bluuebunny/crossref_metadata_2025 huggingface dataset:
J/ψ DECAYS AND η-η′-ι MIXING
Authors: KITAMURA ICHIJIRO , MORISITA NORIKAZU , TESHIMA TADAYUKI
Published: November 2004

The mass region near η(1440) has more than one resonance, and two resonances with M≈1420 MeV and M≈1490 MeV are shown to give a better description of the recent experimental data. We investigate whether η(1420) or η(1490) is the glueball, if it exists, and which of them is the isospin 0 partner of the radially excited state η(1295) expected to exist near the 1500–1600 MeV region. We study the J/ψ→VP and Pγ decays, using the new data of 1992, to estimate the mixing among (η, η′, ι), where ι refers to the glueball, and obtain the result that the N component in ι is larger than the S component. Comparing the N and S components in ι with the N and S components in η(1420) and η(1490) obtained from their decaying pattern, we conjecture that the low mass state η(1420) is the glueball and the high mass state η(1490) is the radial excitation state. We discuss the relation between the mass formulae for the pseudoscalar mesons and the mixing among (η, η′, ι) obtained considering the chiral perturbation theory and the chiral U(3) × U(3) symmetry formulation.
A GENERALIZATION OF THE JORDAN-SCHWINGER MAP: THE CLASSICAL VERSION AND ITS q DEFORMATION
Authors: MAN’KO V.I. , MARMO G. , VITALE P. , ZACCARIA F.
Published: November 2004

For all three-dimensional Lie algebras the construction of generators in terms of functions on four-dimensional real phase space is given with a realization of the Lie product in terms of Poisson brackets. This is the classical Jordan-Schwinger map, which is also given for the deformed algebras [Formula: see text], ℰq(2) and ℋq(1). The algebra [Formula: see text] is discussed in the same context.
2D QUANTUM GRAVITY COUPLED TO RENORMALIZABLE MATTER FIELDS
Authors: AMBJØRN JAN , GHOROKU KAZUO
Published: November 2004

We consider two-dimensional quantum gravity coupled to matter fields which are renormalizable but not conformally invariant. Questions concerning the β function and the effective action are addressed, and the effective action and the dressed renormalization group equations are determined for various matter potentials.
STRONG COULOMB COUPLING IN RELATIVISTIC QUANTUM CONSTRAINT DYNAMICS
Authors: BAWIN M. , CUGNON J. , SAZDJIAN H.
Published: November 2004

We study, in the framework of relativistic quantum constraint dynamics, the bound state problem of two oppositely charged spin 1/2 particles, with masses m1 and m2, in mutual electromagnetic interaction. We search for the critical value of the coupling constant α for which the bound state energy reaches the lower continuum, thus indicating the instability of the heavier particle or of the strongly coupled QED vacuum in the equal mass case. Two different choices of the electromagnetic potential are considered, corresponding to different extensions of the substitution rule into the nonperturbative region of α: (i) the Todorov potential, already introduced in the quasipotential approach and used by Crater and Van Alstine in Constraint Dynamics; (ii) a second potential (potential II), characterized by a regular behavior at short distances. For the Todorov potential we find that for m2>m1 there is always a critical value αc of α, depending on m2/m1, for which instability occurs. In the equal mass case, instability is reached at αc=1/2 with a vanishing value of the cutoff radius, generally needed for this potential at short distances. For potential II, on the other hand, we find that instability occurs only for m2>2.16 m1.
TOPOLOGICAL STUDY OF GLOBAL QUANTIZATION IN NON-ABELIAN GAUGE THEORIES AND THE OPEN UNIVERSE
Authors: ZHANG HUAZHONG
Published: November 2004

We study some topological aspects of non-Abelian gauge theories intimately connected with the Lie algebras of the gauge groups and the homotopy theory in the generalized gauge orbit space. The physics connection with the nonperturbative solution to the strong CP problem by magnetic monopoles and the quantization rule for the effective vacuum angle as originally proposed by the author are also discussed. In addition, some relevant topological formulas are given and discussed. We emphasize that a result7 from their physics application is that the usual gauge orbit space on the compactified space may contain at most a Z2 monopole structure in the SP (2N)(N= rank ) gauge theories; such a Z2 structure may induce spontaneous CP violations in SP (2N) gauge theories, as was noted. Some relevance to the open universe is discussed too. It is expected from our results that the open universe in the case of a nonvanishing θ can also be regarded as a quantum effect of the global quantization in the gauge orbit space. We expect that our results will be useful for other studies of non-Abelian gauge theories in general. Some remarks are also given related to our global quantization and the gauge theories in generalized gauge orbit space.
BRST ANALYSIS OF N=2 SUPERCONFORMAL MINIMAL UNITARY MODELS IN COULOMB GAS FORMALISM
Authors: SUGIYAMA KATSUYUKI
Published: November 2004

We perform a BRST analysis of the N=2 superconformal minimal unitary models. A bosonic as well as fermionic BRST operators are used to construct irreducible representations of the N=2 superconformal algebra on the Fock space as BRST cohomology classes of the BRST operators. Also a character formula is rederived by using the BRST analysis.
SPIN DYNAMICS IN THE NORMAL STATE OF HIGH-Tc SUPERCONDUCTORS
Authors: SI QIMIAO
Published: November 2004

