bluuebunny/crossref_metadata_2025 huggingface dataset:
Basis-set methods for the Dirac equation
Authors: Krauthauser C , Hill R N
Published: July 2002

The pathologies associated with finite basis-set approximations to the Dirac Hamiltonian HDirac are avoided by applying the variational principle to the bounded operator 1 / (H Dirac  W) where W is a real number that is not in the spectrum of HDirac. Methods of calculating upper and lower bounds to eigenvalues, and bounds to the wave-function error as measured by the L2 norm, are described. Convergence is proven. The rate of convergence is analyzed. Boundary conditions are discussed. Benchmark energies and expectation values for the Yukawa potential, and for the Coulomb plus Yukawa potential, are tabulated. The convergence behavior of the energy-weighted dipole sum rules, which have traditionally been used to assess the quality of basis sets, and the convergence behavior of the solutions to the inhomogeneous problem, are analyzed analytically and explored numerically. It is shown that a basis set that exhibits rapid convergence when used to evaluate energy-weighted dipole sum rules can nevertheless exhibit slow convergence when used to solve the inhomogeneous problem and calculate a polarizability. A numerically stable method for constructing projection operators, and projections of the Hamiltonian, onto positive and negative energy states is given.

PACS Nos.: 31.15Pf, 31.30Jv, 31.15-p
Nonlinear excitation and ionization of diatomic molecules by short laser pulses. Model of two active electrons in the field of a frozen core
Authors: Pegarkov A I
Published: July 2002

The dynamics of electron excitation and ionization of diatomic molecules in short laser pulses is studied within a model of two active 1D electrons moving in the field of a frozen core. It is shown for example for the N2 molecule that the model reproduces the spectrum of the pulse-free Σ electronic states very well. The N2 electron dynamics is examined numerically for short τ = 30 fs and ultra-short τ = 5 fs laser pulses with λ = 800 nm and intensity 1013 W/cm2 ÷ 1015 W/cm2 as well as for the resonant pulse with τ = 1 fs and λ = 147 nm, 1014 W/cm2 ÷ 1016 W/cm2. The phenomena of strong above-threshold absorption and resonant revival of electronic ground-state population in the ultra-short resonant pulse are found. Within the model, the quantum-mechanical picture of one-electron, two-electron, sequential, and nonsequential molecular ionizations is analyzed in detail in comparison with recent experimental results of Cornaggia and Hering, and Gibson et al. The model correctly explains the origin and nonlinear dynamics of the well-known "shoulder" in the N2+2 ion yield.

PACS Nos.: 33.80Rv, 33.80Wz
Compound multiplicity in the collisions of 4.1 A GeV/c 22Ne nuclei with nuclear emulsion
Authors: Abou-Moussa Z
Published: July 2002

This work displays a study of the compound multiplicity characteristics of 4.1 A GeV/c 22Neemulsion interactions, where the number of shower and grey particles taken together is termed as compound multiplicity, Nc. The present data are compared with the corresponding ones obtained for other projectiles at nearly the same momentum per nucleon. It is observed that while the average compound multiplicity depends on the mass number of the projectile, Ap, the value of the ratio /D(Nc) seems to be independent of Ap. The impact parameter is found to affect the shape of the compound multiplicity distribution. A positive linear dependence of the compound multiplicity on both the black and heavy charged particles is also noted. Finally, the results indicate that the value of  depends also on the target mass number.

PACS No.: 25.70
Seismic passive earth pressure coefficients using the method of characteristics
Authors: Kumar Jyant , Chitikela Sridhar
Published: July 2002

The method of characteristics was used to generate passive earth pressure coefficients for an inclined wall retaining cohesionless backfill material in the presence of pseudostatic horizontal earthquake body forces. The variation of the passive earth pressure coefficients Kpqand Kpγwith changes in horizontal earthquake acceleration coefficient due to the components of soil unit weight and surcharge pressure, respectively, has been obtained; a closed-form solution for Kpqis also provided. The passive earth resistance has been found to decrease sharply with an increase in the magnitude of horizontal earthquake acceleration. The computed passive earth pressure coefficients were found to be the lowest when compared to all of the previous solutions available in the literature.Key words: earth pressures, earthquakes, method of characteristics, retaining walls, sands.
GENERATING ALL THE MINIMAL SEPARATORS OF A GRAPH
Authors: BERRY ANNE , BORDAT JEAN-PAUL , COGIS OLIVIER
Published: July 2002

We present an efficient algorithm which computes the set of minimal separators of a graph in O(n3) time per separator, thus gaining a factor of n2 on the current best-time algorithms for this problem.

Our process is based on a new structural result, derived from the work of Kloks and Kratsch on listing all the minimal separators of a graph.
NUMBER THEORY, DYNAMICAL SYSTEMS AND STATISTICAL MECHANICS
Authors: KNAUF ANDREAS
Published: July 2002

In these lecture notes connections between the Riemann zeta function, motion in the modular domain and systems of statistical mechanics are presented.
FRAGMENTATION, COALESCENCE AND DEPOSITION OF SILICON CLUSTERS STUDIED BY MOLECULAR DYNAMICS
Authors: MAZZONE A. M.
Published: July 2002

Cluster deposition is a technique recently developed for the production of films of a nanometric thickness. The technique consists on driving a beam of clusters onto a substrate with an energy sufficient to obtain their fragmentation and the adhesion of the fragments to the substrate. Therefore the main mechanisms involved by this technique are (i) cluster fragmentation, (ii) cluster–substrate adhesion and (iii) coalescence of the deposited fragments.

