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  • 1
    ISSN: 1572-8358
    Schlagwort(e): biological rhythms ; oscillatory enzymes ; chaos ; dissipative structures ; cell behaviour
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The numerical study of a glycolytic model formed by a system of three delay differential equations reveals a multiplicity of stable coexisting states: birhythmicity, trirhythmicity, hard excitation and quasiperiodic with chaotic regimes. For different initial functions in the phase space one may observe the coexistence of two different quasiperiodic motions, the existence of a stable steady state with a stable torus, and the existence of a strange attractor with different stable regimes (chaos with torus, chaos with bursting motion, and chaos with different periodic regimes). For a single range of the control parameter values our system may exhibit different bifurcation diagrams: in one case a Feigenbaum route to chaos coexists with a finite number of successive periodic bifurcations, in other conditions it is possible to observe the coexistence of two quasiperiodicity routes to chaos. These studies were obtained both at constant input flux and under forcing conditions.
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Celestial mechanics and dynamical astronomy 78 (2000), S. 167-195 
    ISSN: 1572-9478
    Schlagwort(e): chaos ; numerical tools ; Nekhoroshev ; Chirikov
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract It is already known (Froeschlé, Lega and Gonczi, 1997) that the Fast Lyapunov Indicator (FLI), that is the computation on a relatively short time of the largest Lyapunov indicator, allows to discriminate between ordered and weak chaotic motion. We have found that, under certain conditions, the FLI also discriminates between resonant and non-resonant orbits, not only for two-dimensional symplectic mappings but also for higher dimensional ones. Using this indicator, we present an example of the Arnold web detection for four and six-dimensional symplectic maps. We show that this method allows to detect the global transition of the system from an exponentially stable Nekhoroshev’s like regime to the diffusive Chirikov’s one.
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Celestial mechanics and dynamical astronomy 78 (2000), S. 197-210 
    ISSN: 1572-9478
    Schlagwort(e): chaos ; KAM tori ; cantori ; asymptotic curves
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We find the form of cantori surrounding an island of stable motion in the standard map for various values of the nonlinearity parameter K near the value K = 5 (much larger than the critical value K cr = 0.971635...). The asymptotic curves of unstable periodic orbits inside the cantorus cross it after a certain time and then escape to the large chaotic sea. For K = 5 the crossing time (in appropriate units) is t = 1 and the escape time is t = 2. For K = 4.998 the crossing time is t = 7 and the escape time t = 23000. This delay of escape is due to the existence of higher order cantori, with very small gaps. We found that, as K increases the noble torus [2,4,1,1,..] is destroyed before the destruction of the higher order tori [2,4,1,1,1,1,2,1,...] and [2,4,1,1,1,1,3,1,...]. Thus the torus with the simplest noble number is not the last KAM curve to be destroyed. Then we find that nearby orbits deviate considerably, but the average times spent near various resonance before escape are very similar.
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Celestial mechanics and dynamical astronomy 74 (1999), S. 59-67 
    ISSN: 1572-9478
    Schlagwort(e): planetary systems ; Liapunov exponents ; chaos ; symplectic integration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Equations are presented for the computation of tangent maps for use in nearly Keplerian motion, approximated by use of a symplectic leapfrog map. The resulting algorithms constitute more accurate and efficient methods to obtain the Liapunov exponents and the state transition matrix, and can be used to study chaos in planetary motions, as well as in orbit determination procedures from observations. Applications include planetary systems, satellite motions and hierarchical, nearly Keplerian systems in general.
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Celestial mechanics and dynamical astronomy 74 (1999), S. 111-146 
    ISSN: 1572-9478
    Schlagwort(e): Mimas–Tethys system ; chaos ; secondary resonances ; tides ; capture probability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We have investigated the role of the 200 yr period discovered by Vienne and Duriez (1992) on the tidal evolution of the Mimas–Tethys system through the 2:4 ii′ present resonance. Three terms are found to generate this period. We present a perturbed‐pendulum model in which these terms bring about a perturbation to the ideal ii′ resonance pendulum, which is in a direct ratio to the eccentricity e′ of Tethys. Although e′ is now very small, it is shown that this quantity could have been much greater in the past. We also show, thanks to this model, that these terms may have brought about a stochastic layer of noticeable width at the time of capture in the ii′ resonance, with the consequence that the possible values of the inclination i of Mimas before capture range from 0.4° to 0.6° (these uncertainties arise from the present uncertainties on e′). The role of each one of the three terms is examined in the appearance of chaos. A capture into the 1/1 secondary resonance (between the libration period of the primary ii′ resonance and the period of about 200 yr) is found possible. It means that the system could have experienced several captures in the primary resonance, instead of a single one, and that i could have been, with this assumption, much lower than 0.4°. A probability of capture into this secondary resonance as a function of the eccentricity of Tethys on encounter is derived, using Malhotra's method (Malhotra, 1990). Allan's values of i = 0.42° and e′ ≈ 0 (Allan, 1969) are therefore called into question, and taking e′ ≠ 0 is shown to be absolutely necessary if we want to understand the phenomena at work in the Mimas–Tethys system.
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Celestial mechanics and dynamical astronomy 76 (2000), S. 23-34 
    ISSN: 1572-9478
    Schlagwort(e): one dimensional three-body problem ; triple collision ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We consider the motions of particles in the one-dimensional Newtonian three-body problem as a function of initial values. Using a mapping of orbits to symbol sequences we locate the initial values leading to triple collisions. These turn out to form curves which give clear structure to the region in which the motions depend sensitively on initial conditions. In addition to finding the triple collision orbits we also locate orbits which end up to a triple collision in both directions of time, that is, orbits which are finite both in space and time.
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Celestial mechanics and dynamical astronomy 76 (2000), S. 187-214 
    ISSN: 1572-9478
    Schlagwort(e): three-body problem ; triple collision ; binary collision ; escape ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Dominant factors for escape after the first triple-encounter are searched for in the three-body problem with zero initial velocities and equal masses. By a global numerical survey on the whole initial-value space, it is found that not only a triple-collision orbit but also a particular family of binary-collision orbits exist in the set of escape orbits. This observation is justified from various viewpoints. Binary-collision orbits experiencing close triple-encounter turn out to be close to isosceles orbits after the encounter and hence lead to escape. Except for a few cases, binary-collision orbits of near-isosceles slingshot also escape.
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Celestial mechanics and dynamical astronomy 78 (2000), S. 17-46 
    ISSN: 1572-9478
    Schlagwort(e): asteroids ; proper elements ; chaos ; families
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract For the orbits with low to moderate inclination and eccentricity, in the asteroid main belt, the analytically computed proper elements are accurate to a level very close to the best result achievable by any analytical theory. This fundamental limitation results from the infinite web of resonances and because of the occurrence of chaotic motions. Still, there are some regions of the belt in which these proper elements are of degraded accuracy, thus preventing a reliable definition of asteroid families and detailed studies of the dynamical structure. We have used a different method to compute asteroid proper elements, following the approach introduced in the LONGSTOP project to describe the secular dynamics of the major outer planets. By applying purely numerical techniques, we produced so-called ‘synthetic’ proper elements for a catalog of 10,256 asteroids with osculating semimajor axes between 2.5 and 4.0 AU. The procedure consisted of simultaneous integration of asteroid and planetary orbits for 2 Myr, with online filtering of the short-periodic perturbations. The output of the integration was spectrally resolved, and the principal harmonics (proper values) extracted from the time series. For each asteroid we have also tested the accuracy and stability in time of the proper elements, and estimated the maximum Lyapunov Characteristic Exponent to monitor the chaotic behaviors. This provided information on the reliability of the data for each orbit, in particular allowing to select 1,852 cases for an extended integration (10 Myr) of the orbits showing instability. The results indicate that for more than half of the cases the proper elements have a time stability improved by more than a factor 3 with respect to the elements computed by the previous analytical theory. But of course there are also unstable cases for which the proper elements are less accurate and reliable, the extreme examples being 23 orbits exhibiting hyperbolic escape from the solar system. This form of escape from the asteroid belt could be responsible for a significant mass loss over the age of the solar system.
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Celestial mechanics and dynamical astronomy 64 (1996), S. 93-105 
    ISSN: 1572-9478
    Schlagwort(e): asteroids ; resonance ; chaos ; Kirkwood gaps
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The utilization of chaotic dynamics approaches allowed the identification of many modes of motion in resonant asteroidal dynamics. As these dynamical systems are not integrable, the motion modes are not separated and one orbit may transit from one mode to another. In some cases, as in the \31 resonance, these transitions may lead, in a relatively short time scale, to eccentricities so high that the asteroid may approach the Sun and be destroyed. In the \21 and \32 resonances these transitions are much slower and only indirect estimations of the time which is needed for a generic asteroid to leave the resonance are possible. It may reach hundreds of million years in the more robust regions of the \21 resonance and a time of the order of billions of years in those of the \32 resonance. These values are consistent with the observed depletion of the \21 resonance (only a few asteroids known while almost 60 asteroids are known in the \32 resonance).
