This is the continuation of previous notes on the subject referred as [10] and devoted to the analysis of Laplace integrals attached to the measure exp -Φ(X)dX for suitable families of phase Φ appearing naturally in the context of statistical mechanics. The main application treated in [10] was a semi-classical one (Φ=Ψ/h and h→0), and the assumptions on the phase were related to weak non-convexity. We analyze here in the same spirit the case when the coefficient of the interaction [Formula: see text] possibly is large and give rather explicit lower bounds for the lowest eigenvalue of the Witten Laplacian on 1-forms. We also analyze the case small [Formula: see text] by discussing first an unpublished proof of [2] and then an alternative approach based on the analysis of a family of 1-dimensional Witten Laplacians. We also compare our results to those by Sokal's approach. In the last paper of this series [11], we shall analyze, in a less explicit way, but in a more general context, applications to the logarithmic Sobolev inequality.
IRREDUCIBLE UNITARY REPRESENTATIONS OF SUp,q I: THE DISCRETE SERIES
Authors: WILSON RAJ , TANNER ELIZABETH
Published: July 2002

A class of irreducible unitary representations in the discrete series of SUp,q is explicitly determined in a space of holomorphic functions of three complex matrices. The discrete series, which is the set of all square integrable representations, corresponds to a compact subgroup of SUp,q. The relevant algebraic properties of the group SUp,q are discussed in detail. For a degenerate irreducible unitary representation an explicit construction of the infinitesimal generators of the Lie algebra [Formula: see text] in terms of differential operators is given.
SCALING PROPERTIES OF DECONSTRUCTION INTERFACES IN DISORDERED MEDIA
Authors: SANCHEZ JUAN R.
Published: July 2002

The scaling properties of interfaces generated by a disaggregation model in 1+1 dimensions are studied by numerical simulations. The model presented here for the disaggregation process takes into account the possibility of having quenched disorder in the bulk under deconstruction. The disorder can be considered to model several types of irregularities appearing in real materials (dislocations, impurities). The presence of irregularities makes the intensity of the attack to be not uniform. In order to include this effect, the computational bulk is considered to be composed by two types of particles: those particles which can be easily detached and other particles that are not sensible to the etching attack. As the detachment of particles proceeds in time, the dynamical properties of the rough interface are studied. The resulting one-dimensional surface show self-affine properties and the values of the scaling exponents are reported when the interface is still moving near the depinning transition. According to the scaling exponents presented here, the model must be considered to belong to a new universality class.
PERCOLATION THRESHOLDS, CRITICAL EXPONENTS, AND SCALING FUNCTIONS ON SPHERICAL RANDOM LATTICES AND THEIR DUALS
Authors: HUANG MING-CHANG , HSU HSIAO-PING
Published: July 2002

Bond-percolation processes are studied for random lattices on the surface of a sphere, and for their duals. The estimated threshold is 0.3326 ± 0.0005 for spherical random lattices and 0.6680 ± 0.0005 for the duals of spherical random lattices, and the exact threshold is conjectured as 1/3 for two-dimensional random lattices and 2/3 for their duals. A suitably defined spanning probability at the threshold, Ep(pc), for both spherical random lattices and their duals is 0.980±0.005, which may be universal for a 2-d lattice with this spanning definition. The shift-to-width ratio of the distribution function of the threshold concentration and the universal values of the critical value of the effective coordination number can be extended from regular lattices to spherical random lattices and their duals. The results of critical exponents are consistent with the assertion from the universality hypothesis. Finite-size scaling is also examined.
Hypothalamic Effects of Millimeter Wave Irradiation Depend on Location of Exposed Acupuncture Zones in Unanesthetized Rabbits
Authors: Vorobyov Vasily V. , Khramov Robert N.
Published: July 2002

On nine unanesthetized male rabbits, the frequency spectra of hypothalamic electrogram (EEG) were studied during low intensity (10 mW/cm2) millimeter wave (55–75 GHz) exposure to various acupuncture points (zone): auricular, cranial and corporal. The chances of occurrence of significant (p < 0.05) changes in the EEG spectra during irradiation versus. sham experiments were equal to 31, 21 and 5%, respectively. Exposure to auricular zone reduced the EEG power in narrow bands with central frequencies of 5.3, 15.9 Hz and increased ones of 2.6, 3.2, 6.9, 7.9, 11.5 and 25.6 Hz. The main effect of exposure to cranial zone was similar — changes at 15.9 and 25.6 Hz only. The data obtained demonstrate that the responsiveness of the central nervous system to low intensity millimeter wave radiation may depend on the location of the exposed acupuncture zone.
QUASIPARTICLE MODEL OF THE QUARK/GLUON PLASMA IN A STRONG MAGNETIC FIELD
Authors: GIBILISCO MARINA
Published: July 2002

In this paper, I study the effect of a strong magnetic field on the quark/gluon plasma, whose properties are investigated by using a quasiparticle model with effective thermal masses for both the quarks and the gluons. This analysis is performed looking at the perspectives opened by the study of the interior of neutron stars, where large magnetic fields, as high as 1018 G, might exist; the high densities present in their core might also favor the matter deconfinement. I show that the presence of a large magnetic field has an important influence on the equation of state of the deconfined plasma; the astrophysical relevance of this effect is also discussed, together with the present possibilities to detect a quark matter star.
REPARAMETRIZATION-INVARIANT PATH INTEGRAL IN GR AND "BIG BANG" OF QUANTUM UNIVERSE
Authors: PAWLOWSKI M. , PERVUSHIN V. N.
Published: July 2002

The reparametrization-invariant generating functional for the unitary and causal perturbation theory in general relativity in a finite space–time is obtained. The region of validity of the Faddeev–Popov–DeWitt functional is studied. It is shown that the invariant content of general relativity as a constrained system can be covered by two "equivalent" unconstrained systems: the "dynamic" (with "dynamic" evolution parameter as the metric scale factor) and "geometric" (given by the Levi–Civita type canonical transformation to the action-angle variables where the energy constraint converts into a new momentum).