The focus of this study is on these three mechanisms. To illustrate their peculiar features, three structures have been selected. Two of these structures, that is a cluster and a cluster dimer, are free standing. The third one represents a cluster deposited onto a substrate. The temperature response of the two free standing structures illustrates the effects of the cluster geometry and shape on the response to an external energy input. The comparison of these responses with the behavior occurring during deposition illustrates the main properties of cluster–substrate interactions.
MONTE CARLO STUDIES OF THE THREE-DIMENSIONAL ISING MODEL IN EQUILIBRIUM
Authors: HASENBUSCH MARTIN
Published: July 2002

We review Monte Carlo simulations of the Ising model and similar models in three dimensions that were performed in the last decade. Only recently, Monte Carlo simulations provide more accurate results for critical exponents than field theoretic methods, such as the ∊-expansion. These results were obtained with finite size scaling and "improved actions". In addition, we summarize Monte Carlo results for universal amplitude ratios, the interface tension, and the dimensional crossover from three to two dimensions.
FLUCTUATIONS AND MARKET FRICTION IN FINANCIAL TRADING
Authors: ROSENOW BERND
Published: July 2002

We study the relation between stock price changes and the difference in the volume of sell and buy orders. Using a soft spin model, we describe the price impact of order imbalances and find an analogy to the fluctuation–dissipation theorem in physical systems. We empirically investigate fluctuations and market friction for a major US stock and find support for our model calculations.
A COMPUTATIONAL METHOD FOR ENERGY LEVEL SPIN SPLITTING SIMULATION IN InAs/GaAs SEMICONDUCTOR QUANTUM DOTS
Authors: LI YIMING , VOSKOBOYNIKOV O. , LEE C. P. , SZE S. M. , TRETYAK O.
Published: July 2002

An impact of the spin–orbit interaction on the electron quantum confinement is considered theoretically for narrow gap semiconductor cylindrical quantum dots. To study the phenomena for InAs quantum dot embedded into GaAs semiconductor matrix, the effective one electronic band Hamiltonian, the energy position dependent electron effective mass approximation, and the spin-dependent Ben Daniel–Duke boundary conditions are considered, formulated and solved numerically. To solve the nonlinear Schrödinger equation, we propose a nonlinear iterative algorithm. This calculation algorithm not only converges for all simulation cases but also has a good convergent rate. With the developed quantum dot simulator, we study the effect of the spin–orbit interaction for narrow gap InAs/GaAs semiconductor cylindrical quantum dots. From the numerical calculations, it has been observed that the spin–orbit interaction leads to a sizeable spin-splitting of the electron energy states with nonzero angular momentum. Numerical evidence is presented to show the splitting result is strongly dependent on the quantum dot size.
RESONANT NORMAL FORMS AS CONSTRAINED LINEAR SYSTEMS
Authors: GAETA GIUSEPPE
Published: July 2002

We show that a nonlinear dynamical system in Poincaré–Dulac normal form (in ℝn) can be seen as a constrained linear system; the constraints are given by the resonance conditions satisfied by the spectrum of (the linear part of) the system and identify a naturally invariant manifold for the flow of the "parent" linear system. The parent system is finite dimensional if the spectrum satisfies only a finite number of resonance conditions, as implied e.g. by the Poincaré condition. In this case our result can be used to integrate resonant normal forms, and sheds light on the geometry behind the classical integration method of Horn, Lyapounov and Dulac.
THE d = 6, (2, 0)-TENSOR MULTIPLET COUPLED TO SELF-DUAL STRINGS
Authors: GUSTAVSSON ANDREAS
Published: July 2002

We show that the central charges that group theory allows in the (2, 0)-supersymmetry translations algebra arise from a string and a three-brane by commuting two supercharges. We show that the net force between two such parallel strings vanishes. We show that all the coupling constants are fixed numbers, due to supersymmetry, and self-duality of the three-form field strength. We obtain a charge quantization for the self-dual field strength, and show that when compactifying on a two-torus, it reduces to the usual quantization condition of N = 4 SYM with gauge group SU(2), and with coupling constant and theta angle given by the τ-parameter of the two-torus, provided that we pick that chiral theory which corresponds to a theta function with zero characteristics, as expected on manifolds of this form.
ENTROPY FROM THE FOAM II
Authors: GARATTINI REMO
Published: July 2002

A simple model of space–time foam, made by two different types of wormholes in a semiclassical approximation, is taken under examination: one type is a collection of Nw Schwarzschild wormholes, while the other one is made by Schwarzschild–Anti-de Sitter wormholes. The area quantization related to the entropy via the Bekenstein–Hawking formula hints a possible selection between the two configurations. Application to the charged black hole are discussed.
ANTIFERROMAGNETISM, STRIPES, AND SUPERCONDUCTIVITY IN THE t–J MODEL WITH COULOMB INTERACTION
Authors: HAN JUNGHOON , WANG QIANG-HUA , LEE DUNG-HAI
Published: July 2002

We study mean-field phases of the t–J model with long-range Coulomb interaction. In the order of increasing doping density we find a classical antiferromagnet, charge and spin stripes, and a uniform d-wave superconductor, at the realistic doping parameters. Both in-phase and anti-phase stripes exist as metastable configurations, but the in-phase stripes have a slightly lower energy. The dependence of the stripe width and the inter-stripe spacing on the doping is examined. Effects of fluctuations around the mean-field states are discussed.
SCALING OF THE NONLOCAL GROWTH EQUATIONS WITH SPATIALLY AND TEMPORALLY CORRELATED NOISE
Authors: TANG GANG , MA BENKUN
Published: July 2002