We summarize our recent theoretical studies on the spin dynamics in the normal state of the metallic cuprates. The contrasting wave vector dependence of the dynamical spin structure factor S (q, ω) in LaSrCuO and YBaCuO systems are attributed to the differences in the fermiology, in conjunction with strong Coulomb correlations. These effects are found to account also for the anomalous temperature and frequency dependence of S (q, ω). We conclude that the low energy spin dynamics of the metallic cuprates are described in terms of correlated quasiparticles with a Luttinger Fermi surface and a non-zero antiferromagnetic exchange interaction.
NONLINEAR QUANTUM BEAT SPECTROSCOPY IN SEMICONDUCTORS
Authors: PANTKE KARL-HEINZ , HVAM JØRN M.
Published: November 2004

We review quantum beats from extended electronic states in bulk semiconductors and multiple quantum well structures obtained by nonlinear spectroscopy. The nonlinear methods are degenerate four-wave mixing, photon echo and nonlinear transmission. The role of the spectral resolution of the nonlinear signal emitted from a four-wave mixing process is discussed in detail. Results obtained by linear methods like fluorescence or transmission are briefly discussed.
ON THE NATURE OF FLUORESCENT SPECTRUM OF A TWO ATOM DICKE MODEL IN A NARROW BANDWIDTH SQUEEZED BATH
Authors: JOSHI AMITABH , PURI R. R.
Published: November 2004

We discuss the spectrum of resonance fluorescence from a system of two identical coherently driven two-level atoms interacting with a finite bandwidth squeezed bath, including the atomic dipole-dipole interaction between the atoms. The characteristics of the spectral features are studied by solving the master equation analytically in the limit of strong driving field. The comparison of these features with respect to an ordinary bath as well as broadband squeezed bath are also presented.
EDGE WAVES and CHIRAL BOSONIZATION
Authors: Stone Michael
Published: November 2004

The incompressible quantum Hall states of a two-dimensional electron liquid have gapless excitations at their edges. These ripples in the electron charge profile are physical realizations of chiral bosons. I review this Bose-Fermi correspondence in the simplest case of a single filled Landau level.
EXTENSION OF THE YAKHOT–ORSZAG RENORMALIZATION GROUP-BASED CLOSURE SCHEME TO ISOTROPIC AND ANISOTROPIC TWO-DIMENSIONAL TURBULENCE
Authors: OLLA PIERO
Published: November 2004

The renormalization group based closure developed by Yakhot and Orszag for the analysis of three-dimensional turbulence is extended to the two-dimensional case. The logarithmically corrected Ek ∝ ( log k/k1)–1/3 k–3 energy spectrum of the enstrophy inertial range and the k−5/3 spectrum of the energy range are derived self-consistently by the method. The values for the Kolmogorov constants C′ = 2.29 in the enstrophy range and C = 6.45 in the energy range are obtained without the need of adjustable parameters. These solutions are proven to be linearly stable against anisotropic perturbations and the decay of anisotropy at small scales given anisotropic large scales is shown to be ∝ ( In k/k1)−1/12 in the enstrophy range and ∝ k−1/6 in the energy range. The difficulty in observing a k−3 spectrum in two-dimensional turbulence has a counterpart in the renormalization group closure, in the fact that such a spectrum would require an enstrophy input from the stochastic force exceeding the contribution of the flux from larger scales. Application of the method to the problem of the passive scalar leads to Prandtl numbers equal to one and Batchelor constants equal to the Kolmogorov constant of the respective range. Calculation of the two-dimensional skewness s2 = <∂xvx (∂xq)2>/[<(∂xvx)2>1/2<(∂xq)2>] leads to the result s2 ≃ −.265 in the enstrophy range.
INTERACTION OF ALKALI METALS WITH SOLID SURFACES STUDIED BY LOW-ENERGY D+ SCATTERING
Authors: SOUDA R.
Published: November 2004

The study of alkali-metal adsorption on metal and semiconductor surfaces has been a favored topic of surface science. This is motivated by a number of interesting physical effects, such as charge transfer, work function changes, and alteration of surface reactivity. Despite considerable research efforts, however, there has still been significant controversies about most of these properties.

In this paper, a review is presented concerning alkali–metal adsorption on well-defined transition-metal and semiconductor surfaces, with particular emphasis on the bond-nature analysis using low-energy D + scattering. The analysis based on resonance neutralization of the D + ions associated with the 1s hole diffusion into the band reveals that Na, K, and Cs adatoms have significant covalency on the transition metal surfaces while those except for Na are ionically adsorbed on the semiconductor surfaces in a small coverage regime (< 1.7 × 1014 adatoms/cm 2). The charge state of Na is rather critical because of the larger ionization energy than the others. The other examples are concerned with the analyses of the interaction of these alkali–metal adatoms with electronegative species such as oxygen and halogens on the metal and semiconductor surfaces.
HOPPING TRANSPORT AND QUANTUM HALL EFFECT: ABSORPTION OF SURFACE ACOUSTIC WAVES
Authors: Aleiner I.L. , Shklovskii B.I.
Published: November 2004

New theory of the width of the peaks of the diagonal conductivity in the quantum Hall effect suggested recently by Polyakov and Shklovskii is extended to describe the peak widths of attenuation of the surface acoustic waves (SAW). In contrast to electromagnetic waves, wavelength of SAW can be smaller than the relevant localization length. This leads to a drastic increase of the peaks widths. The latter are shown to grow as (Ts(ω)/T1)0.4 where the effective temperature Ts is about 400ħω for GaAs.
PERCOLATIVE ASPECTS OF VISCOUS FLOW NEAR THE GLASS TRANSITION
Authors: HUNT ALLEN
Published: November 2004