"Big Bang," the Hubble evolution, and creation of matter fields by the "geometric" vacuum are described by the inverted Levi–Civita transformation of the geomeric system into the dynamic one. The particular case of the Levi–Civita transformations are the Bogoliubov ones of the particle variables (diagonalizing the dynamic Hamiltonian) to the quasiparticles (diagonalizing the equations of motion). The choice of initial conditions for the "Big Bang" in the form of the Bogoliubov (squeezed) vacuum reproduces all stages of the evolution of the Friedmann–Robertson–Walker universe in their conformal (Hoyle–Narlikar) versions.
EXACT RENORMALIZATION GROUP EQUATIONS AND THE FIELD THEORETICAL APPROACH TO CRITICAL PHENOMENA
Authors: BAGNULS C. , BERVILLIER C.
Published: July 2002

After a brief presentation of the exact renormalization group equation, we illustrate how the field theoretical (perturbative) approach to critical phenomena takes place in the more general Wilson (nonperturbative) approach. Notions such as the continuum limit and the renormalizability and the pressure of singularities in the perturbative series are discussed.
ABSENCE OF NONLOCAL COUNTERTERMS IN THE GAUGE BOSON PROPAGATOR IN AXIAL-TYPE GAUGES
Authors: JOGLEKAR SATISH D. , MISRA A.
Published: July 2002

We study the two-point function for the gauge boson in the axial-type gauges. We use the exact treatment of the axial gauges recently proposed that is intrinsically compatible with the Lorentz-type gauges in the path-integral formulation and has been arrived at from this connection and which is a "one-vector" treatment. We find that in this treatment, we can evaluate the two-point functions without imposing any additional interpretation on the axial gauge 1/(η·q)qtype poles. The calculations are as easy as the other treatments based on other known prescriptions. Unlike the "uniform-prescription"/LM prescription, we note, here, the absence of any nonlocal divergences in the two-point proper vertex. We correlate our calculation with that for the Cauchy Principal Value prescription and find from this comparison that the two-point proper vertex differs from the CPV calculation only by finite terms. For simplicity of treatment, the divergences have been calculated here with η2> 0 and these have a smooth light cone limit.
LARGE SCALE PATHOLOGY AND GRAVITOMAGNETIC RESONANCES IN STATIC VII0 × VIII SPACE–TIMES WITH MIXED MATTER SOURCES
Authors: DARIESCU CIPRIAN , DARIESCU MARINA-AURA
Published: July 2002

The aim of the present paper is to analyze some globally pathologic properties in worlds described by a class of static planary symmetric exact solutions with g44 = - cosh 2(αz), pointing out some unusual (pathological) features such as cosmic-time traps, non-spacelike imprisonments of test particle trajectories and structures very much like the ones of a BTZ black hole. Finally, we deal with the exactly solvable analytical behavior of the magnetostatic fields, stressing the significant difference from the Minkowskian case, namely a nonsingular, almost total, confinement of the field in a finite spacelike region, which we termed as a gravitomagnetic resonance, entirely due to the large scale pathology of such a Universe.
THE NONCOMMUTATIVE SUPERSYMMETRIC NONLINEAR SIGMA MODEL
Authors: GIROTTI H. O. , GOMES M. , RIVELLES V. O. , DA SILVA A. J.
Published: July 2002

We show that the noncommutativity of space–time destroys the renormalizability of the 1/N expansion of the O(N) Gross–Neveu model. A similar statement holds for the noncommutative nonlinear sigma model. However, we show that, up to the subleading order in 1/N expansion, the noncommutative supersymmetric O(N) nonlinear sigma model becomes renormalizable in D=3. We also show that dynamical mass generation is restored and there is no catastrophic UV/IR mixing. Unlike the commutative case, we find that the Lagrange multiplier fields, which enforce the supersymmetric constraints, are also renormalized. For D=2 the divergence of the four-point function of the basic scalar field, which in D=3 is absent, cannot be eliminated by means of a counterterm having the structure of a Moyal product.
FERMION STATES ON THE SPHERE S2
Authors: ABRIKOSOV A. A.
Published: July 2002

We solve for the spectrum and eigenfunctions of Dirac operator on the sphere. The igenvalues are nonzero whole numbers. The eigenfunctions are two-component spinors which may be classified by representations of the SU(2) group with half-integer angular momenta. They are special linear combinations of conventional spherical spinors.
TOWARDS NONPERATURBATIVE RENORMALIZABILITY OF QUANTUM EINSTEIN GRAVITY
Authors: LAUSCHER O. , REUTER M.
Published: July 2002