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Celestial mechanics and dynamical astronomy 61 (1995), S. 287-313 
    ISSN: 1572-9478
    Schlagwort(e): Two-body problem ; radiation pressure ; horseshoes ; chaos ; three-body problem
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study a perturbed Newtonian two-body problem, in which the perturbation is due to a force field of constant magnitude but rotating direction. By considering this system as a perturbation of the non-rotating case a Melnikov-type analysis allows us to show the existence of horseshoes in the level sets of the Hamiltonian and the subsequent sensitive dependence on initial conditions and non-integrability. We discuss the consequences of these results for a particular planar restricted three-body problem.
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Celestial mechanics and dynamical astronomy 70 (1998), S. 181-200 
    ISSN: 1572-9478
    Schlagwort(e): chaos ; dynamics ; comets ; NEAs ; Lyapunov exponent
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The dynamics of two families of minor inner solar system bodies that suffer frequent close encounters with the planets is analyzed. These families are: Jupiter family comets (JF comets) and Near Earth Asteroids (NEAs). The motion of these objects has been considered to be chaotic in a short time scale,and the close encounters are supposed to be the cause of the fast chaos. For a better understanding of the chaotic behavior we have computed Lyapunov Characteristic Exponents (LCEs) for all the observed members of both populations. LCEs are a quantitative measure of the exponential divergence of initially close orbits. We have observed that most members of the two families show a concentration of Lyapunov times (inverse of LCE) around 50–100yr. The concentration is more pronounced for JF comets than for NEAs, among which a lesser spread is observed for those that actually cross the Earth's orbit (mean perihelion distance q 〈 1.05 AU). It is also observed that a general correspondence exists between Lyapunov times and the time between consecutive encounters. A simple model is introduced to describe the basic characteristics of the dynamical evolution. This model considers an impulsive approach, where the particles evolve unperturbedly between encounters and suffer ‘kicks’ in semimajor axis at the encounters. It also reproduces successfully the short Lyapunov times observed in the numerical integrations and is able to estimate the dynamical lifetimes of comets during a stay in the Jupiter family in correspondence with previous estimates. It has been demonstrated with the model that the encounters with the largest effect on the exponential growth of the distance between initially nearby orbits are neither the infrequent deep encounters, nor the frequent and far ones; instead, the intermediate approaches have the most relevant contribution to the error growth. Such encounters are at a distance a few times the radius of the Hill's sphere of the planet (e.g. 3). An even simpler model allows us to get analytical estimates of the Lyapunov times in good agreement with the values coming from the model above and the numerical integrations. The predictability of the medium‐term evolution and the hazard posed to the Earth by those objects are analysed in the Discussion section.
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Optical review 5 (1998), S. 280-284 
    ISSN: 1349-9432
    Schlagwort(e): semiconductor laser ; optical feedback ; chaos ; relaxation oscillation ; linear stability analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The stability enhancement of laser output power for the change of external cavity position in semiconductor lasers with optical feedback is observed by experiment. The relaxation oscillation frequency which plays an important role in the dynamics of the nonlinear system is also investigated as a function of the external cavity length. The period of the stability enhancement along the position of the external cavity is exactly coincident with the length corresponding to the relaxation oscillation frequency of the solitary laser. The experimental results are compared with theoretical and excellent coincidence between the two is found.
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Optical review 6 (1999), S. 359-364 
    ISSN: 1349-9432
    Schlagwort(e): semiconductor laser ; photorefractive optical feedback ; instability ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The dynamics of semiconductor lasers with photorefractive phase conjugate optical feedback are experimentally studied. Photorefractive fringes considered here are rather static compared with time fluctuations of laser output power. Therefore, it is expected that a semiconductor laser with photorefractive feedback shows similar dynamics to those with conventional optical feedback. We examine relaxation oscillation and external cavity modes of laser output power in the presence of photorefractive phase conjugate feedback. It is proved that the dynamics of photorefractive phase conjugate feedback are fundamentally the same as those of conventional optical feedback.
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Optical review 6 (1999), S. 399-401 
    ISSN: 1349-9432
    Schlagwort(e): semiconductor laser ; optical feedback ; low frequency fluctuation ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The properties of low-frequency fluctuations in semiconductor lasers with optical feedback from a long external cavity are experimentally studied. Frequency-locking of the laser light output to the injection current modulation is observed when the modulation frequency approaches the external cavity mode. The modulation frequency for the successful frequency-locking is always less than the external cavity mode frequency and the locking domains as a function of the modulation amplitude is asymmetric with respect to the frequency detuning.
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Cellular and molecular life sciences 45 (1989), S. 363-365 
    ISSN: 1420-9071
    Schlagwort(e): Dictyostelium discoideum ; cAMP oscillations ; biological rhythms ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Summary We have tested the light-scattering properties of suspensions of theDictyostelium discoideum mutantHH201 derived from the mutantFr17. Previous studies indicated thatHH201 andFr17 possess highly irregular rhythmic properties which might represent aperiodic oscillations, i.e. chaos. We report that the former mutant can display regular oscillatory behavior. Possible explanations for this result are discussed, including that of a transition from chaotic to periodic behavior resulting from some parameter change or from strong intercellular coupling in cell suspensions.
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Pure and applied geophysics 147 (1996), S. 729-744 
    ISSN: 1420-9136
    Schlagwort(e): Volcanic tremor ; intermittency ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract Harmonic tremor is widely studied and modelled in a very narrow frequency band (1–5 Hz) which represents the eigenfrequencies of a resonator assumed as the source of the phenomenon. Minimal effort was dedicated towards understanding its behaviour in larger temporal scales. Here we characterise the dynamic behaviour of volcanic tremor while evaluating the complete spectrum of the generalised dimension of the phase space. The starting time series constitutes the tremor amplitude picked every 10 minutes. The choice of this lag time is made on the basis of a qualitative analysis of the properties of the tremor. The results show intermittent behaviour of the dynamics which requires an 8-dimensional map to be completely described. An interesting result is that the maximum clustering of point density in phase space occurs in a monodimensional space which implies a periodicity sometimes observed experimentally. An appropriate predictive model needs more constraints on the nature of the eight variables involved in the process.
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Space science reviews 85 (1998), S. 141-158 
    ISSN: 1572-9672
    Schlagwort(e): equation of state ; opacity ; helium abundance ; lithium abundance ; tachocline ; solar neutrinos ; helioseismology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Standard solar models, although they are free from the influence of much of the fluid motion that is bound to be present in the Sun, have been shown by helioseismology to represent the spherically averaged structure of the Sun amazingly well. This state of affairs has come about after painstaking refinements by a great many people of the pertinent microphysics, including that which controls the equation of state, the opacity, the nuclear reaction rates and the diffusion that inhibits gravitational segregation of chemical elements. It has instilled confidence in the modellers in being able to predict the composition of the solar interior. But there are consequences of the flow, related particularly to redistribution of chemical species, that can be difficult to identify observationally, yet which may degrade any inferences we might make. Their potential presence must at least be acknowledged by anyone who tries to asses the reliability of the models. This report summarizes the discussions in the preceding pages of this volume of the current theoretical and observational status of the subject, pointing to many of the caveats that have been raised, and attempting at the same time to put them into a seemingly coherent discourse in the context of our present understanding of the workings of the solar interior.
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 39 (1985), S. 477-491 
    ISSN: 1572-9613
    Schlagwort(e): Solar activity ; magnetic cycles ; dynamos ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Slowly rotating main-sequence stars with deep convective zones have activity cycles like the sun's. The solar cycle is aperiodic and modulated to give intervals of reduced activity. A simple sixth-order system, obtained by truncating the dynamo equations, has solutions that mimic this behavior. The transition to chaos is analyzed and the astrophysical significance of these results is discussed.
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 43 (1986), S. 479-488 
    ISSN: 1572-9613
    Schlagwort(e): Homoclinic orbit ; Heteroclinic orbit ; bifurcations ; chaos ; Lorenz equations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The local bifurcation structure of a heteroclinic bifurcation which has been observed in the Lorenz equations is analyzed. The existence of a particular heteroclinic loop at one point in a two-dimensional parameter space (a “T point”) implies the existence of a line of heteroclinic loops and a logarithmic spiral of homoclinic orbits, as well as countably many other topologically more complicatedT points in a small neighborhood in parameter space.
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  • 20
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    Digitale Medien
    Springer
    Journal of statistical physics 46 (1987), S. 789-794 
    ISSN: 1572-9613
    Schlagwort(e): Cellular automata ; Kauffman model ; chaos ; phase transition ; percolation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The phase transition between frozen and chaotic behavior in Kauffman's cellular automata on a nearest neighbor square lattice does not agree with the percolation threshold of the forcing functions.
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  • 21
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    Digitale Medien
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    Journal of statistical physics 53 (1988), S. 1299-1314 
    ISSN: 1572-9613
    Schlagwort(e): Lyapunov ; scaling ; chaos ; nonlinear dynamics ; billiard ; gravity ; random matrix
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We consider the motion of a point particle (billiard) in a uniform gravitational field constrained to move in a symmetric wedge-shaped region. The billiard is reflected at the wedge boundary. The phase space of the system naturally divides itself into two regions in which the tangent maps are respectively parabolic and hyperbolic. It is known that the system is integrable for two values of the wedge half-angleθ 1 andθ 2 and chaotic forθ 1〈θ〈θ 2. We study the system at three levels of approximation: first, where the deterministic dynamics is replaced by a random evolution; second, where, in addition, the tangent map in each region is, replaced by its average; and third, where the tangent map is replaced by a single global average. We show that at all three levels the Lyapunov exponent exhibits power law behavior nearθ 1 andθ 2 with exponents 1/2 and 1, respectively. We indicate the origin of the exponent 1, which has not been observed in unaccelerated billiards.