The Flory-type approach proposed by Hentschel and Family [Phys. Rev. Lett.66, 1982 (1991)] is generalized to analyze the scaling behavior of the nonlocal surface growth equations with long-range spatially and temporally correlated noise. The scaling exponents in both the weak- and strong-coupling regions are obtained. The growth equations studied include the nonlocal Kardar–Parisi–Zhang, nonlocal Sun–Guo–Grant, and nonlocal Lai–Das Sarma–Villain equation.
EXACT PROPERTIES OF THE CHEMICAL POTENTIAL-DENSITY RELATION AT FINITE TEMPERATURE IN THE HUBBARD MODEL
Authors: FENG SZE-SHIANG , MANCINI FERDINANDO
Published: July 2002

We draw some rigorous conclusions about the functional properties of the μ–ρ relation in the Hubbard model based on symmetry considerations and unitary transformations. It is shown that the charge susceptibility reaches its local extreme at half-filling. Exact expressions are obtained in two limiting cases.
COLOR SUPERCONDUCTIVITY
Authors: SCHÄFER THOMAS
Published: July 2002

We discuss recent results on color superconductivity in QCD at large chemical potential.
VORTEX IN CHIRAL SUPERCONDUCTING STATE
Authors: GORYO J.
Published: July 2002

We have investigated the vortex in chiral superconductors, especially in p-wave case. In chiral superconductors the Cooper pair has orbital angular momentum hence U(1), parity (P) and time reversal symmetry (T) are broken simultaneously. We have found that the vortex has fractional charge and fractional angular momentum which comes from P- and T-violation. The fractionalization of the angular momentum suggests that the vortex could be an anyon which obeys the fractional statistics. We have also pointed out that the electric field is induced near the vortex core and non-trivial electromagnetic phenomena are expected to occur.
CONCLUDING REMARKS ON CMR AND RELATED PROBLEMS: CONFERENCE SUMMARY II
Authors: TAKADA YASUTAMI , HOTTA TAKASHI
Published: July 2002

We review the talks on the colossal mangetoresistance (CMR) and its related subjects addressed at the Conference, together with a very brief explanation of our recent work. We also suggest some problems left in the future.
INTER - ISLAND TRANSPORT IN CdSe/ZnSe QUANTUM HETEROSTRUCTURES
Authors: WACHTER S. , DON DAL , BALDAUF M. , SCHMIDT M. , KURTZ E. , KLINGSHIRN C. , KALT H. , LITVINOV D. , GERTHSEN D.
Published: July 2002

We report on localization dynamics of excitons in ensembles of self–organized CdSe islands embedded in ZnSe. The experimental methods employed are temperature–dependent, spatially resolved photoluminescence (μ–PL), spatially integrated PL (macro-PL), as well as time–resolved PL (TRPL). We observe the well known non–monotonous shift of the PL maximum with temperature caused by redistribution of the excitons amongst the islands. The measured shift is compared with the exact shift of the bandgap deduced from μ–PL measurements and found to depend strongly on island size and distribution. These transport processes are recovered in the temporal evolution of the PL. The decaytime of the spectrally integrated PL reaches its maximum at exactly the same temperature at which the redhift of the macro–PL turns into a blueshift. In TRPL the PL–spectrum consists of two contributions. We put the emission on the high energy side down to excited states in the islands.
SUPERCOOLING AND INTERFACE MORPHOLOGY OF Bi4Ge3O12 FOR MELT CRYSTAL GROWTH: EXPERIMENTAL RESULTS
Authors: GOLYSHEV V. D. , GONIK M. A. , TSVETOVSKY V. B.
Published: July 2002

The results of in situ measurements of dependence of growth rate on supercooling of the Bi 4 Ge 3 O 12 (BGO) interface are presented. Supercooling was measured with an optical pyrometer through the growing crystal. The features of interfacial kinetics for (211) and (110) facets are described. The correlation between results of characterization and data on supercooling, and morphology of the interface is analyzed.
THEORETICAL STUDIES ON PIEZORESISTIVE EFFECT OF P-TYPE DIAMOND FILMS
Authors: WANG W. L. , LIAO K. J. , CAI C. Z. , KONG C. Y. , WANG S. X.
Published: July 2002

In this paper, based on the Fuchs and Sondheimer theory and valence band split-off model, a theoretical description of the piezoresistive effect in P-type heteroepitaxial diamond films was presented by solving the Boltzmann transport equation in the relaxation time approximation, in which a mixed scattering by lattice vibration, ionized impurities and surface was considered. A calculating expression of the piezoresistive effect has been developed in a parallel connection resistance model for the light-hole band, the heavy-hole band and the split-off band. The calculating results were in good agreement with the experimental data, indicating that the prezoresistive effect in diamond films was mainly ascribed to the hole band split-off under a uniaxial stress.
ELECTROCHEMICAL TECHNIQUES TO AID IN THE DEVELOPMENT OF IMPROVED CARBON OVERCOATS ON MAGNETIC STORAGE MEDIA
Authors: BLACKWOOD D. J. , GOH CHEE JOO , TOMCIK B.
Published: July 2002