Jumps in e.g.“equilibrium” specific heats, ∆C at the glass “transition”, Tg are kinetic. The upward curvature of log viscosity, η, vs 1/T supposedly indicates a phase transition at T0<Tg because the functional form fitting data over the largest temperature range diverges at (an inaccessible) T0. But the strongest curvature of η is near Tc, often 50K above Tg; it marks a cross-over from diffusive (T>Tc) (treated in effective-medium theories) to percolative transport (T<Tc). The pressure, (P), dependence of Tg, correlations of Tg with T0 and the melting temperature, Tm, (mixed) applicability of Ehrenfest theorems to dTg/dP, decoupling of mechanical and dielectric relaxation at Tc (measured by Rd, the ratio of mechanical and dielectric relaxation times), correlation of non-exponentiality in dielectric relaxation with Rd, dependence of Tg on system size, relative rates for shear and bulk moduli, and shapes of dielectric and specific heat relaxations can be described. Possibly the correlation of the Kauzmann temperature, TK, with T0 is also explicable using percolation. TK marks coincidence of extrapolated “configurational” entropies of super-cooled liquids with corresponding crystals. The physical basis for these results in a relevance of short-range inhomogeneities (which “average out” over large distances) removes a need to consider an underlying phase transition.
THE HOPPING CONDUCTION OF NEUTRON TRANSMUTED GERMANIUM
Authors: ZABRODSKII A.G. , ANDREEV A.G.
Published: November 2004

An investigation was made of a batch of samples of neutron transmutation-doped (NTD) Ge:Ga with the degree of compensation K=0.3 and the concentration of the main impurity (Ga) from N=3.6 · 1014cm−3 to Nc=2.5 · 1017cm−3, corresponding to the MI transition. The following were studied: the parameters of NTD Ge:Ga, the temperature dependence of hopping transport, the ɛ3 region of the nearest neighbor hopping (NNH), the saturation of NNH, variable range hopping (VRH) and the Coulomb gap.
HYDROGEN IN CRYSTALLINE SEMICONDUCTORS: PART I—SILICON
Authors: PEARTON S.J.
Published: November 2004

Hydrogen plays an important role in the properties of Si because of its ability to passivate the electrical activity of shallow dopants and deep level impurities. This passivation can occur during virtually every stage of crystal growth, device fabrication or device operation due to the rapid diffusivity of hydrogen at low temperatures and the fact that it is a component of virtually every gas or liquid that comes in contact with Si. We review the ability of hydrogen to form neutral complexes with dopants and impurities, give examples of hydrogen diffusion profiles in doped and undoped Si, and mention the role of hydrogen during chemical vapor deposition and molecular beam epitaxy of Si.
CORRELATED MEAN FIELD ANSATZ FOR THE KONDO NECKLACE
Authors: KEE H.Y. , FAZEKAS P.
Published: November 2004

We study the ground state phase diagram of the pseudospin model introduced by Doniach to describe the essential physics of Kondo lattices. We use variational trial states which augment the usual mean-field solution by incorporating various intersite correlations. A composite spin correlation describing the antiparallel alignment of fluctuating triplets is found to be particularly favorable for large Kondo couplings. With this trial state, the magnetic-to-Kondo transition is suppressed and the strong coupling ground state is ordered with strongly reduced moments. The relevance of the findings is discussed.
NUMERICAL SIMULATION OF NEURAL NETWORKS WITH TRANSLATION AND ROTATION INVARIANT PATTERN RECOGNITION
Authors: ANTONUCCI M. , TIROZZI B. , YARUNIN N.D. , DOTSENKO V.S.
Published: November 2004

A Hopfield-like network modified for translation and rotation invariant pattern recognition is studied on a computer. The neural firing thresholds θ are used as additional degrees of freedom. The phase diagram in the space of parameters (T, θ) is obtained both for the translation and the rotation.
MICROSCOPIC MODEL OF SUPERFLUID HELIUM-4
Authors: MARQUES G.C.
Published: November 2004

To understand the properties of superfluid Helium-4 we propose a microscopic model for the description of this imperfect boson gas at very low temperatures. This microscopic theory contains only two parameters that are inferred from the He-He interaction potential. The understanding of the properties of Helium-4 in the super-fluid phase is based on Bose-Einstein condensation and for its description we use field theory at finite temperatures. We get a large number of characteristic features of superfluidity. Among these features we get phonon and roton spectrum, the two-fluid component description and London’s relation. We have also made predictions for twelve physically relevant quantities for He-4 below the λ-point. The predictions of the model were made by using the loop expansion in field theory. We find that our predictions are in reasonable agreement with the experimental results.
IMPROVEMENT TO RANDOM PHASE APPROXIMATION IN THEORY OF STRONGLY CORRELATED ELECTRON SYSTEMS
Authors: IZYUMOV YU.A. , HENDERSON J.A.
Published: November 2004

We include an additional diagram in the bare electron-electron vertex within the generalised random phase approximation (GRPA) for the t-J model. The equation for the effective electron-electron vertex becomes more complicated but is solved exactly for the simple cubic lattice. The dynamical magnetic susceptibility obtained is the same as in GRPA but with all quantities renormalised. Instability of the paramagnetic phase with respect to the formation of ferromagnetic or antiferromagnetic ordering is studied. Formulae for Curie and Neel temperatures are obtained. The additional diagram leads to an extension of the antiferromagnetic region and a reduction in the ferromagnetic region.
SPIN AND CHARGE BIPOLARON KINETICS OF HIGH-Tc SUPERCONDUCTORS
Authors: ALEXANDROV A.S. , MOTT N.F.
Published: November 2004