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 54 (1989), S. 893-913 
    ISSN: 1572-9613
    Schlagwort(e): p-adic numbers ; dynamical systems ; chaos ; quasiperiodicity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The quadratic map overp-adic numbers is studied in some detail. We prove that near almost all indifferent fixed points it is topologically conjugate to a quasiperiodic linear map. We also establish the existence of chaotic behavior and describe it using symbolic dynamics.
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 54 (1989), S. 925-948 
    ISSN: 1572-9613
    Schlagwort(e): Symmetry breaking ; chaos ; band splitting ; crisis ; piecewise linear map
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A new type of crisis is shown to exist in a broad class of systems (including the Lorenz model) which leads to an anomalous band splitting or to a symmetry-breaking bifurcation of the strange attractor, depending on the actual values of the control parameters. A piecewise linear model is used to understand the mechanism of this crisis and to obtain exact results.
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  • 24
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    Digitale Medien
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    Journal of statistical physics 8 (1973), S. 299-307 
    ISSN: 1572-9613
    Schlagwort(e): Statistical thermodynamics of curved boundary layers ; scaled particle theory ; equation of state ; cycle equation ; fluid-solid phase transition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The thermodynamics of curved boundary layers, with the assumption that the distance between the surface of a fluid cavity and its surface of tension is a quadratic function of the cavity radius, is applied to the exact thermo-dynamic expression forG, the central function of scaled particle theory. The coefficients in the quadratic representation are determined so as to satisfyall five of the known exact conditions onG valid for cavity radii between one-half and one molecular diameter. The results of the calculation are displayed as the hard-sphere equation of state, the boundary tension associated with the surface of tension, and the distance between the cavity surface and the surface of tension. Although the hard-sphere equation of state obtained by this method using all five conditions onG is more accurate than in the case where only two or three conditions are used, the original scaled particle theory, in whichG itself was represented simply by a quadratic function of inverse powers of cavity radius, still yields the more accurate equation of state. Nevertheless, the present approach limits approximations to the distance between the cavity surface and the surface of tension, a small quantity in itself. The path to a still more improved theory remains well defined, contingent upon the discovery of additional exact conditions, and does not depend, as in the original scaled particle theory, on a form forG arrived at in a somewhat ad hoc manner.
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 81 (1995), S. 761-775 
    ISSN: 1572-9613
    Schlagwort(e): Logistic map ; diffusion ; Fisher equation ; chaos ; oscillations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The dynamics of a biological population governed by a modified Fisher equation is studied by means of Monte Carlo simulations. Reproduction of the population occurs at discrete times, while transport caused by diffusion and conduction takes place on shorter time scales. The discrete reproduction, modeled with a set of coupled logistic maps, exhibits phenomena which are not evident in the usual continuum version of the Fisher equation. Several mechanisms for biennial oscillations of the total population are investigated. One of these shows an ordered coupling between random diffusive motion and the chaotic attractor of the logistic map.
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 88 (1997), S. 807-824 
    ISSN: 1572-9613
    Schlagwort(e): Billiards ; Kolmogorov–Sinai entropy ; Lyapunov exponents ; ergodic theory ; chaos ; numerical experiments
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We perform new experiments on the Kolmogorov–Sinai entropy, Lyapunov exponents, and the mean free time in billiards. We study their dependence on the geometry of the scatterers made up of two interpenetrating square lattices, each one with circular scatterers with different radius. We find, in particular, that the above quantities are continuous functions of the ratio of the scatterer radius. However, it seems that their derivative is discontinuous around the radius ratio which separates the diffusive and nondiffusive types of geometries.
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 93 (1998), S. 833-842 
    ISSN: 1572-9613
    Schlagwort(e): Shell models ; turbulence ; chaos ; Lyapunov exponent ; conserved quantities ; shell maps
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study the chaotic behavior of the GOY shell model by measuring the variation of the maximal Lyapunov exponent with the parameter ε which determines the nature of the second invariant (the generalized “helicity” invariant). After a Hopf bifurcation, we observe a critical point at ε c ∼0.38704 above which the maximal Lyapunov exponent grows nearly linearly. For high values of ε the evolution becomes regular again, which can be explained by a simple analytic argument. A model with few shells shows two transitions. To simplify the model substantially we introduce a shell map which exhibits similar properties as the GOY model.
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 95 (1999), S. 867-902 
    ISSN: 1572-9613
    Schlagwort(e): kinetics of phase transitions ; domain coarsening ; asymptotic behavior ; self-similarity ; stability ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The classical Lifshitz–Slyozov–Wagner theory of domain coarsening predicts asymptotically self-similar behavior for the size distribution of a dilute system of particles that evolve by diffusional mass transfer with a common mean field. Here we consider the long-time behavior of measure-valued solutions for systems in which particle size is uniformly bounded, i.e., for initial measures of compact support. We prove that the long-time behavior of the size distribution depends sensitively on the initial distribution of the largest particles in the system. Convergence to the classically predicted smooth similarity solution is impossible if the initial distribution function is comparable to any finite power of distance to the end of the support. We give a necessary criterion for convergence to other self-similar solutions, and conditional stability theorems for some such solutions. For a dense set of initial data, convergence to any self-similar solution is impossible.
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  • 29
    Digitale Medien
    Digitale Medien
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    Journal of statistical physics 40 (1985), S. 371-395 
    ISSN: 1572-9613
    Schlagwort(e): Dynamical systems ; nonlinear dynamics ; chaos ; turbulence ; intermittent turbulence ; intermittency ; noise ; external noise ; fluctuations ; external fluctuations ; Ginzburg-Landau equation ; amplitude equation ; spatially growing waves ; convective instability ; spatial instability ; secondary instability ; noise-sustained structure ; noise amplification ; spatial noise amplification ; pattern formation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The time-dependent generalized Ginzburg-Landau equation is an equation that is related to many physical systems. Solutions of this equation in the presence of low-level external noise are studied. Numerical solutions of this equation in thestationary frame of reference and with anonzero group velocity that is greater than a critical velocity exhibit a selective spatial amplification of noise resulting in spatially growing waves. These waves in turn result in the formation of a dynamic structure. It is found that themicroscopic noise plays an important role in themacroscopic dynamics of the system. For certain parameter values the system exhibits intermittent turbulent behavior in which the random nature of the external noise plays a crucial role. A mechanism which may be responsible for the intermittent turbulence occurring in some fluid systems is suggested.
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 42 (1986), S. 509-521 
    ISSN: 1572-9613
    Schlagwort(e): Hard sphere fluid ; wall-atom distribution function ; wall contact values ; equation of state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Utilizing the integral equation approach to the hard sphere fluid system developed in the preceding paper, the hard sphere-hard wall interaction is studied. For the case of a flat wall, perturbation solutions of the integral equation valid to second and third order in the packing fraction,y, are derived. For a surface of arbitrary curvature, an equation of state valid to second order in the packing fraction is also derived. When applied to very small cavities, it is found that the pressure at high densities is significantly higher than it would be for a flat wall.
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  • 31
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 43 (1986), S. 369-390 
    ISSN: 1572-9613
    Schlagwort(e): Nonlinear dynamics ; circle map ; period doubling bifurcations ; chaos ; invariant measures ; average Lyapunov exponents ; path integrals
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The circle map provides a generic model for the response of damped, nonlinear oscillators to periodic perturbations. As the parameters are varied this dynamical system exhibits transitions from regular, ordered behavior to chaos. In this paper the regular and irregular behavior of the circle map are examined for a broad range of nonlinearities and frequencies which span not only the regular and transition regimes, which have been studied extensively, but also the strongly nonlinear, chaotic regime. We discuss the bistable behavior (split bifurcations) associated with maps with multiple extrema that gives rise to two disjoint attractors which can be periodic or chaotic and to the low order periodic orbits emerging from chaos via tangent bifurcations. To describe the chaotic behavior we use a statistical description based on a path integral formulation of classical dynamics. This path integral method provides a convenient means of calculating statistical properties of the nonlinear dynamics, such as the invariant measure of the average Lyapunov exponent, which in many cases reduce to analytic expressions or to numerical calculations which can be completed in a fraction of the time required to explicitly iterate the map.
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  • 32
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 52 (1988), S. 1389-1412 
    ISSN: 1572-9613
    Schlagwort(e): Bridge function ; tail function ; cavity functions ; hard-sphere fluids ; second zero-separation theorem ; self-consistent theory ; equation of state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A theorem for convolution integrals is proved and then applied to extend the “second zero-separation theorem” to the bridge functionb(r) and direct-correlation tail functionsd(r). This theorem allows us to exactly relate∂b(r)/∂r and∂d(r)/∂ratr=0 for the hard-sphere fluid to the “contact value” of the radial distribution functiong(r) atr=σ +. From this we obtain immediately the exact values of ∂b(r)/∂r and ∂d(r)/∂r atr=0 through second order in number density ρ. Using our results to compare the exact and Percus-Yevick (PY) bridge function, we find that they differ significantly. After obtaining the bridge function and tail function and their derivatives atr=0 andr=σ through, we suggest new approximations forb(0) andd(0) as well as an analytical integral-equation theory to improve the PY approximation in the pure hard-sphere fluid. The major deficiency of that approximation has been its poor assessment of the cavity function inside the hard-core region. Our theory remedies this defect in a way that yields ay(r) that is self-consistent with respct to the virial and compressibility relations and also the two zero-separation relations involvingy(r) and its spatial derivative atr=0.