With the trend of decreasing the thickness of the carbon overcoat on high-density magnetic recordings, the corrosion properties of a hard disk multilayer structure are becoming a hot issue. An ideal overcoat would be uniform across the disk's surface, have low porosity and electrical conductivity as well as being impermeable to water. However, in reality this is not viable and corrosion is inevitable. One possible method of improving the corrosion resistance of carbon overcoats is to introduce carbide bilayers. In this paper the corrosion protective properties of CrC/C and BC/C nanolaminated overcoat structures have been analyzed by an electrochemical technique based on LPR measurements. The results allowed an overcoat's resistance to be correlated to its porosity and a statistical method was developed to allow easy comparison of results. The results from the electrochemical measurements were correlated with a range of surface analysis techniques.
CORRELATION IDENTITIES AND APPLICATION
Authors: SUZUKI MASUO
Published: July 2002

General correlation identities are derived in a unified way using the quantum analysis,1–4 which include the well-known classical correlation identities5–7 such as the Ising correlation identities.5,6 In particular, quantum correlation identities are applied to the Heisenberg models and the transverse Ising model with local constants of motion. Integral identities are also presented in the spirit of the Gauss–Manin connection and they are applied to derive the generalized Bernoulli equation on the pressure and energy of ideal quantum gasses. There are many applications to condensed matter physics, which will be summarized in the present article together with an integrated list of papers on such applications in order to show how useful these correlation identities are.
Electronic Structure of Sr2RuO4
Authors: Noce C. , Cuoco M.
Published: July 2002

We introduce a microscopic model for the compound Sr 2 RuO 4, which is at the present the only known layered-perovskite superconductor without copper. The one-particle Hamiltonian is deduced by means of an approach that combines the extended Hückel theory and the tight-binding method. Adding two-body terms to this Hamiltonian, as the local Coulomb interaction and the Hund coupling, the magnetic properties are determined. It is found that the system is close to a ferromagnetic instability and this result supports a superconducting phase with p -wave symmetry.
Self-Field AC Losses on Ag-BSCCO(2223) Multifilamentary Tapes with Different Filament Arrangements
Authors: Polcari A. , Pace S. , Dhalle M. , Huang Y. , Witz G. , Marti F. , Flükiger R.
Published: July 2002

The influence of the geometrical parameters on the behaviour of the AC losses in multifilamentary Ag-BSCCO(2223) tapes is being more and more evident. Recently, the effects of configurational parameters like the ratio between the overall width and thickness of tapes without barriers as well as their precise arrangements has been put in evidence either theoretically or experimentally. With the goal to go deeper into the comprehension of this relation, we characterized a serie of multifilamentary tapes with gradually different filament arrangements. They were measured in a self-field AC transport system at different frequencies, for current values up to the critical state. The results so obtained are discussed taking into account of some theoretical models.
CHARACTERISTIC FEATURES OF THE EXOTIC SUPERCONDUCTORS: EVIDENCE FOR A COMMON PAIRING MECHANISM
Authors: BRANDOW BAIRD
Published: July 2002

We report on a comprehensive examination of the exotic superconductors (the materials so-labelled by Uemura and co-workers), to determine as far as possible the true systematics among their many anomalous features. In the crystal-chemistry aspects as well as in the electronic properties, we find features which appear to be universal for these materials, and also features which are clearly not universal but which are common enough to be considered typical for these materials. A number of implications are presented. There is strong evidence that all of these materials are sharing some "new" pairing mechanism, usually in addition to the conventional phonon mechanism.
TUNNELING CHARACTERISTICS OF INTRINSIC JOSEPHSON JUNCTIONS IN (Bi1-xPbx)2Sr2CaCu2Oy SINGLE CRYSTALS
Authors: OYA GIN-ICHIRO , NOZAWA SHINNOSUKE , IRIE AKINOBU
Published: July 2002

We have studied the current-voltage characteristics of intrinsic Josephson junctions in mesa-shaped Bi 2 Sr 2 CaCu 2 O y and ( Bi 1-x Pb x)2 Sr 2 CaCu 2 O y single crystals as a function of x. Pronounced Josephson tunneling characteristics, which are characterized by high critical current densities and multiple quasiparticle branches with clear subgap structures, have been observed for ( Bi ~0.8 Pb ~0.2)2 Sr 2 CaCu 2 O y. A strong correlation between the characteristics and structural modulation in this system has been found.
THE OSCILLATION–ROTATION ATTRACTORS IN THE FORCED PENDULUM AND THEIR PECULIAR PROPERTIES
Authors: SZEMPLIŃSKA-STUPNICKA WANDA , TYRKIEL ELŻBIETA
Published: July 2002

The paper is aimed at exploration of the properties of the oscillation–rotation attractors in the dissipative pendulum driven by external periodic force. The study of regions of existence of the orbits in the system control parameter plane, coexistence with other attractors, fractal structure of their basins of attraction, and the role they play in the onset of the tumbling chaos, give an insight into some peculiar features of the oscillation–rotation attractors and their bifurcational structures.
CHAOTIC PHASE SHIFT KEYING IN DELAYED CHAOTIC ANTICONTROL SYSTEMS
Authors: LU HONGTAO , TANG WALLACE K. S.
Published: July 2002