We extend the BSC theory to the strong electron-phonon (magnon) coupling limit. We show that the formation of small polarons and bipolarons provides a number of new physical phenomena both in the normal and superconducting states and explains low-energy physics of high-Tc superconductors. Both lattice and spin (bi)polarons are discussed. A highly nonadiabatic motion of bipolarons leads to a unique physical nature of (bi)polaronic superconductivity, making it totally different from that of the BCS one, including its wellknown strong-coupling generalization. The maximum attainable Tc is estimated to be in the region of the transition from the Fermi-liquid to a charged Bose-liquid. Some evidence for 2e bosons is given from NMR, neutron scattering, near-infrared absorption, Hall effect, resistivity, thermal conductivity, and critical magnetic fields of high-Tc oxides. An infinite thermal conductivity of two-dimensional charged bosons is predicted below Tc. The insulator-metal transition and ARPES in copper oxides are also discussed. The proposed theory is not restricted by low dimensionality and might be applied to cubic oxides like BaPbBiO and to alkali-doped C 60.
FOCUSING OF QUASI–TRANSVERSE MODES IN ZINC AT ULTRASONIC FREQUENCIES
Authors: KIM KWANG YUL , EVERY ARTHUR. G. , SACHSE WOLFGANG
Published: November 2004

The intense focusing of quasi-transverse (QT) modes along the symmetry axis of zinc is observed by various methods at ultrasonic frequencies. The focusing is associated with a conical point on the QT sheet of the ray surface, and thereby the phenomenon of external conical refraction. The observations have been made first, with pointlike longitudinal (L) and shear (S) piezoelectric transducers acting as acoustic source and detector; second, with a breaking capillary source with Heaviside time-dependence and a capacitive displacement detector at epicenter; and third, using a laser source and piezoelectric detector. The amplitudes of the signals observed by the piezoelectric sources and detectors in both time and frequency domains show intense focusing in the symmetry direction [0001], side-lobed by diffraction fringes caused by the interferences between collinear rays associated with different wave vectors k. A broadband capacitive displacement signal shows a very sharp deep minimum associated with the arrival of the conical rays, being consistent with the calculation of the dynamic Green's function and the theory of phonon focusing for the medium.
THE NONLINEAR DYNAMICS OF A LINEAR CLASSICAL OSCILLATOR COUPLED TO A MACROSCOPIC QUANTUM OBJECT
Authors: RALPH J. F. , SPILLER T. P. , CLARK T. D. , PRANCE R. J. , PRANCE H.
Published: November 2004

In this paper we will discuss a model for the behavior of an rf-SQUID magnetometer, which consists of a macroscopic quantum object which is reactively coupled to a linear classical oscillator. We demonstrate that the coupling between the quantum object and the classical oscillator can lead to manifestly nonlinear behavior in the otherwise linear oscillator; including multi-periodic and chaotic solutions.
VALENCE-FLUCTUATION MECHANISM FOR CUPRATE SUPERCONDUCTIVITY
Authors: BRANDOW B. H.
Published: November 2004

We explore the concept that the above-T c state is a normal Fermi liquid with strong correlations of the type found in valence-fluctuation and heavy-fermion materials. Experimental evidence and theoretical arguments for this phase are presented. Using an Anderson lattice model Hamiltonian, and a variational many-body formalism, the finite-U mechanism for s-like (full point-group symmetry) pairing is examined in detail. At the mean field or (1/N)0 level of approximation, the pairing tendency is strongly opposed by a magnetic tendency arising from a Gutzwiller version of hybridization renormalization. Pairing does not seem possible for realistic Hamiltonian parameters. This finite-U treatment has, however, now been extended to the (1/N)1 level of approximation. The lattice aspect is found to play a major and unexpected role here, leading to strong suppression of the magnetic tendency. This refined treatment is now found to provide adequate pairing attraction, for reasonable Hamiltonian parameters. Superconductivity is found only when the charge transfer energy Δ CT is quite large, Δ CT ≳ U, but there is evidence that Δ CT is indeed of this magnitude in the cuprate materials. Adequate band narrowing (mass enhancement or heaviness) and a very short coherence length are also obtained, in reasonable agreement with experiment. The quasiparticle interaction at the Fermi surface is strongly repulsive. This provides a reasonable source for the large and linear resistivity, as well as for other aspects of marginal-Fermi-liquid phenomenology. Evidence is found for a strong reduction of T c due to pair-breaking by the quasiparticle scattering. The main (fully self-consistent) calculations assume in-plane isotropy. However, a simplified calculation with a more realistic (anisotropic) band structure for the CuO 2 plane is found to provide a highly anisotropic gap, which may or may not have nodes. There is considerable evidence for such types of gap structure. Because a connection is found here between anomalously short coherence length and anomalously high resistivity, we suggest that this mechanism is also operating within other families of "exotic" superconductors.
THEORETICAL ANALYSIS OF FIELD-INDUCED STRUCTURES IN E.R. AND M.R. FLUIDS
Authors: BOSSIS G. , CLERCX H. , GRASSELLI Y. , LEMAIRE E.
Published: November 2004

The rheological properties of E.R. and M.R. suspensions are determined by the strength of the structure built under the application of an electric (respectively magnetic) field. We present a general multipolar method which allows us to obtain the stress-strain curve for any sheared lattice. This is applied to infinite periodic chains of spheres arranged on three different lattices: simple cubic, simple hexagonal and body centered tetragonal. The predicted yield stresses and shear moduli are compared to the predictions of simpler models involving interactions between two or three particles. The field induced structures experimentally observed show that the chains of spheres aggregate into thick columns; we present a model which allows us to calculate the diameter of these aggregates, at least for M.R. fluids, on the basis of a minimization of the free energy.
THE EVOLUTION OF FIELD-INDUCED STRUCTURE OF CONFINED FERROFLUID EMULSIONS
Authors: MOU T. , FLORES G. A. , LIU J. , BIBETTE J. , RICHARD J.
Published: November 2004