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  • 33
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 48 (1987), S. 151-199 
    ISSN: 1572-9613
    Schlagwort(e): Homoclinic tangency ; bifurcation theory ; periodic attractors ; chaos ; hyperbolic repellor ; symbolic dynamics ; chemical thermokinetics ; cool flame-ignition oscillations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Nonlinear autonomous dynamical systems with ahomoclinic tangency to a periodic orbit are investigated. We study the bifurcation sequences of the mixed-mode oscillations generated by the homoclinicity, which are shown to belong to two different types, depending on the nature of the Liapunov numbers of the basic periodic orbit. A detailed numerical analysis is carried out to show how the existence of a tangent homoclinic orbit allows us to understand in a quantitative way a particular and regular sequence of cool flame-ignition oscillations observed in a thermokinetic model of hydrocarbon oxidation. Chaotic cool flame oscillations are also observed in the same model. When the control parameter crosses a critical value, this chaotic set of trajectories becomes globally unstable and forms a Cantor-like hyperbolic repellor, and the ignition mechanism generates ahomoclinic tangency to the Cantor set of trajectories. The complex bifurcation diagram may be globally reconstructed from a one-dimensional dynamical system, thanks to the strong contractivity of thermokinetics. It is found that a symbolic dynamics with three symbols is necessary to classify the periodic windows of the complex bifurcation sequence observed numerically in this system.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 48 (1987), S. 959-975 
    ISSN: 1572-9613
    Schlagwort(e): Belousov-Zhabotinsky system ; chemical oscillations ; dissipative structures ; diffusion instabilities ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A mechanism and a model of a ferroin-catalyzed oscillating chemical system are descrined. This reaction presents an excellent example of a far-from-equilibrium system that forms spatial and temporal dissipative structures. The model shows that while the well-stirred system has a unique and stable stationary state, the same reagent spread in a thin layer may form complex spatiotemporal paterns. Stationary periodic patterns of both small and large amplitude, standing waves, and inhomogeneous chaotic oscillations are found in the model.
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  • 35
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 48 (1987), S. 977-990 
    ISSN: 1572-9613
    Schlagwort(e): Nonlinear dynamics ; chaos ; crisis ; Belousov-Zhabotinskii reaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract An abrupt transition that has the character of aninterior crisis was observed in an experiment on the Belousov-Zhabotinskii reaction as a control parameter was varied (a crisis is a qualitative change in the dynamics of a system observed when an attractor collides with the stable manifold of a fixed point). The interpretation of the observed behavior as a crisis is corroborated by a numerical analysis of a seven-variable model of the reaction. The waveforms, attractors, and maps obtained in the simulation are remarkably similar to those obtained in the laboratory experiment. The simulation indicates that the crisis is a consequence of a multivalued first return map.
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  • 36
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 48 (1987), S. 1269-1282 
    ISSN: 1572-9613
    Schlagwort(e): Mixmaster model ; ergodic theory ; chaos ; Einstein equations ; cosmological singularity ; Kaluza-Klein cosmology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The topological dynamics of the mixmaster models in space-time dimension d+1 are investigated. We use a new parametrization to reduce the mixmaster map to a translation combined with an appropriate isometry or a dilating inversion. For d⩽9, we show that the mixmaster map is ergodic and topologically mixing. For d⩾10, the mixmaster map reduces to the identity after a finite number of iterations, except for a set of initial data with zero Lebesgue measure.
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  • 37
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 49 (1987), S. 511-550 
    ISSN: 1572-9613
    Schlagwort(e): Ergodicity ; time-dependent Hamiltonian ; decay of correlations ; adiabatic invariant ; billiard ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract For a “slowly” time-dependent Hamiltonian system exhibiting chaotic motion that ergodically covers the energy surface, the phase space volume enclosed inside this surface is an adiabatic invariant. In this paper we examine, both numerically and theoretically, how the error in this “ergodic adiabatic invariant” scales with the slowness of the time variation of the Hamiltonian. It is found that under certain circumstances, the error is diffusive and scales likeT −1/2, whereT is the characteristic time over which the Hamiltonian changes. On the other hand, for other cases (where motion in the Hamiltonian has a long-time 1/t tail in a certain correlation function), the error scales like [T −1 ln(T)]1/2. Both of these scalings are verified by numerical experiments. In the situation where invariant tori exist amid chaos, the motion may not be fully ergodic on the entire energy surface. The ergodic adiabatic invariant may still be useful in this case and the circumstances under which this is so are investigated numerically (in particular, the islands have to be small enough).
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  • 38
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 78 (1995), S. 1571-1589 
    ISSN: 1572-9613
    Schlagwort(e): Boltzmann ; ergodicity ; irreversibility ; Ruelle principle ; SRB measures ; chaos ; nonequilibrium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The contents of a not too well-known paper by Boltzmann are critically examined. The etymology of the word ergodic and its implications are discussed. A connection with the modern theory of Ruelle is attempted.
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  • 39
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 80 (1995), S. 481-485 
    ISSN: 1572-9613
    Schlagwort(e): Genericity ; chaos ; topological entropy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We prove the existence of an open and dense subset of mapsfεDiff ω ∞ (S2) which have positive topological entropy. It follows that these maps have infinitely many hyperbolic periodic points and an exponential growth rate of hyperbolic periodic points. The proof is an application of Pixton's theorem
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  • 40
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 82 (1996), S. 1099-1112 
    ISSN: 1572-9613
    Schlagwort(e): Ising model with long-range interactions ; Sierpiński-gasket lattice ; correlation functions ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A class of multispin correlation functions of an Ising model with ferromagnetic nearest neighbor interactionsK and constant (distance-independent) long-range interactionsQ 1=Q,l=1,2,..., on the Sierpiński-gasket lattice is considered. Using an exact method for calculating thermodynamic functions of hierarchically constructed Ising systems, it is shown that, for a set of values ofQ and for almost all values ofK, someM k-spin correlation functions, whereM k=3 k +3 withk=1,2,...,n andn=1,2,... being the order of lattice construction, change chaotically asn, k, and therebyM k increase to infinity. Accordingly, in the thermodynamic limit, these correlation functions prove to be nonanalytic for appropriate values ofQ andK. SinceM k-point correlation functions withk being finite, i.e., correlation functions involving finite numbers of spins, remain analytic asn tends to infinity, there is a smooth crossover between analytic properties of correlation functions of the two types.
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  • 41
    Digitale Medien
    Digitale Medien
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    Journal of statistical physics 85 (1996), S. 25-40 
    ISSN: 1572-9613
    Schlagwort(e): Glivenko-Cantelli theorem ; fractal ; almost sure convergence ; moment estimators ; least square estimators ; dynamical systems ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The Grassberger-Procaccia (GP) empirical spatial correlation integral, which plays an important role in dimension estimation, is the proportion of pairs of points in a segment of an orbit of lengthn, of a dynamical system defined on a metric space, which are no more than a distancer apart. It is used as an estimator of the GP spatial correlation integral, which is the probability that two points sampled independently from an invariant measure of the system are no more than a distancer apart. It has recently been proven, for the case of an ergodic dynamical system defined on a separable metric spaceythat the GP empirical correlation integral converges a.s. to the GP correlation integral at continuity points of the latter asn→∞. It is shown here that for ergodic systems defined on ℜd with the “max” metric the convergence is uniform inr. Further, a simplified proof based on weak convergence arguments of the result in separable spaces is given. Finally, the Glivenko-Cantelli theorem is used to obtain ergodic theorems for both the moment estimators and least square estimators of correlation dimension.
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  • 42
    Digitale Medien
    Digitale Medien
    Springer
    Journal of statistical physics 87 (1997), S. 1287-1306 
    ISSN: 1572-9613
    Schlagwort(e): Association ; phase equilibrium ; statistical mechanics ; partition function ; chemical engineering ; equation of state ; chemical equilibrium ; cluster distribution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A systematic and fundamental approach to associating mixtures is presented. It is shown how the thermodynamic functions may be computed starting from a partition function based on the cluster concept such as occurs in chemical theory. The theory provides a basis for and an extension of the existing chemical theory of (continuous) association. It is applicable to arbitrary association schemes. Analysis of separate cases is not necessary. The assumptions that were made to allow the development were chosen such as to make the principle of reactivity valid. It is this same principle that links various theories: the chemical theory of continuous association, the lattice fluid hydrogen bonding model, and first-order perturbation theory. The equivalence between these theories in appropriate limits is shown in a general and rigorous way. The theory is believed to provide a practical framework for engineering modeling work. Binary interaction parameters can be incorporated. The association scheme is accounted for by a set of generic equations, which should facilitate robust implementation in computer programs.