We summarize recent evidence supporting the conjecture that four-dimensional Quantum Einstein Gravity (QEG) is nonperturbatively renormalizable along the lines of Weinberg's asymptotic safety scenario. This would mean that QEG is mathematically consistent and predictive even at arbitrarily small length scales below the Planck length. For a truncated version of the exact flow equation of the effective average action we establish the existence of a non-Gaussian renormalization group fixed point which is suitable for the construction of a nonperturbative infinite cutoff-limit. The cosmological implications of this fixed point are discussed, and it is argued that QEG might solve the horizon and flatness problem of standard cosmology without an inflationary period.
COLD TRAPPED ATOMS: A MESOSCOPIC SYSTEM
Authors: HUANG KERSON
Published: July 2002

The Bose–Einstein condensates recently created in trapped atomic gases are mesocopic systems, in two senses: (a) Their size fall between macroscopic and microscopic systems; (b) They have a quantum phase that can be manipulated in experiments. We review the theoretical and experimental facts about trapped atomic gases, and give examples that emphasize their mesocopic characters. One is the dynamics of collapse of a condensate with attractive interactions. The other is the creation of a one-dimensional kink soliton that can be used as a mode-locked atom laser.
STUDYING THE CONTACT POINT AND INTERFACE MOVING IN A SINUSOIDAL TUBE WITH LATTICE BOLTZMANN METHOD
Authors: FANG HAI-PING , FAN LE-WEN , WANG ZUO-WEI , LIN ZHI-FANG , QIAN YUE-HONG
Published: July 2002

The multicomponent nonideal gas lattice Boltzmann model by Shan and Chen (S-C) is used to study the immiscible displacement in a sinusoidal tube. The movement of interface and the contact point (contact line in three-dimension) is studied. Due to the roughness of the boundary, the contact point shows "stick-slip" mechanics. The "stick-slip" effect decreases as the speed of the interface increases. For fluids that are non-wetting, the interface is almost perpendicular to the boundaries at most time, although its shapes at different position of the tube are rather different. When the tube becomes narrow, the interface turns a complex curves rather than remains simple menisci. The velocity is found to vary considerably between the neighbor nodes close to the contact point, consistent with the experimental observation that the velocity is multi-values on the contact line. Finally, the effect of three boundary conditions is discussed. The average speed is found different for different boundary conditions. The simple bounce-back rule makes the contact point move fastest. Both the simple bounce-back and the no-slip bounce-back rules are more sensitive to the roughness of the boundary in comparison with the half-way bounce-back rule. The simulation results suggest that the S-C model may be a promising tool in simulating the displacement behaviour of two immiscible fluids in complex geometry.
THE MBX CHALLENGE COMPETITION: A NEUTRON MATTER MODEL
Authors: BAKER GEORGE A.
Published: July 2002

In this paper I report my solution to MBX Challenge Competition. Namely, the Bertsch, nonparametric model of neutron matter is analyzed and strong indications are found that, in the infinite system limit, the ground state is a Fermi liquid with an effective mass.
MAGNETIC AND ELECTRIC BEHAVIOUR OF SOME LEAD-BORATE GLASSES WITH MANGANESE IONS
Authors: ARDELEAN I. , SIMON V. , IONCU V. , FILIP S. , FLORA M.
Published: July 2002

Magnetic susceptibility and electric resistivity measurements have been performed on x MnO ·(100-x)[2 B 2 O 3· PbO ] glasses with 030 mol% the manganese ions experience negative magnetic superexchange interactions. From Curie constant values we have established that in these glasses both Mn 2+ and Mn 3+ ions are present, which explains their magnetic and electric behaviour. The conductivity increases while the conductivity activation energy decreases with the MnO content. In order to analyse the conductivity data, we have considered in all glasses a polaronic model for conduction.
IN SITU CHARACTERISATION OF CALCITE GROWTH AND INHIBITION USING ATOMIC FORCE MICROSCOPY
Authors: REYHANI MANIJEH M. , OLIVEIRA ALLAN , PARKINSON GORDON M. , JONES FRANCA , ROHL ANDREW L. , OGDEN MARK I.
Published: July 2002

Real time in situ monitoring of calcite growth and inhibition on the cleavage plane [Formula: see text] is investigated using atomic force microscopy (AFM). Calcite growth and inhibition were studied using a Molecular Imaging microscope in contact mode, equipped with an in situ fluid cell. As has been reported previously, it is observed that calcite growth from aqueous solution is by motion of mono-molecular steps, and dissolution by a combination of step motion and etch pit expansion. The measured step heights were between 2.7 to 3 Å. Our aim is to study the effects of a range of phosphonate-based crystal growth inhibitors of related structure, in order to provide insight into the mechanism of inhibition as a function of the additive structure. Results of this study demonstrate the effect of inhibitors on the growth steps and terraces on the [Formula: see text] surface of calcite in real time. The organic additives bind to the crystal surface, with selective binding to the step edges particularly evident in some cases. In other cases, it appears that the additive acts by binding to the terraces on the crystal surface, resulting in inhibition by coating the surface. Efforts to correlate the observations made by atomic force microscopy with bulk crystallization experiments have been made.
SCATTERING PHASE SHIFTS IN QUASI-ONE-DIMENSION
Authors: SINGHA DEO P. , BANDOPADHYAY SWARNALI , DAS SOURIN
Published: July 2002