We report a real-time study of the evolution of the structure of confined ferrofluid emulsions during the "liquid–solid" phase transition. A monodisperse oil-in-water ferrofluid emulsion is used. The structure evolution of the emulsion after rapidly applying a magnetic field is probed by the static light scattering. The scattering pattern exhibits pronounced rings reflecting the formation of chains and their coalescence to columns or even "worm" structures. The scattering ring is found to decrease in size and brighten in intensity with time. To monitor the structure evolution in time, both the ring peak position in scattering wavevector, q max , and the peak intensity, I max , are measured as a function of time. Both q max and I max saturate in less than 0.5 seconds after applying a magnetic field. At a constant cell thickness of 25 µm, the evolution of structure is essentially independent of volume fraction ranging from 0.015 to 0.13. In addition, a very good scaling is found in the scattered light intensity as a function of the scattering wavevector.
SPECTRUM OF LOW-LYING EXCITATIONS IN A SUPERSYMMETRIC EXTENDED HUBBARD MODEL
Authors: EßLER FABIAN H.L. , KOREPIN VLADIMIR E.
Published: November 2004

We continue the study of the u(2|2)-supersymmetric extension of the Hubbard model in one dimension. We determine the excitation spectrum at zero temperature even in the sectors where the ground states are u(2|2)-descendants of Bethe states. The excitations include spinons, holons, electrons, localons (local electron pairs, moving coherently through the lattice) and their bound states. The spectra are found to be very different for repulsive and attractive on-site interaction. We also study the thermodynamics of the model.
EXACT STEADY STATES OF ASYMMETRIC DIFFUSION AND TWO-SPECIES ANNIHILATION WITH BACK REACTION FROM THE GROUND STATE OF QUANTUM SPIN MODELS
Authors: ALCARAZ FRANCISCO C.
Published: November 2004

We calculated the exact probability distribution of the equilibrium state of some dynamical models in d-dimensional hypercubic lattices (d≥1). In these models we have asymmetric diffusion or two-species annihilation with back reaction A+B↔Ø. Our results are derived by exploring the relationship between the master equation and the Hamiltonian of quantum spins. The models we study are related to the spin-S Heisenberg model.
CONTROL OF A DOUBLE IMPACTING MECHANICAL OSCILLATOR USING DISPLACEMENT FEEDBACK
Authors: GUTIÉRREZ E. , ARROWSMITH D. K.
Published: November 2004

A model which allows a double impacting regime for a particle undergoing simple harmonic motion is considered in some detail. The behavior of the particle in the weak spring limit is considered. Symmetries of the motion are found and the extent of the resonant dynamical behavior is considered. Control equations are developed and strategies are described for both the preservation and the annihilation of experimental and analytical resonant periodic orbits.
ONE-DIMENSIONAL r=2 CELLULAR AUTOMATA WITH MEMORY
Authors: ALONSO-SANZ RAMÓN
Published: November 2004

Standard Cellular Automata (CA) are ahistoric (memoryless): i.e. the new state of a cell depends on the neighborhood configuration only at the preceding time step. This article introduces an extension to the standard framework of CA by considering automata implementing memory capabilities. While the update rules of the CA remains the same, each site remembers a weighted mean of all its past states, with a decreasing weight of states farther in the past. The historic weighting is defined by a geometric series of coefficients based on a memory factor (α). This paper considers the time evolution of one-dimensional range-two CA with memory.
COEXISTENCE OF LOCALIZED STRUCTURES AND PATTERNS IN FARADAY INSTABILITY FOR HIGH DISSIPATIVE FLUIDS
Authors: CABEZA CECILIA , NEGREIRA CARLOS , GIBIAT VINCENT
Published: November 2004

We present an experimental study of the generation of strongly localized structures that propagate on the surface of a dissipative fluid. We excited a layer of fluid with a vertical periodic acceleration field, and a parametric instability occurs when a certain threshold value is achieved. This process is known as Faraday Instability and the temporal evolution of the system obeys a period-doubling route. For a highly dissipative fluid we observed two new interesting phenomena: the generation of high spatially localized structures which propagate on top of the stripes of stationary pattern, and a periodic window which occurs after the system reached spatiotemporal chaos.
CHAOTIC BEHAVIOR AND SUBHARMONIC BIFURCATIONS FOR A ROTATING PENDULUM EQUATION
Authors: CHEN LIJUAN , LI JIBIN
Published: November 2004

Chaotic behavior for a periodically forced system is considered. Under certain parameter conditions, the fact that some combination-type of chaotic motions and all possible types of subharmonic solutions occur simultaneously can be proved. The dynamics of stochastic and resonant layer have been discussed.
EXPLOITING THE ATTRACTOR STRUCTURE FOR CHAOS FEEDBACK CONTROL: THE DUFFING OSCILLATOR
Authors: ALVAREZ-RAMIREZ JOSE , ESPINOSA-PAREDES GILBERTO
Published: November 2004

Departing from the OGY method reported in 1990, many methodologies for chaos control have been proposed. A major criticism is that most of them are merely straightforward applications of methodologies borrowed from feedback control theory. In fact, an authentic chaos control methodology should rely on the underlying structure (e.g. topology, dynamics, etc.) of chaotic behavior in order to provide simple and successful feedback control algorithms. This brief paper focuses on this objective; namely, to exploit chaos structure to design feedback controllers aimed to eliminate chaos. The well-known Duffing oscillator is used to show how the mechanisms leading to chaotic behavior can be destroyed by means of a simple feedback control. Specifically, it is shown that injected damping, via feedback control, is able to eliminate the transverse homoclinic orbit responsible for the chaotic behavior of the Duffing oscillator.
BASINS OF ATTRACTION FOR CASCADING MAPS
Authors: BOCZKO ERIK , YOUNG TODD
Published: November 2004