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  • 43
    Digitale Medien
    Digitale Medien
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    Journal of statistical physics 87 (1997), S. 1253-1271 
    ISSN: 1572-9613
    Schlagwort(e): Lorentz lattice gases ; chaos ; thermodynamic formalism ; random walks ; localization transition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The thermodynamic formalism expresses chaotic properties of dynamical systems in terms of the Ruelle pressure ψ(β). The inverse-temperature-like variable β allows one to scan the structure of the probability distributin in the dynamic phase space. This formalism is applied here to a lorentz lattice gas. where a particle moving on a lattice of sizeL d collides with fixed scatterers placed at random locations. Here we give rigorous arguments that the Ruelle pressure in the limit of infinite systems has two branches joining with a slope discontinuity at β=1. The low- and high-β branches correspond to localization of trajectories on respectively the “most chaotic” (highest density) region and the “most deterministic” (lowest density) region, i.e. ψ(β) is completely controlled by rare fluctuations in the distribution of scatterers on the lattice. and it dose not carry and information on the global structure of the static disorder. As β approaches unity from either side, a localization-delocalization transition leads to a state where trajectories are extended and carry information on transprot properties. At finiteL the narrow region around β=1 where the trajectories are extended scales as (InL)−2. where α depends on the sign of 1−β, ifd〉1, and as (L InL)−1 ifd=1. This result appears to be general for diffusive systems with static disorder, such as random walks in random environments or for the continuous Lorentz gas. Other models of random walks on disordered lattices, showing the same phenomenon, are discussed.
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  • 44
    Digitale Medien
    Digitale Medien
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    Journal of statistical physics 92 (1998), S. 909-972 
    ISSN: 1572-9613
    Schlagwort(e): Perturbation theory ; Hamiltonian dynamics ; wave–particle interaction: transport properties ; chaos ; plasma turbulence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The dynamics defined by the Hamiltonian $$H = p^2 /2 + A\sum\nolimits_{m = - M}^M {\cos (q - mt + \varphi m)}$$ , where the φ m are fixed random phases, is investigated for large values of A, and for $$M \gg A^{2/3}$$ . For a given P * and for $$\Delta \upsilon \geqslant A^{2/3}$$ , this Hamiltonian is transformed through a rigorous perturbative treatment into a Hamiltonian where the sum of all the nonresonant terms, having a Q dependence of the kind cos(kQ − nt + φ m) with $$|n/k - P^ * | 〉 \Delta \upsilon$$ , is a random variable whose r.m.s. with respect to the φ m is exponentially small in the parameter $$\varepsilon = A/\Delta \upsilon ^{3/2}$$ . Using this result, a rationale is provided showing that the statistical properties of the dynamics defined by H, and of the reduced dynamics including at each time t only the terms in H such that $$|m - p(t)| \leqslant \alpha A^{2/3}$$ , can be made arbitrarily close by increasing α. For practical purposes α close to 5 is enough, as confirmed numerically. The reduced dynamics being nondeterministic, it is thus analytically shown, without using the random-phase approximation, that the statistical properties of a chaotic Hamiltonian dynamics can be made arbitrarily close to that of a stochastic dynamics. An appropriate rescaling of momentum and time shows that the statistical properties of the dynamics defined by H can be considered as independent of A, on a finite time interval, for A large. The way these results could generalize to a wider class of Hamiltonians is indicated.
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  • 45
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    Digitale Medien
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    Landscape ecology 11 (1996), S. 107-113 
    ISSN: 1572-9761
    Schlagwort(e): scaling ; temporal patterns ; equilibrium ; stability ; succession ; predictability ; variability ; grassland ; savannah ; chaos ; ecological scale ; vegetation dynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Longterm (45 years) temporal data were used to assess the influence of spatial scale on temporal patterns of a semi-arid west Texas grassland. Temporal basal area dynamics of common curlymesquite (Hilaria belangeri (Steud.) Nash) collected from permanent plots within two areas that were released from disturbance (longterm overgrazing and drought), were evaluated at two spatial scales (quadrat, site). Wiens (1989) proposed hypotheses to characterize the influence of scale on variability, predictability, and equilibrium. These hypotheses were tested for this grassland and temporal patterns observed were different for each spatial scale. The large scale (site) was characterized by low variation between units, high variation within units, high potential predictability, and possible movement toward a fluctuating but relatively stable or equilibrial state. At the small scale (quadrat), variation between units was high, predictability low, and there was no indication of movement toward a stable state; chaotic behavior may be expressed at this scale although the length of the temporal record may not be sufficient to evaluate this phenomenon.
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  • 46
    Digitale Medien
    Digitale Medien
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    Il nuovo cimento della Società Italiana di Fisica 18 (1996), S. 765-770 
    ISSN: 0392-6737
    Schlagwort(e): Solitons ; chaos ; Solitons ; BGK modes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Summary A new dromion solution is obtained for a (2+1)-dimensional integrable model: the Davey-Stewartson equation. Some interesting questions which emerge in the procedure of getting the solution are also discussed.
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  • 47
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    Digitale Medien
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    Optical review 6 (1999), S. 365-371 
    ISSN: 1349-9432
    Schlagwort(e): semiconductor laser ; optical feedback ; chaos ; relaxation oscillation ; coherence collapse
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The dynamic characteristics of a semiconductor laser with optical feedback are strongly dependent on the injection current and the reflectivity and position of the external feedback reflector. We investigated the relaxation oscillation enhancement and coherence collapse state of the laser oscillation based on the laser rate equations. It is well known that laser output power jumps with increase of the injection current due to external mode transition. But here for the first we time demonstrate the existence of a chaotic scenario within successive laser power jumps. The results calculated by numerical simulations based on the rate equations are compared with those of the experiments and good coincidence between them is found.
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  • 48
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    Digitale Medien
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    Acta mechanica solida Sinica 10 (1997), S. 316-321 
    ISSN: 0894-9166
    Schlagwort(e): continuous dynamical system ; chaos ; parametric open-plus-closed-loop control ; the Lorenz model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract This paper presents a parametric open-plus-closed-loop control approach to controlling chaos in continuous dynamical systems. As an example, chaos in the Lorenz model is controlled to demonstrate its application. Finally, the relations between the parametric open-plus-closed-loop control and the former control methods, such as the open-plus-closed-loop control and the parametric entrainment control, are discussed.
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  • 49
    Digitale Medien
    Digitale Medien
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    Acta mechanica solida Sinica 10 (1997), S. 262-275 
    ISSN: 0894-9166
    Schlagwort(e): global bifurcation ; chaos ; nonlinear vibration ; basin ; fractal
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The global bifurcation and chaos are investigated in this paper for a van der Pol-Duffing-Mathieu system with a single-well potential oscillator by means of nonlinear dynamics. The autonomous system corresponding to the system under discussion is analytically studied to draw all global bifurcation diagrams in every parameter space. These diagrams are called basic bifurcation ones. Then fixing parameter in every space and taking the parametrically excited amplitude as a bifurcation parameter, we can observe how to evolve from a basic bifurcation diagram to a chaos pattern in terms of numerical methods. The results are sufficient to show that the system has distinct dynamic behavior. Finally, the properties of the basins of attraction are observed and the appearance of fractal basin boundaries heralding the onset of a loss of structural integrity is noted in order to consider how to control the extent and the rate of the erosion in the next paper.
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  • 50
    Digitale Medien
    Digitale Medien
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    Physics and chemistry of minerals 26 (1999), S. 644-648 
    ISSN: 1432-2021
    Schlagwort(e): Key words MnO ; CdO ; rock-salt monoxides ; X-ray diffraction ; equation of state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: Abstract Room-temperature volume measurements up to 8.1 GPa reveal that rock-salt structured MnO and CdO have identical compressibility in the pressure range studied. In the plot of bulk modulus vs unit-cell volume, CdO plots well above the trend of the 3d transition metal monoxides, a behavior that deviates from empirical predictions of constant K 0 V 0. The present observations are in favor of our earlier suggestion that, for isostructural solids, the empirically predicted bulk modulus-volume relationship may be limited to their subsets that share the same valence electron character (i.e., s vs 3d vs 4d). For cations forming transition metal monoxides, variations of Pauling electronegativity with ionic radius show differences that are qualitatively similar to the observed trends of bulk modulus, suggesting that bond covalency differences may contribute to the different behaviors between the 3d and 4d transition metal monoxides.
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  • 51
    Digitale Medien
    Digitale Medien
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    Physics and chemistry of minerals 14 (1987), S. 58-66 
    ISSN: 1432-2021
    Schlagwort(e): equation of state ; thermodynamic properties ; phase transformations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie , Physik
    Notizen: Abstract Thermal equations of state have been derived for polymorphic forms of SiO2 and values of $$\mathop \smallint \limits_0^P$$ V T dP have been tabulated. Available experimental data on the phase equilibria at high pressures and temperatures have been used with these equations to calculate the standard thermodynamic functions for the α-quartz-coesite and coesite-stishovite transformations. A study of sensitivity of calculated thermodynamical properties to uncertainties of phase equilibria data, initial data for elastic constants and equations of state has been carried out. The discrepancies between standard thermodynamic properties of these transformations calculated from phase equilibria data and solution calorimetry data still persist.