Based on the delayed feedback chaotic anticontrol systems, a new chaotic phase shift keying (CPSK) scheme is proposed for secure communications in this paper. The chaotic transmitter is a linear system with nonlinear delayed feedback in which a trigonometric function cos(·) is used. Such system can exhibit rich chaotic behavior with the choice of appropriate parameters. For an M-ary communication system where M=2n, each of these M possible symbols (n-bits) is firstly mapped to 2(m-1)π/M (with m=1, 2, …, M) which is used as the phase argument for the cos(·) function in the nonlinear feedback. Two different kinds of signals can be transmitted. In the first one, an appropriate linear combination of state variables is chosen as the transmitting signal based on the observer theory. In another one, a nonlinear component in the transmitter state equation is chosen. In both schemes, only a scalar chaotic signal is transmitted through the channel. Demodulation is based on the synchronization of the transmitter and the receiver, and different decoded phases correspond to different information signals.
A NOVEL NEURAL-WAVELET DIAGNOSTICS APPROACH: APPLICATION TO MAGNETIC FLOWMETER
Authors: GAO R. , ERYUREK E. , TSOUKALAS L. H.
Published: July 2002

Magnetic flow meters (magmeters) are instruments for measuring the velocity of flow in many industrial applications. The signal that comes from a magmeter is noisy and conventional approaches are often not effective enough in dealing with actual field noise. Furthermore, diagnostic functions are attracting increasing attention, due to the possibility of implementing them in an inexpensive and reliable manner in magmeter hardware. Neural networks have proven capabilities for both learning and data handling in noisy circumstances. In this paper, a novel approach based on wavelet neural networks is presented to attack these two objectives. The stability, accuracy and response time of the new approach has been tested, and found to be superior to conventional approaches.
A Dehn surgery description of regular finite cyclic covering spaces of rational homology spheres
Authors: Curtis Cynthia L.
Published: July 2002

We provide related Dehn surgery descriptions for rational homology spheres and a class of their regular finite cyclic covering spaces. As an application, we use the surgery descriptions to relate the Casson invariants of the covering spaces to that of the base space. Finally, we show that this places restrictions on the number of finite and cyclic Dehn fillings of the knot complements in the covering spaces beyond those imposed by Culler-Gordon-Luecke-Shalen and Boyer-Zhang.
A TRANSFER MATRIX APPROACH TO THE ENUMERATION OF COLORED LINKS
Authors: JACOBSEN J. L. , ZINN-JUSTIN P.
Published: July 2002

We propose a transfer matrix algorithm for the enumeration of alternating link diagrams with external legs, giving a weight n to each connected component. Considering more general tetravalent diagrams with self-intersections and tangencies allows us to treat topological (flype) equivalences. This is done by means of a finite renormalization scheme for an associated matrix model. We give results, expressed as polynomials in n, for the various generating functions up to order 19 (2-legged link diagrams), 15 (tangles) and 11 (6-legged links) crossings. The limit n→∞ is solved explicitly. We then analyze the large-order asymptotics of the generating functions. For 0≤n≤2 good agreement is found with a conjecture for the critical exponent, based on the KPZ relation.
UPPER BOUNDS ON LINKING NUMBERS OF THICK LINKS
Authors: DIAO Y. , ERNST C. , JANSE VAN RENSBURG E.J.
Published: July 2002

The maximum of the linking number between two lattice polygons of lengths n1, n2 (with n1 ≤ n2) is proven to be the order of n1 (n2)⅓. This result is generalized to smooth links of unit thickness. The result also implies that the writhe of a lattice knot K of length n is at most 26 n4/3/π. In the second half of the paper examples are given to show that linking numbers of order n1 (n2)⅓ can be obtained when [Formula: see text]. When [Formula: see text], it is further shown that the maximum of the linking number between these two polygons is bounded by [Formula: see text] for some constant c > 0. Finally the maximal total linking number of lattice links with more than 2 components is generalized to k components.
THE FERMIONIC ENTROPY IN DILATONIC BLACK HOLE BACKGROUND SPACETIME
Authors: SHEN YOU-GEN , CHEN DA-MING
Published: July 2002

The fermionic free energy and entropy are calculated in Garfinkle–Horowitz–Strominger dilatonic black hole background spacetime, by using 't Hfoot's brick wall model. It turns out that the fermionic entropy in Garfinkle–Horowitz–Strominger dilatonic black hole back ground spacetime is 7/2 times the Bosonic entropy.
WORMHOLES IN SPACETIMES WITH COSMOLOGICAL HORIZONS
Authors: BARCELÓ CARLOS
Published: July 2002

A generalization of the asymptotic wormhole boundary condition for the case of spacetimes with a cosmological horizon is proposed. In particular, we consider de Sitter spacetime with small cosmological constant. The wave functions selected by this proposal are exponentially damped in WKB approximation when the scale factor is large but still much smaller than the horizon size. In addition, they only include outgoing gravitational modes in the region beyond the horizon. We argue that these wave functions represent quantum wormholes and compute the local effective interactions induced by them in low-energy field theory. These effective interactions differ from those for flat spacetime in terms that explicitly depend on the cosmological constant.
REFLECTION/TRANSMISSION COEFFICIENTS AT A PLANE INTERFACE IN DISSIPATIVE AND NONDISSIPATIVE ISOTROPIC MEDIA: A COMPARISON
Authors: BROKEŠOVÁ JOHANA
Published: July 2002