We study a finite uni-directional array of "cascading" or "threshold coupled" chaotic maps. We describe some of the attractors for such systems and prove general results about their basins of attraction. In particular, we show that the basins of attraction have infinitely many path components. We show that these components always accumulate at the corners of the domain of the system. For all threshold parameters above a certain value, we show that they accumulate at a Cantor set in the interior of the domain. For certain ranges of the threshold, we prove that the system has many attractors.
STABILITY OF MULTI-LAYER CELLULAR NEURAL/NONLINEAR NETWORKS
Authors: TÖRÖK LEVENTE , ROSKA TAMÁS
Published: November 2004

We have found a formalism that lets us present generalizations of several stability theorems (see Chua & Roska, 1990; Chua & Wu, 1992; Gilli, 1993; Forti, 2002] on Multi-Layer Cellular Neural/Nonlinear Networks (MLCNN) formerly claimed for Single-Layer Cellular Neural/Nonlinear Networks (CNN). The theorems were selected with special regard to usefulness in engineering applications. Hence, in contrast to many works considering stability on recurrent neural networks, the criteria of the new theorems have clear indications that are easy to verify directly on the template values. Proofs of six new theorems on 2-Layer CNNs (2LCNN) related to symmetric, τ-symmetric, nonsymmetric, τ-nonsymmetric, and sign-symmetric cases are given. Furthermore, a theorem with a proof on a MLCNN with arbitrary template size and arbitrary layer number in relation to the sign-symmetric theorem is given, along with a conjecture for the one-dimensional, two-layer, nonreciprocal case.
MORE SPATIAL GAMES
Authors: NOWAK MARTIN A. , BONHOEFFER SEBASTIAN , MAY ROBERT M.
Published: November 2004

We extend our exploration of the dynamics of spatial evolutionary games [Nowak & May 1992, 1993] in three distinct but related ways. We analyse, first, deterministic versus stochastic rules; second, discrete versus continuous time (see Hubermann & Glance [1993]); and, third, different geometries of interaction in regular and random spatial arrays. We show that spatial effects can change some of the intuitive concepts in evolutionary game theory: (i) equilibria among strategies are no longer necessarily characterised by equal average payoffs; (ii) the strategy with the higher average payoff can steadily converge towards extinction; (iii) strategies can become extinct even though their basic reproductive rate (at very low frequencies) is larger than one. The equilibrium properties of spatial games are instead determined by “local relative payoffs.”

We characterise the conditions for coexistence between cooperators and defectors in the spatial prisoner’s dilemma game. We find that cooperation can be maintained if the transition rules give more weight to the most successful neighbours, or if there is a certain probability that cells may remain unoccupied in the next generations when they are surrounded by players with low payoffs. In this second case the cooperators can survive despite a very large payoff advantage to defectors. We also compute average extinction times for random drift in neutral spatial models. Finally we briefly describe the spatial dynamics of an interaction among three species which dominate each other in a cyclic fashion. The emphasis of this paper is presenting a variety of ideas and possibilities for further research in the evolutionary dynamics of spatial games. The overall conclusion is that interactions with local neighbours in 2- or 3-dimensional spatial arrays can promote coexistence of different strategies (such as cooperators and defectors in the Prisoner’s Dilemma), in situations where one strategy would exclude all others if the interactions occurred randomly and homogeneously.
THREE-DIMENSIONAL ROTATIONS AND DISCRETE-TIME DYNAMICAL SYSTEMS: DISCRETE SYMMETRIES IN CHAOS-ORDER TRANSITIONS
Authors: OKNIŃSKI A.
Published: November 2004

It is shown that rotations in three dimensions induce two-dimensional noninvertible discrete time dynamical systems from which well-known one-dimensional mappings follow, for example, the logistic equation. The noninvertible mappings can be interpreted in terms of the dynamics of a kicked spherical top and display new forms of dynamics. The most interesting behavior of the generalized dynamical systems considered is a transition from a nearly homogeneous chaos to various forms of discrete symmetries on a unit sphere.
A LEARNING ALGORITHM FOR OPTIMAL REPRESENTATION OF EXPERIMENTAL DATA
Authors: BREEDEN JOSEPH L. , PACKARD NORMAN H.
Published: November 2004

We have developed a procedure for finding optimal representations of experimental data. Criteria for optimality vary according to context; an optimal state space representation will be one that best suits one’s stated goal for reconstruction. We consider an ∞-dimensional set of possible reconstruction coordinate systems that include time delays, derivatives, and many other possible coordinates; and any optimality criterion is specified as a real valued functional on this space. We present a method for finding the optima using a learning algorithm based upon the genetic algorithm and evolutionary programming. The learning algorithm machinery for finding optimal representations is independent of the definition of optimality, and thus provides a general tool useful in a wide variety of contexts.
BASIN BIFURCATIONS OF TWO-DIMENSIONAL NONINVERTIBLE MAPS: FRACTALIZATION OF BASINS
Authors: MIRA C. , FOURNIER-PRUNARET D. , GARDINI L. , KAWAKAMI H. , CATHALA J.C.
Published: November 2004

Properties of the basins of noninvertible maps of a plane are studied using the method of critical curves. Different kinds of basin bifurcation, some of them leading to basin boundary fractalization are described. More particularly the paper considers the simplest class of maps that of a phase plane which is made up of two regions, one with two preimages, the other with no preimage.
COMMUNICATIONS USING CHAOTIC FREQUENCY MODULATION
Authors: BERNHARDT PAUL A.
Published: November 2004