Scattering of an electron in quasi-one-dimensional quantum wires have many unusual features, not found in one, two or three-dimensions. In this work we analyze the scattering phase shifts due to an impurity in a multi-channel quantum wire with special emphasis on negative slopes in the scattering phase shift versus incident energy curves and the Wigner delay time. Although at first sight, the large number of scattering matrix elements show phase shifts of different character and nature, it is possible to see some pattern and understand these features. The behavior of scattering phase shifts in one-dimension can be seen as a special case of these features observed in quasi-one-dimensions. The negative slopes can occur at any arbitrary energy and Friedel sum rule is completely violated in quasi-one-dimension at any arbitrary energy and any arbitrary regime. This is in contrast to one, two or three dimensions where such negative slopes and violation of Friedel sum rule happen only at low energy where the incident electron feels the potential very strongly (i.e. there is a very well defined regime, the WKB regime, where FSR works very well). There are some novel behavior of scattering phase shifts at the critical energies where S-matrix changes dimension.
STUDY OF LOCAL STRUCTURE IN UNDER-DOPED La2-xSrxCuO4-y BY POLARIZED EXAFS
Authors: GARG K. B. , SANCHEZ C. , GARCIA J. , BLASCO J. , SINGHAL R. K. , DALELA S. , SAINI N. L.
Published: July 2002

Temperature dependence of local structure of the CuO 2 plane has been studied by in plane polarized (E//ab) Cu K-edge extended X-ray absorption fine structure (EXAFS) experiments on an under-doped single crystal of superconducting La1.87Sr0.13CuO 4-y system with T c =32  K . The temperature dependence of the Debye–Waller factors for the Cu-O and Cu-La/Sr pairs are determined. We find that the motion of Cu and O atoms in the Cu-O bond is partially correlated at higher temperatures, going over to an uncorrelated motion at lower temperatures. The results are discussed in terms of the local lattice instabilities and stripes as reported in other systems.
RELATION BETWEEN SPIN AND PSEUDOSPIN IN STRONGLY CORRELATED ELECTRONIC SYSTEMS
Authors: SUSHKOV O. P.
Published: July 2002

Dyson equation which relates the single hole Green's functions for a given pseudospin and given spin is derived for t-J model. This equation is applied to explain the experimental spectra for angle resolved photoemission in insulating Copper Oxide.
LOCAL MODES AROUND THE FERROMAGNETIC IMPURITIES IN THE TWO-DIMENSIONAL HEISENBERG ANTIFERROMAGNETS
Authors: SONG YUN
Published: July 2002

The behaviors of the spin-wave excitations around the ferromagnetic impurities in the two-dimensional spin-1/2 Heisenberg antiferromagnets are investigated for the cases with one, two and four impurities respectively. By means of the double-time Green's function numerical procedure, it is found that, in the two impurity case, two ferromagnetic impurities prefer to form an effective singlet. While in the four impurity case we obtained that, two nearest-neighbor ferromagnetic domains with contrary spin directions are formed in the antiferromagnetic background, and thus the whole system has the lowest energy.
ANTIFERROMAGNETIC QUANTUM PHASE TRANSITION IN THE QUANTUM PSEUDOGAP PHASE OF CUPRATES
Authors: KWON HYOK-JON
Published: July 2002

We investigate a zero-temperature itinerant antiferromagnetic transition where the fermions possess a d-wave gap. This problem pertains to both the nodal liquid insulating phase and the d-wave superconducting phase of the underdoped cuprates. We find that a non-trivial quantum phase transition exists, and that the quantum critical point is dominated by a long-ranged interaction (|x-y|-2d) of the Néel order parameter, which is induced by the Dirac-like fermions near gap nodes. We formulate a Ginzburg–Landau functional and estimate the critical exponents via the large-n expansion method.
IN SITU ION BEAM ANALYSIS OF CHEMICAL AND PLASMA ETCHING OF Si
Authors: PADMANABHAN KARUR R.
Published: July 2002

The possibility of carrying out in situ ion beam analysis of a gas-solid interface using RBS/Channeling techniques has been investigated using chemical and plasma etching of Si . A specially constructed thin Si window cell is used to initiate chemical etching of Si using Xe F 2. Analysis of etched Si surface using conventional, micro RBS/Channeling and computer simulated channeling spectra indicates a smooth damage free surface with fairly uniform etching. A moderate increase in etching rate and channeling χ min is observed in the presence of the analyzing beam. The results of chemical etching are compared with that due to Ar + and Xe + plasma induced etching of Si . In situ microbeam channeling analysis with CCM (Channeling Contrast Microscopy) of the plasma-etched surface indicates distinct differences in both etching rate and damage profile of Si (100) surface. The etching rate enhancement and damage profile have been explained using conventional TRIM analysis and ion beam surface damage.
How Does Lagrange's Theorem Solve Thermodynamics of a Multispecies Quasiparticle Gas with Mutual Fractional Exclusion Statistics?
Authors: Iguchi Kazumoto
Published: July 2002