The problem of reflection/transmission of plane waves in homogeneous isotropic dissipative media is investigated. In dissipative media, the elastic moduli, seismic velocities and slowness vectors are complex-valued and frequency-dependent. Results of extensive computations of R/T coefficients for plane waves incident at a plane interface are presented and discussed. In all cases, the "reference R/T coefficients" are considered, computed for a fixed frequency equal to the reference frequency fr, for which the elastic moduli are specified. The influence of angle of incidence i and attenuation angle γ of the incident wave on the coefficients is studied in detail. In general, the differences between the moduli of the R/T coefficients for dissipative and nondissipative models are usually small for realistic Q's and γ's. These differences are more distinct in critical and post-critical regions for the reflection coefficients, particularly for small Q's, large contrast of Q's across the interface, and for large |γ|'s (say, |γ|>50°). The differences between the phases of R/T coefficients for dissipative and nondissipative media may be larger. For some γ's, the signs of the phases for dissipative and nondissipative media may be roughly opposite, even for very high Q's.
STEPPED SURFACES: A CHALLENGE FOR QUANTITATIVE LEED ANALYSIS
Authors: JONA F.
Published: July 2002

Determination of the atomic structure of stepped surfaces by quantitative low-energy electron diffraction (LEED) analysis is very difficult when the spacings between layers parallel to the surface become significantly smaller than about 0.9 Å. For most of the computer programs widely used in LEED crystallography the problem is caused by numerical instabilities and lack of convergence. However, the CHANGE computer program has had remarkable success on surfaces with interlayer spacings as small as 0.5 Å. Advantages and disadvantages of this program are briefly discussed. CHANGE is now available to run conveniently on desk-top personal computers.
The Bilhaut-Cloquet Procedure Revisited
Authors: Tonkin Ma , Rumball Km
Published: July 2002

We have found the Bilhaut-Cloquet procedure, with certain modifications, to be a useful method of reconstruction of thumb duplication. Seven thumbs were reviewed at an average follow-up of two years. A thumb of normal size and stability was obtained. Interphalangeal joint motion was 50% of normal. Nail ridging was considered to be less than satisfactory in one case only.
MEASURING SHOCK IN FINANCIAL MARKETS
Authors: ZUMBACH GILLES O. , DACOROGNA MICHEL M. , OLSEN JØRGEN L. , OLSEN RICHARD B.
Published: July 2002

Analogous to the Richter scale for earthquakes, we introduce the Scale of Market Shocks (SMS), an "event" scale to quantify the size of shocks in financial markets. It is based on price volatilities and computed by integrating volatilities over time horizons ranging from 1 hour to 42 days. The SMS is computed using quality high frequency market data and can be constructed for any market.

We compute the SMS for the foreign exchange market. For two major FX rates, we study the relation between SMS peaks and major "world events". We measure also the correlation between the Scale of Market Shocks index and the size of the subsequent price movements and show a high correlation for short time intervals.
DRIVING FORCE IN INVESTMENT
Authors: CAPOCCI ANDREA , ZHANG YI-CHENG
Published: July 2002

We study investment strategy in different models of financial markets, where the investors cannot attain a perfect knowledge about available assets. The investor spends a certain effort to get information; this allows him to better choose the investment strategy, and puts a selective pressure upon assets. The best strategy is then a compromise between diversification and effort to get information.
EXISTENCE OF GENERALISED PARETO EQUILIBRIA FOR CONSTRAINED MULTIOBJECTIVE GAMES
Authors: CUBIOTTI PAOLO
Published: July 2002

A model of multiobjective game is considered where the actual strategy space of each player depends on the other players' behaviour. A notion of generalised Pareto equilibrium is defined, which extends the usual notion of Pareto equilibrium considered in the literature. Existence results for such equilibria are established. In particular, some known results are extended and improved.
SPATIAL PATTERNS INDUCED BY RANDOM SWITCHING
Authors: BUCETA J. , LINDENBERG KATJA , PARRONDO J. M. R.
Published: July 2002

We propose a mechanism whereby a random alternation of two dynamics each leading to a different homogeneous state can lead to complex ordered structures. The proposed general formalism, based on the ideas of so-called paradoxical games, is illustrated via numerical simulations of particular examples. The relevance of the present study to other situations that lead to pattern formation, such as reaction-diffusion systems, is noted.
MODELING A SIMPLE CHOICE TASK: STOCHASTIC DYNAMICS OF MUTUALLY INHIBITORY NEURAL GROUPS
Authors: BROWN ERIC , HOLMES PHILIP
Published: July 2002

We describe the dynamical and bifurcational behavior of two mutually inhibitory, leaky, neural units subject to external stimulus, random noise, and "priming biases". The model describes a simple forced choice experiment and accounts for varying levels of expectation and control. By projecting the model's dynamics onto slow manifolds, using judicious linear approximations, and solving for one-dimensional (reduced) probability densities, analytical estimates are developed for reaction time distributions and shown to compare satisfactorily with "full" numerical data. A sensitivity analysis is performed and the effects of parameters assessed. The predictions are also compared with behavioral data. These results may help correlate low-dimensional models of stochastic neural networks with cognitive test data, and hence assist in parameter choices and model building.
PROBABILISTIC DYNAMICS OF TWO-LAYER GEOPHYSICAL FLOWS
Authors: CHUESHOV IGOR , DUAN JINQIAO , SCHMALFUSS BJÖRN
Published: July 2002

The two-layer quasigeostrophic flow model is an intermediate system between the single-layer two-dimensional barotropic flow model and the continuously stratified three-dimensional baroclinic flow model. This model is widely used to investigate basic mechanisms in geophysical flows, such as baroclinic effects, the Gulf stream and subtropical gyres.