Chaotic Frequency Modulation (CFM) provides the basis for a nonlinear communications system with (1) good noise suppression and (2) analogue signal encryption for private and secure communications links. CFM is a generalization of conventional Wideband Frequency Modulation (WFM) where the information about modulation samples mk are contained in the lengths of the periods pk for the kth cycle of the WFM waveform. A WFM modulator produces waveform periods described by an invertible function of the form pk=F(mk). Chaotic FM uses a map of the pulse periods to produce a noise-like pulse train even with a constant signal. The basis for CFM is a function pk=F(mk; pk−1, pk−2, …, pk−i), where i is the dimensionality of the map. A practical realization for a CFM transmitter employs an autonomous chaotic relaxation oscillator (ACRO) circuit for use as a chaotic voltage-controlled oscillator (CVCO). The ACRO is simple to construct, consisting of only two capacitors, one inductor, a bistable nonlinear element, and a modulated current source. The CVCO period (pk) is a nonlinear function of the current (mk) and the two previous pulse periods. Demodulation requires the use of at least three successive waveform-periods. Experimental and theoretical studies of the CVCO circuit have shown that (1) the ACRO return maps of pulse periods are embedded in three dimensions, (2) chaotic outputs are difficult to decode without prior knowledge of the circuit parameters, and (3) demodulation may be accomplished with a digital signal processor.
STABILIZING HIGHER PERIODIC ORBITS
Authors: PASKOTA M. , MEES A.I. , TEO K.L.
Published: November 2004

In this paper, we consider stabilization of chaotic dynamical systems onto higher periodic orbits. We give a necessary and sufficient condition for using local linear state feedback control for this purpose. The control is achieved using small, bounded perturbations, and the method proposed is shown to be effective even in the presence of relatively small random dynamical noise.
TRAJECTORY SCALING FUNCTION OF POLYNOMIAL CIRCLE MAPS
Authors: VALSAMMA K.M. , JOSEPH K. BABU
Published: November 2004

The universality of trajectory scaling function (TSF) for the polynomial form of the circle map in the quasiperiodic-to-chaos transition is discussed. It is found that the TSF gets bumpier with increase in the degree of inflection z, for both Golden and Silver Mean cases, and shows multiple scaling with increase in z, reflecting the monotone decrease of α with increasing z. The effect of noise is also studied.
HYPERCHAOTIC ATTRACTORS OF UNIDIRECTIONALLY-COUPLED CHUA’S CIRCUITS
Authors: KAPITANIAK TOMASZ , CHUA LEON O.
Published: November 2004

In this letter we discuss properties of hyperchaotic attractors of unidirectionally-coupled Chua’s circuits. Results from chaos synchronization theory allowed us to observe chaos-hyperchaos transition on 3D projections of the attractor.
EXPERIMENTAL SYNCHRONIZATION OF CHAOS USING CONTINUOUS CONTROL
Authors: KAPITANIAK TOMASZ , CHUA LEON O. , ZHONG GUO-QUN
Published: November 2004

We show experimentally that two identical chaotic Chua’s circuits can be synchronized by applying the method of continuous chaos control. The presented method is especially useful for higher-dimensional systems.
BIFURCATIONS AND TRANSITION TO CHAOS THROUGH THREE-DIMENSIONAL TORI
Authors: ANISHCHENKO V.S. , SAFONOVA M.A. , FEUDEL U. , KURTHS J.
Published: November 2004

The breakdown of three-dimensional tori T3 and the transition to chaos are studied numerically in a periodically forced system of two coupled logistic maps. We have shown that for small perturbations the breakdown of T3 possesses the same features as in the T2 case described by the theorem of Afraimovich and Shil’nikov. Remarkably, some indications for a chaotic motion on T3 are found.
FROM SINGLE WELL CHAOS TO CROSS WELL CHAOS: A DETAILED EXPLANATION IN TERMS OF MANIFOLD INTERSECTIONS
Authors: KATZ ANDREW L. , DOWELL EARL H.
Published: November 2004

The study of stable and unstable manifolds, and their intersections with each other, is a powerful technique for interpreting complex bifurcations of nonlinear systems. The escape phenomenon in the twin-well Duffing oscillator is one such bifurcation that is elucidated through the analysis of manifold intersections. In this paper, two escape scenarios in the twin-well Duffing oscillator are presented. In each scenario, the relevant manifold structures are examined for parameter values on either side of the escape bifurcation. Included is a description of the role of the hilltop saddle stable manifolds, which are known to separate the single well basins (should single well attractors exist). In each of the two bifurcation scenarios, it is shown through a detailed analysis of Poincaré maps that a homoclinic intersection of the manifolds of a specific period-3 saddle implies the destruction of the single well chaotic attractor. Although the Duffing oscillator is used to illustrate the ideas advanced here, it is thought that the approach will be useful for a variety of dynamical systems.
STEPS TOWARD UNMASKING SECURE COMMUNICATIONS
Authors: SHORT KEVIN M.
Published: November 2004