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  • 52
    Digitale Medien
    Digitale Medien
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    European biophysics journal 17 (1989), S. 273-280 
    ISSN: 1432-1017
    Schlagwort(e): Ventricular cardiocytes ; nonlinear dynamics ; chaos ; devil's staircase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Physik
    Notizen: Abstract We measured the non-linear dynamics of cardiac action potentials by varying the stimulation frequency from 2 to 20 Hz and obtained the following results: (i) When the fast Na+ current initiated the action potentials (‘fast action potentials’) periodicity was maintained, i.e. the pattern of action potentials repeated after a finite number of stimuli. Chaotic sequences were absent. The transition from one sequence to the next occurred as a devil's staircase. (ii) When, however, the slow Ca2+ current initiated the action potentials (‘slow action potentials’), we observed chaos, i.e. fully irregular behaviour, as well as bifurcations. (iii) Our results confirm the supposition that the global dynamics of cardiac cells can be well described by simple one-dimensional maps which predict these two kinds of behaviour.
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  • 53
    Digitale Medien
    Digitale Medien
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    Acta mechanica Sinica 12 (1996), S. 1-14 
    ISSN: 1614-3116
    Schlagwort(e): ellipticity ; hydrodynamic instabilities ; chaos ; phase transition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Ellipticity as the underlying mechanism for instabilities of physical systems is highlighted in the study of model nonlinear evolution equations with dissipation and the study of phase transition in Van der Waals fluid. Interesting results include spiky solutions, chaotic behavior in the context of partial differential equations, as well as the nucleation process due to ellipticity in phase transition.
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  • 54
    Digitale Medien
    Digitale Medien
    Springer
    Acta mechanica Sinica 11 (1995), S. 357-372 
    ISSN: 1614-3116
    Schlagwort(e): semi-analytical and semi-numerical method ; global bifurcations ; chaos ; van del Pol-Duffing-Mathieu system
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Semi-analytical and semi-numerical method is used to investigate the global bifurcations and chaos in the nonlinear system of a Van der Pol-Duffing-Mathieu oscillator. Semi-analytical and semi-numerical method means that the autonomous system, called Van der Pol-Duffing system, is analytically studied to draw all global bifurcations diagrams in parameter space. These diagrams are called basic bifurcation diagrams. Then fixing parameter in every space and taking parametrically excited amplitude as a bifurcation parameter, we can observe the evolution from a basic bifurcation diagram to chaotic pattern by numerical methods.
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  • 55
    Digitale Medien
    Digitale Medien
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    Acta mechanica Sinica 5 (1989), S. 361-368 
    ISSN: 1614-3116
    Schlagwort(e): average atom model ; equation of state ; Dirac-Slater equation ; pressure ionization effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Within the approximations of spherical lattice cell, central-field, and relativistic Fermi statistics, an algorithm with average atom model is presented to calculate the electronic energy levels and equation of state for hot and dense matter at arbitrary densities and temperatures. Choosing Zink's analytical potential as initial potential, we have solved the Dirac-Slater equation which satisfies the Weigner-Seitz boundary condition. The electronic energy bands are not taken into account. Taking energy level degeneracy as a continuous function of density, we have considered the pressure ionization effects for highly dense matter. Results for13Al atom are shown.
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  • 56
    Digitale Medien
    Digitale Medien
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    Acta mechanica Sinica 13 (1997), S. 106-112 
    ISSN: 1614-3116
    Schlagwort(e): faraday experiment ; chaos ; resonant interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Free surface waves in a cylinder of liquid under vertical excitation with slowly modulated amplitude are investigated in the current paper. It is shown by both theoretical analysis and numerical simulation that chaos may occur even for a single mode with modulation which can be used to explain Gollub and Meyer's experiment. The implied resonant mechanism accounting for this phenomenon is further elucidated.
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  • 57
    Digitale Medien
    Digitale Medien
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    Acta mechanica Sinica 16 (2000), S. 121-127 
    ISSN: 1614-3116
    Schlagwort(e): thermal convection flow ; transition ; chaos ; electron beam fluorescence technique
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Chaotic phenomena in the wake of thermal convection flow fields above a heating flat plate were investigated experimentally. A newly developed electron beam fluorescence technique (EBF) was used to simultaneously measure density fluctuation at 7 points in a cross section above the plate. Correlation dimensions, intermittence coefficients, Fourier spectrum have been obtained for different Grashof numbers. Spatial distribution of correlation dimensions are presented. The experimental result shows that there is a certain relationship between the density fluctuation and theGr number. And time-spacial characteristic of chaos evolution is also given.
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  • 58
    Digitale Medien
    Digitale Medien
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    Biology and philosophy 12 (1997), S. 327-340 
    ISSN: 1572-8404
    Schlagwort(e): mind architecture ; brain architecture ; computer metaphor ; chaos ; non-linear phenomena ; reductionism ; cognitive functionalism ; neurocomputation ; PDP ; knowledge process
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Philosophie
    Notizen: Abstract The use of the computer metaphor has led to the proposal of ’’mind architecture‘‘ (Pylyshyn 1984; Newell 1990) as a model of the organization of the mind. The dualist computational model, however, has, since the earliest days of psychological functionalism, required that the concepts ’’mind architecture‘‘ and ’’brain architecture‘‘ be remote from each other. The development of both connectionism and neurocomputational science, has sought to dispense with this dualism and provide general models of consciousness – a ’’uniform cognitive architecture‘‘ –, which is in general reductionist, but which retains the computer metaphor. This paper examines, in the first place, the concepts of mind architecture and brain architecture, in order to evaluate the syntheses which have recently been offered. It then moves on to show how modifications which have been made to classical functionalist mind architectures, with the aim of making them compatible with brain architectures, are unable to resolve some of the most serious problems of functionalism. Some suggestions are given as to why it is not possible to relate mind structures and brain structures by using neurocomputational approaches, and finally the question is raised of the validity of reductionism in a theory which sets out to unite mind and brain architectures.
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  • 59
    Digitale Medien
    Digitale Medien
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    Applied mathematics and mechanics 19 (1998), S. 625-635 
    ISSN: 1573-2754
    Schlagwort(e): shallow arch ; internal resonance ; steady state motion ; bifurcation ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Mathematik , Physik
    Notizen: Abstract The bifurcation dynamics of shallow arch which possesses initial deflection under periodic excitation for the case of 1∶2 internal resonance is studied in this paper. The whole parametric plane is divided into several different regions according to the types of motions; then the distribution of steady state motions of shallow arch on the plane of physical parameters is obtained. Combining with numerical method, the dynamics of the system in different regions, especially in the Hopf bifurcation region, is studied in detail. The rule of the mode interaction and the route to chaos of the system is also analysed at the end.
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  • 60
    Digitale Medien
    Digitale Medien
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    Applied mathematics and mechanics 20 (1999), S. 830-836 
    ISSN: 1573-2754
    Schlagwort(e): chaos ; Melnikov method ; Poincaré map ; phase portrait ; time-displacement diagram ; O343.5
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Mathematik , Physik
    Notizen: Abstract In this paper, the system of the forced vibration $$\ddot T - \lambda _1 T + \lambda _2 T^2 + \lambda _3 T^3 = \varepsilon \left( {g\cos \omega t - \varepsilon '\dot T} \right)$$ is discussed, which contains square and cubic items. The critical condition that the system enters chaotic states is given by the Melnikov method. By Poincaré map, phase portrait and time-displacement history diagram, whether the chaos occurs is determined.
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  • 61
    Digitale Medien
    Digitale Medien
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    Studia geophysica et geodaetica 42 (1998), S. 335-342 
    ISSN: 1573-1626
    Schlagwort(e): fast dynamo ; rotating convection ; chaos ; MHD
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Geologie und Paläontologie , Physik
    Notizen: Abstract As a step towards a physically realistic model of a fast dynamo, we study numerically a kinematic dynamo driven by convection in a rapidly rotating cylindrical annulus. Convection maintains the quasi-geostrophic balance whilst developing more complicated time-dependence as the Rayleigh number is increased. We incorporate the effects of Ekman suction and investigate dynamo action resulting from a chaotic flow obtained in this manner. We examine the growth rate as a function of magnetic Prandtl number Pm, which is proportional to the magnetic Reynolds number. Even for the largest value of Pm considered, a clearly identifiable asymptotic behaviour is not established. Nevertheless the available evidence strongly suggests a fast dynamo process.
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  • 62
    Digitale Medien
    Digitale Medien
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    Applied mathematics and mechanics 19 (1998), S. 67-73 
    ISSN: 1573-2754
    Schlagwort(e): Reyleigh number ; Lorenz system ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Mathematik , Physik
    Notizen: Abstract Controlling chaos in the Lorenz system with a controllable Rayleigh number is investigated by the state space exact linearization method. Based on proving the exact linearizability, the nonlinear feedback is utilized to design the transformation changing the original chaotic system into a linear controllable one so that the control is realized. Numerical examples of control are presented.
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  • 63
    Digitale Medien
    Digitale Medien
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    Applied mathematics and mechanics 21 (2000), S. 1008-1015 
    ISSN: 1573-2754
    Schlagwort(e): subharmonic bifurcation ; heteroclinic orbit ; chaos ; Melnikov function ; O34
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Mathematik , Physik
    Notizen: Abstract The dynamics behaviour of tension bar with periodic tension velocity was presented. Melnikov method was used to study the dynamic system. The results show that material nonlinear may result in anomalous dynamics response. The subharmonic bifurcation and chaos may occur in the determined system when the tension velocity exceeds the critical value.