We consider the two-layer quasigeostrophic flow model under stochastic wind forcing on the top layer. The fluctuating part of the wind forcing is modeled as the generalized time derivative of a Wiener process. We first transform this stochastic two-layer fluid system into a coupled system of random partial differential equations. Then we prove that the stochastic two-layer fluid system has finite sets of asymptotically determining functionals (such as determining modes and determining nodes) in probability. Furthermore, we show that the asymptotic probabilistic dynamics of this system depends only on the top fluid layer. Namely, in the probability sense and asymptotically, the dynamics of the two-layer quasigeostrophic fluid system is determined by the top layer. In other words, the bottom layer is slaved by the top layer. This conclusion is true provided that the Wiener process and the fluid parameters satisfy a certain condition. In particular, this latter condition is satisfied when the trace of the covariance operator of the Wiener process is small enough and the Ekman constant r is sufficiently large.
SPATIO-TEMPORAL CHAOS IN AN ECOLOGICAL COMMUNITY AS A RESPONSE TO UNFAVOURABLE ENVIRONMENTAL CHANGES
Authors: PETROVSKII SERGEI V. , MALCHOW HORST
Published: July 2002

The impact of ecological chaos on population dynamics has been an issue of intense discussion over the last decade. While many authors consider chaotic dynamics as a favourable factor facilitating species biodiversity, there is also a strong opinion that chaos may enhance population extinction. In this paper we show that chaotic spatio-temporal dynamics in an ecological community can arise as a response of the community to unfavourable environmental changes. Appearing in that way, chaos can prevent species extinction in a situation when it would be inevitable otherwise. We also show that an essential consequence of chaotic dynamics is that the issue of species extinction is subject to the size of the domain inhabited by the population, the extinction more likely happens in a small domain than in a large one.
INFORMATION BOTTLENECKS, CAUSAL STATES, AND STATISTICAL RELEVANCE BASES: HOW TO REPRESENT RELEVANT INFORMATION IN MEMORYLESS TRANSDUCTION
Authors: SHALIZI COSMA ROHILLA , CRUTCHFIELD JAMES P.
Published: July 2002

Discovering relevant, but possibly hidden, variables is a key step in constructing useful and predictive theories about the natural world. This brief note explains the connections between three approaches to this problem: the recently introduced information-bottleneck method, the computational mechanics approach to inferring optimal models, and Salmon's statistical relevance basis.
INFERENCE VERSUS IMPRINT IN CLIMATE MODELING
Authors: PALMER A. J. , SCHNEIDER T. L. , BENJAMIN L. A.
Published: July 2002

A statistical inference method known as ε-machine reconstruction is introduced as a modeling procedure for turbulent transport processes in a climate model. Observational data on the atmospheric boundary layer obtained with a radar wind profiler, a radio-acoustic sounding system, and a Raman lidar system was assembled to construct this type of model for use within the unresolved (sub-grid) scales of a numerical climate model. An ensemble of 500 single-column model runs using the inferred sub-grid turbulent transport models demonstrated comparable performance to an identical ensemble of runs using the standard, eddy-diffusivity parametrizations for the turbulent transport. The primary advantages of the ε-machine models are that they are a less biased modeling framework for complex processes such as turbulent transport, and that they are more memory efficient.
Highly continuous Runge-Kutta interpolants
Authors: Higham D. J.
Published: July 2002

To augment the discrete Runge-Kutta solutlon to the mitlal value
problem, piecewlse Hermite interpolants have been used to provide a
continuous approximation with a continuous first derivative We show
that it M possible to construct mterpolants with arbltrardy many
continuous derivatives which have the same asymptotic accuracy and
basic cost as the Hermite interpol ants. We also show that the
usual truncation coefficient analysis can be applied to these new
interpolants, allowing their accuracy to be examined in more detad
As an Illustration, we present some globally C2 interpolants for
use with a popular 4th and 5th order Runge-Kutta pair of Dormand
and Prince, and we compare them theoretically and numerically with
existing interpolants.
Concurrency control for high contention environments
Authors: Franaszek Peter A. , Robinson John T. , Thomasian Alexander
Published: July 2002

Future transaction processing systems may have substantially higher levels of concurrency due to reasons which include: (1) increasing disparity between processor speeds and data access latencies, (2) large numbers of processors, and (3) distributed databases. Another influence is the trend towards longer or more complex transactions. A possible consequence is substantially more data contention, which could limit total achievable throughput. In particular, it is known that the usual locking method of concurrency control is not well suited to environments where data contention is a significant factor.

Here we consider a number of concurrency control concepts and transaction scheduling techniques that are applicable to high contention environments, and that do not rely on database semantics to reduce contention. These include
access invariance
and its application to prefetching of data, approximations to
essential blocking
such as
wait depth limited
scheduling, and
phase dependent
control. The performance of various concurrency control methods based on these concepts are studied using detailed simulation models. The results indicate that the new techniques can offer substantial benefits for systems with high levels of data contention.
Getting raster ellipses right
Authors: McIlroy M. Douglas
Published: July 2002

A concise, incremental algorithm for raster approximations to ellipses in standard position produces approximations that are good to the last pixel even near octant boundaries or the thin ends of highly eccentric ellipses. The resulting approximations commute with reflection about the diagonal and are mathematically specifiable without reference to details of the algorithm.
Engineering a simple, efficient code-generator generator
Authors: Fraser Christopher W. , Hanson David R. , Proebsting Todd A.
Published: July 2002

Many code-generator generators use tree pattern matching and dynamic programming. This paper describes a simple program that generates matchers that are fast, compact, and easy to understand. It is simpler than common alternatives: 200–700 lines of Icon or 950 lines of C versus 3000 lines of C for Twig and 5000 for burg. Its matchers run up to 25 times faster than Twig's. They are necessarily slower than burg's BURS (bottom-up rewrite system) matchers, but they are more flexible and still practical.
New approximation algorithms for graph coloring
Authors: Blum Avrim
Published: July 2002

The problem of coloring a graph with the minimum number of colors is well known to be NP-hard, even restricted to
k
-colorable graphs for constant
k
≥ 3. This paper explores the approximation problem of coloring
k
-colorable graphs with as few additional colors as possible in polynomial time, with special focus on the case of
k
= 3.