Lagrange's theorem for one complex variable functions is generalized to that for multi-complex variable functions, and applied to obtaining thermodynamics and generalized cluster expansions for a multispecies quasiparticle gas with mutual fractional exclusion statistics.
NUCLEATION AND GROWTH OF DIAMOND FILM ON POROUS SILICON SUBSTRATE
Authors: LIAO Y. , FANG R. C. , YE F. , SHAO Q. Y. , WANG G. Z.
Published: July 2002

Nucleation and growth of diamond film on porous silicon are investigated in a hot-filament chemical vapor deposition system. The characters of diamond film are determined by scanning electronic microscopy, Raman spectra and X-ray photoelectron spectroscopy. A nucleation density of 3.6×107 cm -2 is obtained. We find that almost all nuclei occur at the edge of the etched pores. The diamond film directly deposits on porous silicon substrate without the intermediate and no strains are found in the film.
MULTIPLE PHASE TRANSITIONS IN PEROVSKITE STRUCTURE CERAMICS: STRUCTURAL TRANSITIONS
Authors: EAB C. H. , WIWATANAPATAPHEE B. , TANG I. M.
Published: July 2002

A Ginzburg–Landau theory for the multiple structural phase transition observed in the cuprate perovskite structure ceramics is developed. The order parameters Λi for each phase are defined in terms of the deformations which occur in each phase. In terms of the deformation, the expansion of the free energies is to the twelfth order. The theory can account for a second-order tetragonal to orthorhombic-I transition at high temperatures and a first-order orthorhombic-I to orthorhombic-II transition at lower temperatures. The criterion for the existence of a tricritical line is established.
CONCURRENT MAP BUILDING AND LOCALIZATION ON INDOOR DYNAMIC ENVIRONMENTS
Authors: ANDRADE-CETTO JUAN , SANFELIU ALBERTO
Published: July 2002

A system that builds and maintains a dynamic map for a mobile robot is presented. A learning rule associated to each observed landmark is used to compute its robustness. The position of the robot during map construction is estimated by combining sensor readings, motion commands, and the current map state by means of an Extended Kalman Filter. The combination of landmark strength validation and Kalman filtering for map updating and robot position estimation allows for robust learning of moderately dynamic indoor environments.
FRACTAL TRANSITION IN CONTINUOUS RECURRENT NEURAL NETWORKS
Authors: SATO SHOZO , GOHARA KAZUTOSHI
Published: July 2002

A theory for continuous dynamical systems stochastically excited by temporal external inputs has been presented. The theory suggests that the dynamics of continuous-time recurrent neural networks (RNNs) is generally characterized by a set of continuous trajectories with a fractal-like structure in hyper-cylindrical phase space. We refer to this dynamics as the fractal transition. In this paper, three types of numerical experiments are discussed in order to investigate the learning process and noise effects in terms of the fractal transition. First, to analyze how an RNN learns desired input–output transformations, a simple example with a single state was examined in detail. A fractal structure similar to a Cantor set was clearly observed in the learning process. This finding sheds light on the learning of RNNs, i.e. it suggests that the learning is a process of adjusting the fractal dimension. Second, input noise effects on the fractal structure were investigated. The results show that small-scale hierarchical structures are broken by noise. Third, using a network with twenty states, we show that fractal transition is a universal characteristic of RNNs driven by switching inputs.
CHAOTIC RESONANCE — METHODS AND APPLICATIONS FOR ROBUST CLASSIFICATION OF NOISY AND VARIABLE PATTERNS
Authors: KOZMA ROBERT , FREEMAN WALTER J.
Published: July 2002

A fundamental tenet of the theory of deterministic chaos holds that infinitesimal variation in the initial conditions of a network that is operating in the basin of a low-dimensional chaotic attractor causes the various trajectories to diverge from each other quickly. This "sensitivity to initial conditions" might seem to hold promise for signal detection, owing to an implied capacity for distinguishing small differences in patterns. However, this sensitivity is incompatible with pattern classification, because it amplifies irrelevant differences in incomplete patterns belonging to the same class, and it renders the network easily corrupted by noise. Here a theory of stochastic chaos is developed, in which aperiodic outputs with 1/f2 spectra are formed by the interaction of globally connected nodes that are individually governed by point attractors under perturbation by continuous white noise. The interaction leads to a high-dimensional global chaotic attractor that governs the entire array of nodes. An example is our spatially distributed KIII network that is derived from studies of the olfactory system, and that is stabilized by additive noise modeled on biological noise sources. Systematic parameterization of the interaction strengths corresponding to synaptic gains among nodes representing excitatory and inhibitory neuron populations enables the formation of a robust high-dimensional global chaotic attractor. Reinforcement learning from examples of patterns to be classified using habituation and association creates lower dimensional local basins, which form a global attractor landscape with one basin for each class. Thereafter, presentation of incomplete examples of a test pattern leads to confinement of the KIII network in the basin corresponding to that pattern, which constitutes many-to-one generalization. The capture after learning is expressed by a stereotypical spatial pattern of amplitude modulation of a chaotic carrier wave. Sensitivity to initial conditions is no longer an issue. Scaling of the additive noise as a parameter optimizes the classification of data sets in a manner that is comparable to stochastic resonance. The local basins constitute dynamical memories that solve difficult problems in classifying data sets that are not linearly separable. New local basins can be added quickly from very few examples without loss of existing basins. The attractor landscape enables the KIII set to provide an interface between noisy, unconstrained environments and conventional pattern classifiers. Examples given here of its robust performance include fault detection in small machine parts and the classification of spatiotemporal EEG patterns from rabbits trained to discriminate visual stimuli.
SYNCHRONIZATION OF TWO UNCERTAIN CHAOTIC SYSTEMS VIA ADAPTIVE BACKSTEPPING
Authors: WANG C. , GE S. S.
Published: July 2002