This work tests the level of security in secure communication systems based on nonlinear dynamics (NLD), or chaos. In these systems, a chaotic carrier signal is used in a type of spread-spectrum signaling system, with the added benefit that the hidden information signal is buried at something of the order of −30 dB with respect to the chaotic carrier. To investigate the level of security in such systems, an examination was conducted on a test set of chaotic carriers and hidden information signals prepared by the NLD research group at the Naval Research Lab. The hidden signals included a triangle wave, a period doubled signal, and a chaotic signal that was different from the chaotic carrier. The analysis process was to use NLD forecasting to predict the carrier dynamics, and then subtract away the predicted values to reveal the hidden signal or at least increase its signal-to-noise ratio with respect to the carrier. In each case, it was a simple task to determine the power spectrum of the hidden signal once the prediction of the carrier was removed. This was then used to create a “comb” filter to extract the correct frequencies from the FFT of the first two signals. When this was done, the hidden signals were recreated with almost perfect accuracy. In the third case, the hidden chaotic signal had a broadband component, so the spectrum was used to develop a Weiner filter which enabled the hidden signal to be reconstructed with only moderate accuracy, where the overall structure of the hidden chaotic signal was preserved, but the fine structure was lost. As a further test, the processing approach was applied to a voice signal hidden in one-dimensional Lorenz data at −35 dB. After subtracting away the carrier model, the voice signal was reconstructed with reasonable accuracy, and had the same characteristic structure. In this case, no secondary filtering was applied. The forecasting approach was then extended to allow for dynamic signal estimation using threshold detection, so that whenever a signal was detected, multiple predictions of the carrier behavior were made into the future. This was tested on a square wave embedded at −42 dB in Lorenz data. The extended approach was able to reveal the square wave with almost perfect precision, except in a few regions where it temporarily lost synchrony with the carrier. This allowed for the elimination of the secondary filtering requirement entirely. The final conclusion is that the secure communications systems based on chaotic carriers may be useful to increase privacy, but are not yet capable of providing a high level of security. The paper concludes with a discussion of measures which may be taken to improve the security of such systems so that they may be applicable to areas where higher security is required.
A UNIFIED FRAMEWORK FOR SYNCHRONIZATION AND CONTROL OF DYNAMICAL SYSTEMS
Authors: WU CHAI WAH , CHUA LEON O.
Published: November 2004

In this paper, we give a framework for synchronization of dynamical systems which unifies many results in synchronization and control of dynamical systems, in particular chaotic systems. We define concepts such as asymptotical synchronization, partial synchronization and synchronization error bounds. We show how asymptotical synchronization is related to asymptotical stability. The main tool we use to prove asymptotical stability and synchronization is Lyapunov stability theory. We illustrate how many previous results on synchronization and control of chaotic systems can be derived from this framework. We will also give a characterization of robustness of synchronization and show that master-slave asymptotical synchronization in Chua’s oscillator is robust.
INELASTIC INTERACTION OF BOUSSINESQ SOLITONS
Authors: CHRISTOV C.I. , VELARDE M.G.
Published: November 2004

Two improved versions of Boussinesq equation (Boussinesq paradigm) have been considered which are well-posed (correct in the sense of Hadamard) as an initial value problem: the Proper Boussinesq Equation (PBE) and the Regularized Long Wave Equation (RLWE). Fully implicit difference schemes have been developed strictly representing, on difference level, the conservation or balance laws for the mass, pseudoenergy or pseudomomentum of the wave system. Thresholds of possible nonlinear blow-up are identified for both PBE and RLWE.

The head-on collisions of solitary waves of the sech type (Boussinesq solitons) have been investigated. They are subsonic and negative (surface depressions) for PBE and supersonic and positive (surface elevations) for RLWE. The numerically recovered sign and sizes of the phase shifts are in very good quantitative agreement with analytical results for the two-soliton solution of PBE.

The subsonic surface elevations are found to be not permanent but to gradually transform into oscillatory pulses whose support increases and amplitude decreases with time although the total pseudoenergy is conserved within 10−10. The latter allows us to claim that the pulses are solitons despite their “aging” (which is felt on times several times the time-scale of collision).

For supersonic phase speeds, the collision of Boussinesq solitons has inelastic character exhibiting not only a significant phase shift but also a residual signal of sizable amplitude but negligible pseudoenergy. The evolution of the residual signal is investigated numerically for very long times.
PATTERN FORMATION IN ROTATING BÉNARD CONVECTION
Authors: NEUFELD M. , FRIEDRICH R.
Published: November 2004

Using a model equation we study pattern formation in rotating, high Prandtl-number Bénard convection in circular geometry and in a rectangular vessel with periodic boundary conditions. We report on drifting pattern, defect motion, Küppers-Lortz instability and domain wall turbulence. In circular geometry we observed spiral patterns which disappear and reappear in the Küppers-Lortz unstable regime. We define a pattern entropy for the patterns and show that this quantity is related to the Nusselt number.
SPIRAL FORMATION IN A BELOUSOV-ZHABOTINSKY MEDIUM BY PREMATURE RE-EXCITATION: VULNERABILITY
Authors: GÓMEZ-GESTEIRA M. , FERNÁNDEZ-GARCÍA G. , MUÑUZURI A.P. , PÉREZ-MUÑUZURI V. , KRINSKY V.I. , STARMER C.F. , PÉREZ-VILLAR V.
Published: November 2004

Spiral waves can be initiated in cardiac tissue by first stimulating it with a conditioning stimulus and then by a test stimulus at a different site. Because the resulting heart rhythm can be life threatening, this behaviour has been widely treated and the interval of time between conditioning and test stimuli has been labelled vulnerability. We hypothesize that the anisotropic cardiac structure was not essential for spiral initiation and reproduced it in a Belousov-Zhabotinsky (BZ) medium, which is continuous and characterized by isotropic diffusion coefficients. We observe that the different spatial extent of the medium (systems “quasi” 1D, 2D or 3D) influences the evolution of the test wave front. Even when the spatial extent of the third dimension exceeds a critical value, the region of vulnerability can disappear.