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  • 64
    Digitale Medien
    Digitale Medien
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    Applied mathematics and mechanics 20 (1999), S. 360-364 
    ISSN: 1573-2754
    Schlagwort(e): buckled plate ; chaos ; Poincaré section
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Mathematik , Physik
    Notizen: Abstract The primary aim of this paper is to study the chaotic motion of a large deflection plate. Considered here is a buckled plate, which is simply supported and subjected to a lateral harmonic excitation. At first, the partial differential equation governing the transverse vibration of the plate is derived. Then, by means of the Galerkin approach, the partial differential equation is simplified into a set of two ordinary differential equations. It is proved that the double mode model is identical with the single mode model. The Melnikov method is used to give the approximate excitation thresholds for the occurrence of the chaotic vibration. Finally numerical computation is carried out.
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  • 65
    Digitale Medien
    Digitale Medien
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    Evolutionary ecology 11 (1997), S. 105-126 
    ISSN: 1573-8477
    Schlagwort(e): delayed reproduction ; evolutionarily stable strategy ; life history polymorphism ; population dynamics ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Behavioural and life history polymorphisms are often observed in animal populations. We analyse the timing of maturation and reproduction in risky and resource-limited environments. Field and laboratory evidence suggests that female voles and mice, for example, can adjust their breeding according to the level of risk to their own survival and to survival probabilities and recruitment of young produced under different environmental conditions. Under risky or harsh conditions breeding can be postponed until later in the current breeding season or even to the next breeding season. We develop a population dynamics and life history model for polymorphism in reproduction (co-existence of breeding and non-breeding behaviours) of females in an age-structured population, with two temporally distinct mating events within the breeding season. We assume that, after overwintering, the females can breed in spring and again in summer or they can delay breeding in spring and breed in summer only. Young females born in spring can either mature and breed in summer or stay immature and postpone breeding over the winter to the next breeding season. We show that an evolutionarily stable breeding strategy is either an age-structured combination of pure breeding behaviours (old females breed and young delay maturity) or a mixed breeding behaviour within age-classes (a fraction of females breed and the rest of the age class postpones breeding). Co-occurrence of mixed reproductive behaviour in spring and summer within a single breeding season is observed in fluctuating populations only. The reproductive patterns depend on intraspecific, possibly interspecific, and ecological factors. The density dependence (e.g. social suppression) and predation risk are shown to be possible evolutionary mechanisms in adjusting the relative proportions of the different but co-existing reproductive behaviours.
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  • 66
    Digitale Medien
    Digitale Medien
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    International journal of salt lake research 8 (1999), S. 55-70 
    ISSN: 1573-8590
    Schlagwort(e): Dead Sea ; equation of state ; pycnometry ; salinity ; saturation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geographie
    Notizen: Abstract Some widespread misconceptions about salinity are pointed out, explained and commented on. Definitions, units, and methods of salinity determination recommended for brines of moderate salinities may become unsuitable for highly saline brines. Various salinity units are examined and commented on, and density at a precisely monitored temperature is chosen as the preferable “substitute parameter” for salinity determination of hypersaline brines. It is shown that ambient air density during pycnometric measurements must be known as accurately as required of the brine's density, and that its value must be added to the direct pycnometric measurement. Variations of atmospheric pressure at the time of pycnometry must be taken into account if greater than 15 mB. For a salinity accuracy of ±0.02 per mille, as required for some physical and chemical studies, the temperature of the sample during salinity measurement must be monitored with an accuracy of at least 0.04°C. A definite curve in the ρ-S plane, corresponding to the conversion of salinity to density at a fixed temperature, andvice-versa, does not exist if the brine is saturated in one of its salts. Non-linearity in the equation of state is shown to affect the surface level drop due to evaporation; the effect is negligible at low salinities, but a 10 per cent correction is already required at the salinity found in the northern Red Sea (41 per mille). Reliable reference points for the conversion of absolute salinity to density of highly saline brines are not known, at present, as accurately as desirable; pending the accurate determination of such reference points, a substantial dilution of hypersaline brines (for the purpose of adapting them to conductivity measurements) would multiply the error range by more than a hundred fold. On the other hand, a minute dilution of hypersaline brine samples to prevent salt crystal formation is possible and would not bring about any major increase of the error range in their density (salinity) determination.
    Materialart: Digitale Medien
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  • 67
    Digitale Medien
    Digitale Medien
    Springer
    International journal of salt lake research 8 (1999), S. 55-70 
    ISSN: 1573-8590
    Schlagwort(e): Dead Sea ; equation of state ; pycnometry ; salinity ; saturation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geographie
    Notizen: Abstract Some widespread misconceptions about salinity are pointed out, explained and commented on. Definitions, units, and methods of salinity determination recommended for brines of moderate salinities may become unsuitable for highly saline brines. Various salinity units are examined and commented on, and density at a precisely monitored temperature is chosen as the preferable “substitute parameter” for salinity determination of hypersaline brines. It is shown that ambient air density during pycnometric measurements must be known as accurately as required of the brine's density, and that its value must be added to the direct pycnometric measurement. Variations of atmospheric pressure at the time of pycnometry must be taken into account if greater than 15 mB. For a salinity accuracy of ±0.02 per mille, as required for some physical and chemical studies, the temperature of the sample during salinity measurement must be monitored with an accuracy of at least 0.04°C. A definite curve in the ρ-S plane, corresponding to the conversion of salinity to density at a fixed temperature, and vice-versa, does not exist if the brine is saturated in one of its salts. Non-linearity in the equation of state is shown to affect the surface level drop due to evaporation; the effect is negligible at low salinities, but a 10 per cent correction is already required at the salinity found in the northern Red Sea (41 per mille). Reliable reference points for the conversion of absolute salinity to density of highly saline brines are not known, at present, as accurately as desirable; pending the accurate determination of such reference points, a substantial dilution of hypersaline brines (for the purpose of adapting them to conductivity measurements) would multiply the error range by more than a hundred fold. On the other hand, a minute dilution of hypersaline brine samples to prevent salt crystal formation is possible and would not bring about any major increase of the error range in their density (salinity) determination.
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  • 68
    ISSN: 1573-6873
    Schlagwort(e): electroreceptor ; catfish ; chaos ; unstable orbit ; periodic orbit ; sensory oscillator ; noise ; random process
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Medizin , Physik
    Notizen: Abstract We report the results of a search for evidence of periodic unstableorbits in the electroreceptors of the catfish. The function of thesereceptor organs is to sense weak external electric fields. Inaddition, they respond to the ambient temperature and to the ioniccomposition of the water. These quantities are encoded by receptorsthat make use of an internal oscillator operating at the level of themembrane potential. If such oscillators have three or more degreesof freedom, and at least one of which also exhibits a nonlinearity,they are potentially capable of chaotic dynamics. By detecting theexistence of stable and unstable periodic orbits, we demonstratebifurcations between noisy stable and chaotic behavior using theambient temperature as a parameter. We suggest that the techniquedeveloped herein be regarded as an additional tool for the analysisof data in sensory biology and thus can be potentially useful instudies of functional responses to external stimuli. We speculatethat the appearance of unstable orbits may be indicative of a stateof heightened sensory awareness by the animal.
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  • 69
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    Digitale Medien
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    Ecological research 13 (1998), S. 259-261 
    ISSN: 1440-1703
    Schlagwort(e): chaos ; complex dynamic ; insect population ; Tribolium castaneaum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Recently, the most convincing evidence of complex dynamics and chaos in biological populations has been presented for Tribolium castaneaum, a classic laboratory model insect. In this note, the robustness of this system is investigated and a constant immigration term is added to the adult population equation. It has been found that such perturbation to the model can either have a complicating effect (when the isolated system is periodic) or a simplifying one (when the system is chaotic in isolation).
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  • 70
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    Digitale Medien
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    Journal of seismology 2 (1998), S. 159-171 
    ISSN: 1573-157X
    Schlagwort(e): chaos ; dynamical systems ; Hurst exponent ; stochasticprocess ; time series
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract A procedure is presented for the analysis of complex stationary time series for which the Fourier power spectra reveals broadband noise or broadened pulses. We first determine the Hurst exponent from which we may know whether the time series under study is mainly random or if the data points present correlations. If the data are correlated, a chaotic analysis will reveal whether they may be interpreted as a low dimensional nonlinear system (defined by a low correlation dimension and a finite and positive Kolmogorov entropy and largest positive Lyapunov exponent) or as a stochastic process. We have studied three kind of temporal series: inter-event time series of infrasonic pulses recorded at Stromboli volcano, and, S-coda waves and microseisms, that have been recorded at the eastern Pyrenees. Results show that microseisms and Coda waves can be modeled as a low dimensional deterministic system, Correlation dimensions 2.3, 3.2, respectively. At the contrary infrasonic has resulted stochastic. This chaotic character can be attributed to the medium properties. Coda waves with scattering through a fractal distribution of scatters or to multiple reflection inside resonators (for example sedimentary basins) and microseisms as a propagation of wave guide of variable cross section which have the same temporal characteristics as a nonlinear forced oscillator.