In this letter, adaptive synchronization of two uncertain chaotic systems is presented using adaptive backstepping with tuning functions. The master system is any smooth, bounded, linear-in-the-parameters nonlinear chaotic system, while the slave system is a nonlinear chaotic system in the strict-feedback form. Both master and slave systems are with key parameters unknown. Global stability and asymptotic synchronization between the outputs of master and slave systems can be achieved. The proposed approach offers a systematic design procedure for adaptive synchronization of a large class of continuous-time chaotic systems in the chaos research literature. Simulation results are presented to show the effectiveness of the approach.
JULIA AND MANDELBROT SETS OF CHEBYSHEV FAMILIES
Authors: PEHERSTORFER FRANZ , STROH CHRISTOPH
Published: July 2002

We present one-parameter families of rational functions of arbitrary degree d which are globally generalized polynomial-like of degree d and roughly speaking locally quadratic-like everywhere, where the parameter appears not only as a purely multiplicative factor but also in a more complicated nonlinear way. The connectedness locus of these families contains homeomorphic copies of the Mandelbrot set. Main emphasis is put on the explicit construction (and not as usual on the existence only) of the sets on which generalized polynomial-likeness and quadratic-likeness are given as well as on the explicit description of the regions where the homeomorphic copies of the Mandelbrot set are located.
ELIMINATION OF CHAOS IN MULTIMODE, INTRACAVITY-DOUBLED LASERS IN THE PRESENCE OF SPATIAL HOLE-BURNING
Authors: PIETRZYK MONIKA E. , DANAILOV MILTCHO B.
Published: July 2002

In this paper possibilities of a stabilization of large amplitude fluctuations in an intracavity-doubled solid-state laser are studied. The modification of the cross-saturation coefficient by the effect of spatial hole-burning is taken into account. The stabilization of the laser radiation by an increase of the number of modes, as proposed in [James et al., 1990b; Magni et al., 1993], is analyzed. It is found that when the cross-saturation coefficient is modulated by the spatial hole-burning the stabilization is not always possible. We propose a new way of obtaining a stable steady-state configuration based on an increase of the strength of nonlinearity, which leads to a strong cancellation of modes, so that during the evolution all modes, but for a single one, are canceled. Such a steady-state solution is found to be stable with respect to small perturbations.
TIME-DEPENDENT BIFURCATION: A NEW METHOD AND APPLICATIONS
Authors: HUA CUN-CAI , LU QI-SHAO
Published: July 2002

A new qualitative method is presented for studying the bifurcation problems of nonlinear systems with time-dependent parameters. The concept of stability on finite time intervals is introduced and some related stability theorems are established in order to analyze time-dependent bifurcation problems. As some applications of the new method, three different types of delayed bifurcation transitions and jump phenomena of time-dependent Duffing–van der Pol's equation are investigated qualitatively. The bifurcation transition values are predicted by constructing the V-functions or by the linear stability. The sensitivity of motion to the initial values and parameters is also discussed.
BIFURCATIONS OF SOLITARY WAVES AND DOMAIN WALL WAVES FOR KdV-LIKE EQUATION WITH HIGHER ORDER NONLINEARITY
Authors: LIU ZHENGRONG , LI JIBIN
Published: July 2002

Bifurcations of solitary waves and domain wall waves for a KdV-like equation with higher order nonlinearity are studied, by using bifurcation theory of planar dynamical systems. Bifurcation parameter sets are shown. Numbers of solitary waves and domain wall waves are given. Under some parameter conditions, a lot of explicit formulas of solitary wave solutions and domain wall solutions are obtained.
GENERATION OF NONLINEAR CURRENT–VOLTAGE CHARACTERISTICS: A GENERAL METHOD
Authors: COMTE J. C. , MARQUIÉ P.
Published: July 2002

A general method allowing to construct nonlinear resistors with arbitrary current–voltage (I–V) characteristics is proposed. The example of a cubic I–V characteristic is presented showing a perfect agreement between the theoretical desired resistor and its electronic realization based on analog multipliers.
COMBINATORIAL APPROXIMATION BY DEVANEY-CHAOTIC OR PERIODIC VOLUME PRESERVING HOMEOMORPHISMS
Authors: ALPERN STEVE
Published: July 2002

We modify a combinatorial idea of Peter Lax, to uniformly approximate any volume preserving homeomorphism of the closed unit cube In, n≥2, by another one which either: (i) rigidly permutes an infinite family of dyadic cubes of total volume one, or (ii) is chaotic in the sense of Devaney. Our methods apply as well to arbitrary compact manifolds endowed with a nonatomic, locally positive Borel measure.
COMMUNICATIONS USING CASCADE COUPLED PHASE-LOCKED LOOP CHAOS
Authors: KORZINOVA MARINA V. , MATROSOV VALERY V. , SHALFEEV VLADIMIR D.
Published: July 2002