The previous best upper bound on the number of colors needed for coloring 3-colorable
n
-vertex graphs in polynomial time was
O(√n / √log n
colors by Berger and Rompel, improving a bound of
O(√n)
colors by Wigderson. This paper presents an algorithm to color any 3-colorable graph with
O(n
3/8
polylog(
n
)) colors, thus breaking an “

O((n
1/2-o(1)
)

barrier”. The algorithm given here is based on examining second-order neighborhoods of vertices, rather than just immediate neighborhoods of vertices as in previous approaches. We extend our results to improve the worst-case bounds for coloring
k
-colorable graphs for constant
k
> 3 as well.
Algorithm 734: A Fortran 90 code for unconstrained nonlinear minimization
Authors: Buckley A. G.
Published: July 2002

This paper describes a Fortran 90 implementation of ACM Transactions on Mathematical Software Algorithm 630, a minimization algorithm designed for use in a limited-memory environment. It includes implementation of the Buckley-LeNir method, Nocedal's limited memory algorithm, and an experimental limited-memory implementation of a factored update due to Powell, as well as a fairly standard quasi-Newton implementation due originally to Shanno. This algorithm uses a number of the new features of Fortran 90 to offer capabilities that were not formerly available.
A √N algorithm for mutual exclusion in decentralized systems
Authors: Maekawa Mamoru
Published: July 2002

An algorithm is presented that uses only
c√N
messages to create mutual exclusion in a computer
network, where
N
is the number of nodes and
c
a constant between 3 and 5. The algorithm is
symmetric and allows fully parallel operation.
A structured approach for the definition of the semantics of active databases
Authors: Fraternali Piero , Tanca Letizia
Published: July 2002

Active DBMSs couple database technology with rule-based programming to achieve the capability of reaction to database (and possibly external) stimuli, called
events
. The reactive capabilities of active databases are useful for a wide spectrum of applications, including security, view materialization, integrity checking and enforcement, or heterogeneous database integration, which makes this technology very promising for the near future. An active database system consists of a (passive) database and a set of
active rules
; the most popular form of active rule is the so-called
event-condition-action
(ECA) rule, which specifies an action to be executed upon the occurrence of one or more events, provided that a condition holds. Several active database systems and prototypes have been designed and partially or completely implemented. Unfortunately, they have been designed in a totally independent way, without the support of a common theory dictating the semantics of ECA rules, and thus often show different behaviors for rules with a similar form. In this article we consider a number of different possible options in the behavior of an active DBMS, based on a broad analysis of some of the best known implemented systems and prototypes. We encode these options in a user-readable form, called
Extended ECA
. A rule from any existing system can be rewritten in this formalism making all the semantic choices apparent. Then an EECA rule can be automatically translated into an internal (less readable) format, based on a logical style, which is called
core
format: the execution semantics of core rules is specified as the fixpoint of a simple transformation involving core rules. As an important premise to this research, a semantics for database updates and transactions has also been established, with respect to a notion of state that comprises both data and events. The article also presents an extensive bibliography on the subject of active databases.
A knowledge-based approach for the validation of simulation models
Authors: Birta Louis G. , Özmizrak F. Nur
Published: July 2002

A new perspective of the validation problemfor simulation models is formulated in this article. The approach is knowledge-based and focuses on behavioral validation. It has the important feature of providing a basis for the development of a software environment that can automate the validation activity. Discrete, continuous and combined simulation models can be treated in a uniform manner.

The key element of the approach is a validation knowledge base (VKB). This is developed as three disjoint sets of relationships among the input and output variables of the simulation model. These relationships serve to capture all aspects of expected behavior of the simulation model. A simple characterization of model behavior is presented which provides the basis for specifying the relationships from which the VKB is constructed

The utilization of all the information in the VKB in an efficient way is an important subgoal of our system architecture. This requirement gives rise to an experiment design problem. This problem is carefully formulated and examined within the framework of the behavior characterizations that exist in the VKB. In particular, a basis for its solution is established in a constraint set framework by carrying out a transformation on the relationships within the VKB. The constraint set context for the problem has the advantage of providing an environment which not only facilitates analysis but also enables the application of a variety of solution techniques.
On the notion of inheritance
Authors: Taivalsaari Antero
Published: July 2002

One of the most intriguing—and at the same time most problematic—notions in object-oriented programing is
inheritance
. Inheritance is commonly regarded as the feature that distinguishes object-oriented programming from other modern programming paradigms, but researchers rarely agree on its meaning and usage. Yet inheritance of often hailed as a solution to many problems hampering software development, and many of the alleged benefits of object-oriented programming, such as improved conceptual modeling and reusability, are largely credited to it. This article aims at a comprehensive understanding of inheritance, examining its usage, surveying its varieties, and presenting a simple taxonomy of mechanisms that can be seen as underlying different inheritance models.