It has been shown that chaotic signal can be obtained from cascade coupled phase-locked loop systems in a broad region of parameter variation. In this paper we demonstrate by computer simulation that the cascade coupled PLLs may be a useful tool for the solution of the problem of synchronization of two PLL systems in the regime of chaotic oscillations (with stabilized average frequency). We give an example of using cascade coupled PLLs for data communication by means of the chaotic signal.
SIGNAL TRANSFER AND STOCHASTIC RESONANCE IN COUPLED NONLINEAR SYSTEMS
Authors: HAUPTMANN C. , KAISER F. , EICHWALD C.
Published: July 2002

A model of coupled nonlinear oscillators is discussed, wherein Langevin-type bistable systems are combined with self-sustained oscillators. An external harmonic signal is coupled in a subthreshold manner into the bistable systems at the initial stage of the signal chain. Signal transfer through the oscillators is studied under the influence of noise. Different noise contributions, including spatially-incoherent and spatially-coherent noise sources are considered. Results reveal a stochastic resonance kind of behavior at different stages of the signal transfer, specifically the harmonic signal is transduced through the whole system of coupled oscillators. The combined action of spatially-incoherent and spatially-coherent noise exhibits constructive as well as destructive influences on signal amplification.
INTERVAL MAPS WITH STRICTLY CONTRACTING PERRON–FROBENIUS OPERATORS
Authors: KELLER GERHARD
Published: July 2002

In this paper we give a computable criterion for a piecewise-expanding interval map T to be mixing, which at the same time not only establishes explicit bounds on the spectral gap of the associated Perron–Frobenius operator acting on the space of functions of bounded variation, but also establishes strict contraction rates for this operator. Of course such a result cannot be completely general, but our procedure covers a number of examples with inf |T′|>2 and the bounds derived for them compare favorably with other estimates found in the literature.
ON THE VARIATIONAL APPROXIMATION OF FREE-DISCONTINUITY PROBLEMS IN THE VECTORIAL CASE
Authors: FOCARDI M.
Published: July 2002

We provide a variational approximation for quasiconvex energies defined on vector valued special functions with bounded variation. We extend the Ambrosio–Tortorelli's construction to the vectorial case.
SYMMETRY RESTORATION IN THE SUPERSTRING THEORY
Authors: POLLOCK M. D.
Published: July 2002

The grand unified gauge group G 6≡ SU (3) C × SU (3) L × SU (3) R , which results from compactification of the heterotic superstring onto a three-generation Calabi–Yau space as a maximal subgroup of E 6, contains two superfields, whose scalar components are the conjugates neutrino [Formula: see text] and the neutral Higgs N, which are singlets of the standard-model gauge group G 4≡ SU (3) C × SU (2) L × U (1) Y , and which therefore break G 6to G 4 when they acquire non-vanishing vacuum expectative values. Here, we show how this process can be implemented in two steps when the scalar potential V(ϕi) is chosen along a non-D-flat direction, using the "superconducting" model due to Mohapatra and Senjanović, in which one of two scalar fields remains in the asymmetric state up to a temperature T0~ 1017 GeV , above which the kinetic energy exceeds the potential drop, forcing restoration of the symmetry below the compactification scale T c ≈ 1017 GeV . This implies that [Formula: see text] initially, but at low temperatures T ≪ M w , we find that [Formula: see text], thus avoiding the problems associated with large intermediate scales M I ≳ 109 GeV while keeping the Higgs mixing term ~ NH1H2 at the right level. A discrete gauge symmetry can prevent the proton from decaying too rapidly.
RELATIVISTIC MEAN FIELD THEORETICAL FOUNDATION OF THE DROPLET MODEL FOR NUCLEI
Authors: GAO CHUN-YUAN , ZHANG QI-REN
Published: July 2002

The binding energies per-nucleon for 1654 nuclei, whose mass numbers range from 16 to 263 and charge numbers range from 8 to 106, are calculated by the relativistic mean field theory, with finite nucleon size effect being taken into account. The calculated energy surface goes through the middle of experimental points, and the root mean square deviation for the binding energies per-nucleon is 0.08163 MeV. The numerical results may be well simulated by a droplet model type mass formula. The droplet model is therefore put on the relativistic mean field theoretical foundations.
TRANSVERSE RESONANT OSCILLATIONS IN ACOUSTIC DUCTS
Authors: VAINSHTEIN P.
Published: July 2002

A theoretical study is made of the flow induced by a piston, performing rotational sinusoidal vibrations in a uniform two-dimensional planar duct. A frequency of the forced vibrations is close to a cut-off frequency. It is shown that exactly at a cut-off frequency the steady-state response represents a transverse periodic shock wave, propagating between duct walls and decaying algebraically in the far field.
REACTION OF CO2 WITH MgO(100) SURFACES
Authors: CARRIER X. , DOYLE C. S. , KENDELEWICZ T. , BROWN G. E.
Published: July 2002

Synchrotron-based photoemission spectroscopy (C 1s and O 1s regions) as well as C K-edge NEXAFS spectroscopy have been used to investigate the formation of carbonate species on the surface of MgO(100) after exposure to CO 2 at pressures ranging from 0.8 to 260 Torr. These results are tentatively compared with a two-stage model for the reaction of H 2 O on MgO(100) [Liu et al., Surf. Sci.412/413, 287 (1998)]. At p( CO 2) values below a threshold pressure (predicted to be in the range of 10-9–10-6 Torr), the reaction of CO 2 with MgO(100) is fairly limited and CO 2 is assumed to react with defect sites only. At pressures ≥ 0.8 Torr, CO 2 reacts with terrace sites, resulting in extensive formation of [Formula: see text] groups on the MgO(100) surface. However, carbonate formed at "high" pressures ( P CO 2 ≥ 0.8 Torr) begins to desorb at the low pressure of the analysis chamber (10-11 Torr), which is consistent with equilibrium thermodynamic predictions of the "threshold" pressure for the reaction MgO + CO 2= MgCO 3. Results from polarization-dependent C K-edge NEXAFS spectroscopy suggest that the carbonate molecules formed on the surface are structurally disordered. The chemical nature of adventitious carbon formed on the MgO(100) surface was also invesgtigated, and is clearly different from [Formula: see text].
TREATMENT OF SUBUNGUAL GLOMUS TUMOUR
Authors: Takata Haruhiko , Ikuta Yoshikazu , Ishida Osamu , Kimori Kenji
Published: July 2002

We reviewed 30 patients with subungual glomus tumours of the hand operated on between 1964 and 1997. Seven patients were male and 23 were female. Their age ranged from 16 to 78 years. A transungual approach was selected in 27 patients, and a periungual approach in three. Pre-operative pain subsided in all of the patients, but recurrence of the pain was observed in nine. Nail deformities were observed in nine patients before surgery. After surgery, it disappeared in three patients, persisted in six, and new deformities developed in five. To avoid recurrence of pain, it is important that the accurate pre-operative localisation of the tumour and a complete extirpation should be performed. To avoid nail deformity, it is better to apply a periungual approach for tumours developing in the peripheral region, and a transungual approach followed by meticulous repair of the nail bed for tumours developing in the central region.
COHERENCE MAINTAINANCE IN COOPERATIVE INFORMATION SYSTEMS: THE ACCESS KEY WAREHOUSE APPROACH
Authors: ARCIERI FRANCO , CAPPADOZZI ELETTRA , NAGGAR PAOLO , NARDELLI ENRICO , TALAMO MAURIZIO
Published: July 2002

In this paper, we present and discuss a novel architectural approach supporting the integration among legacy information systems of autonomous organizations. It is based on the use of a data warehouse in a new conceptual role. Namely, we propose to use it, during the design and implementation phases of a cooperative information system, as a tool supporting the coherence maintenance of the underlying databases and the efficient management of accesses to them. Our approach is rooted in the SICC project for cadastral data exchange among Italian Municipalities, Ministry of Finance, Notaries, and Certified Land Surveyors. Research results reported here are an abstraction of solutions introduced in the SICC project and validated through the development of various inter-organization cooperative information systems, managed by the "Coordinamento dei Progetti Intersettoriali" of AIPA, the Italian Authority for Information Technology in Public Administration.
STOCK EVALUATION USING FUZZY LOGIC
Authors: DOURRA HUSSEIN , SIY PEPE
Published: July 2002

We use fuzzy logic engineering tools to detect human behavior in the finance arena, specifically in the technical analysis field. Since technical analysis theory consists of indicators used by experts to evaluate stock prices, the new proposed method maps these indicators into new inputs that can be fed into a fuzzy logic system. This system can create an optimum computerized model to evaluate stock price movement. This method relies on human psychology to predict human behavior when certain price movements or certain price formations occur. The success of the system is measured by comparing system output versus stock price movement. The new stock evaluation method is proven to exceed market performance and it can be an excellent tool in the technical analysis field. The flexibility of the system is also demonstrated.
Managing Risk by Using Derivatives: The Case of Hong Kong Firms
Authors: Yu Eden S. H. , Chin Ivan Chan Hung , Hang Henry Fu Yiu , Wai George Lo Chi
Published: July 2002

Hong Kong has been very active in developing new financial products. This paper examines how firms in Hong Kong have managed risks by using derivatives. We conducted a survey to find out what kind of and to what extent financial engineering tools are used. Our survey reveals that derivatives are widely used to reduce risks. Moreover, most companies take risk measurement prior to including derivatives in the portfolios. The value-at-risk model is the most widely used risk management technique, followed by scenario analysis. In addition, we compare these survey results with the recent results for firms in Shanghai.
ON MARKOV CHAINS AND THE SPECTRA OF THE CORRESPONDING FROBENIUS–PERRON OPERATORS
Authors: GAYER TOBIAS
Published: July 2002

The paper presents some notes on the theoretical background of recent computational approaches to identify the dynamical behavior of Markov chains by solving an eigenvalue problem of the Frobenius–Perron operator. We show that for each subset of its peripheral spectrum, the corresponding generalized eigenspace and the geometric eigenspace coincide. Furthermore, the peripheral spectrum forms a cyclic set. The elements of this set stand in a one-to-one relationship to cyclic and invariant behavior of the underlying stochastic process. If the dynamics of the chain is perturbed continuously, invariant sets of the unperturbed chain possibly merge and become almost invariant. We give a precise continuity condition under which the merging of two invariant sets and the appearance of almost invariant sets can be observed and follow how the corresponding eigenmeasure leaves the eigenspace associated to 1. Finally, as an example we present the appearance of almost invariance for a Markov chain on a compact interval.