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  • 71
    Digitale Medien
    Digitale Medien
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    Journal of seismology 3 (1999), S. 393-408 
    ISSN: 1573-157X
    Schlagwort(e): cepstrum ; chaos ; correlation dimension ; nonlinear oscillators
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract The discussion about the source of low frequency events generally wrecorded on active volcanoes is still open and needs deeper understanding of the phenomena involved in their generation. Most of the models view such a phenomenon as a source effect (oscillation of volcanic fluids in conduits or cracks), although a different explanation as a path or site effect exists. In the present paper we analysed 26 seismic signals recorded at Vulcano and 60 at Stromboli in order to put some constraints on the functional shape of the recorded signals. They evidence all the characteristics of the low frequency events. The spectral analysis reveals sharp peaks in the range 0.5–4 Hz, while the cepstra suggest that the signals are composed by a two-sine kind function. This suggestion is confirmed by the two-dimensional projections of the reconstructed phase space. The correlation dimension of the attractor is very close to 3 for both the volcanoes confirming the existence of a toroidal structure in the phase space. This implies that we can suggest as a model for the low frequency events source a physical mechanism very similar to a Duffing oscillator or any other quasiperiodic one. In particular in the cases of the analysed volcanoes we recognise two independent oscillations.
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  • 72
    ISSN: 1435-1528
    Schlagwort(e): Periodically forced spheroids ; chaos ; particle separation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract In this paper, we consider the technologically important problem of periodically forced spheroids in simple shear flow and demonstrate the existence of chaotic parametric regimes. The approach used by Strand (1989) (for the Strong Brownian limit) is inappropriate in the chaotic regimes corresponding to the weak Brownian limit. Our results also indicate a strong dependence of the solutions obtained on the aspect ratio of the spheroids. This strong dependence on the aspect ratio may be utilized to separate particles from a suspension of particles having different shapes but similar sizes.
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  • 73
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    Digitale Medien
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    Rheologica acta 28 (1989), S. 302-310 
    ISSN: 1435-1528
    Schlagwort(e): Composite ; thermalexpansivity ; interlayer model ; lattice model ; equation of state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract We continue the comparison of the results of an interlayer model, based on the theory of elastic continua, and a molecular model, derived from a theory of mixtures, previously presented in terms of bulk moduli K. We now derive expressions for the dependence of the thermal expansivityα c on the volume fractionφ f of the filler, at low and elevated values ofφ f . Correspondencies between the characteristic parameters, viz. adhesion and repulsion ratios on the one hand, and interlayer content and thermal properties of matrix, filler, and layer, on the other, are examined. Since in the molecular theory bothα andK are derived from an equation of state, the identical set of parameters determines both functions and suggests correlations between them.
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  • 74
    Digitale Medien
    Digitale Medien
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    Rheologica acta 25 (1986), S. 161-165 
    ISSN: 1435-1528
    Schlagwort(e): Filled composite ; bulk modulus ; lattice model ; equation of state ; interlayer model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Abstract Two models are compared. One is based on the theory of elastic continua, and describes the interaction between filler and matrix in terms of an interfacial layer of varying volume fraction and elastic properties. The other derives from an equation of state for the constituents and the composite, based on molecular considerations. The filler-matrix interaction is then expressed in terms of segmental attractions and repulsions. We examine the dependence of the bulk modulusK c (ϕ f ) on the volume fractionϕ f of filler and then show the correspondence between the two theories in terms of the infinite dilution limit of the ratio [K c (ϕ f ) −K m ]/(K m ϕ f ) where the indexm refers to the matrix.
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  • 75
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    Space science reviews 85 (1998), S. 49-60 
    ISSN: 1572-9672
    Schlagwort(e): helioseismology ; equation of state ; helium abundance ; excited states
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The equation of state is one of the three fundamental ingredients used to construct stellar models. The plasma of the interiors of stars such as the Sun is only slightly non-ideal. However, the extraordinary accuracy of the helioseismological data requires refined equations of state. It turned out to be necessary to include a Coulomb correction, commonly evaluated in the Debye-Hückel approximation. Higher-order non-ideal effects have implications as well, both for plasma physics and for solar physics. As a typical example, the recently studied thermodynamic consequence of excited states in compound particles is discussed. This effect is of considerable relevance in the helioseismic determination of the helium abundance in the solar convection zone.
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  • 76
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    Journal of biological physics 26 (2000), S. 77-83 
    ISSN: 1573-0689
    Schlagwort(e): Bacterial movement ; chaos ; cryptic growth cell ; proteusmirabilis ; turbulence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Physik
    Notizen: Abstract Our objective was to observe a new form of turbulence caused bybiological effects – biological micro-turbulence and explore itsprocess and controlling factors. The methods used were proteusmirabilis CGCs micro-cultured to render the occurrence of the specific movement on micro-organic suspension and its controllingfactors were determined by comparison with the control trials.The results showed that turbulence under the microscope was generally in a mass but partially regular. It was also confirmedthat the turbulence under the microscope exhibited hollow effect,temperature-dependent switching on of occurrence and self-controlof suspension quantity. It is clarified that this new form ofturbulence is a spontaneous and self-control process, which providesan experimental model with controllable conditions for studies ofturbulence and a new way for researches on the mechanism andphysiological functions of the flow of body liquid.
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  • 77
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    Digitale Medien
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    Celestial mechanics and dynamical astronomy 64 (1996), S. 243-260 
    ISSN: 1572-9478
    Schlagwort(e): Perturbative methods ; chaos ; resonance ; adiabatic invariant ; asteroids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A simple generalization of Wisdom's perturbative method, as originally proposed by Wisdom (1985), is obtained. Any number of resonant cosines can be handled and the method can also accommodate more involved disturbing functions. Averaged trajectories are easily obtained by drawing level curves of the action. Here, the method is first tested for simple models of 3:1 and 2:1 resonant problems. Comparisons with numerical integration and surface-section curves show very good agreements.
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  • 78
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    Digitale Medien
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    Journal of statistical physics 101 (2000), S. 649-663 
    ISSN: 1572-9613
    Schlagwort(e): limit cycle oscillations ; chaos ; periodic forcing ; entrainment ; model ; circadian rhythms
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Circadian rhythms occur in nearly all living organisms with a period close to 24 h. These rhythms constitute an important class of biological oscillators which present the characteristic of being naturally subjected to forcing by light-dark (LD) cycles. In order to investigate the conditions in which such a forcing might lead to chaos, we consider a model for a circadian limit cycle oscillator and assess its dynamic behavior when a light-sensitive parameter is periodically forced by LD cycles. We determine as a function of the forcing period and of the amplitude of the light-induced changes in the light-sensitive parameter the occurrence of various modes of dynamic behavior such as quasi-periodicity, entrainment, period-doubling and chaos. The type of oscillatory behavior markedly depends on the forcing waveform; thus the domain of entrainment grows at the expense of the domain of chaos as the forcing function progressively goes from a square wave to a sine wave. Also studied is the dependence of the phase of periodic or aperiodic oscillations on the amplitude of the light-induced changes in the control parameter. The results are discussed with respect to the main physiological role of circadian rhythms which is to allow organisms to adapt to their periodically varying environment by entrainment to the natural LD cycle.
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  • 79
    Digitale Medien
    Digitale Medien
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    Journal of statistical physics 101 (2000), S. 775-817 
    ISSN: 1572-9613
    Schlagwort(e): chaos ; diffusion ; Ehrenfest wind-tree model ; Lorentz gas ; statistical mechanics ; periodic orbits ; Brownian motion ; billiards ; time series analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We investigate the connections between microscopic chaos, defined on a dynamical level and arising from collisions between molecules, and diffusion, characterized by a mean square displacement proportional to the time. We use a number of models involving a single particle moving in two dimensions and colliding with fixed scatterers. We find that a number of microscopically nonchaotic models exhibit diffusion, and that the standard methods of chaotic time series analysis are ill suited to the problem of distinguishing between chaotic and nonchaotic microscopic dynamics. However, we show that periodic orbits play an important role in our models, in that their different properties in our chaotic and nonchaotic models can be used to distinguish them at the level of time series analysis, and in systems with absorbing boundaries. Our findings are relevant to experiments aimed at verifying the existence of chaoticity and related dynamical properties on a microscopic level in diffusive systems.
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  • 80
    Digitale Medien
    Digitale Medien
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    Journal of statistical physics 41 (1985), S. 125-173 
    ISSN: 1572-9613
    Schlagwort(e): Boolean functions ; chaos ; complexity ; delay equations ; difference equations ; discrete evolution equations ; dynamical systems ; nonlinear feedbacks and threshold behavior
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Boolean delay equations (BDEs) areevolution equations for a vector of discrete variables x(t). The value of each componentX i (t), 0 or 1. depends on previous values of all componentsx j (t− t ij ), x i (t)=f i (x1(t−t i1),...,x n (t −t in )). BDEs model the evolution of biological and physical systems with threshold behavior and nonlinear feedbacks. The delays model distinct interaction times between pairs of variables. In this paper, BDEs are studied by algebraic, analytic, and numerical methods. It is shown that solutions depend continuously on the initial data and on the delays. BDEs are classified intoconservative anddissipative. All BDEs with rational delays only haveperiodic solutions only. But conservative BDEs with rationally unrelated delays haveaperiodic solutions of increasing complexity. These solutions can be approximated arbitrarily well by periodic solutions of increasing period.Self-similarity andintermittency of aperiodic solutions is studied as a function of delay values, and certain number-theoretic questions related toresonances and diophantine approximation are raised. Period length is shown to be a lower semicontinuous function of the delays for a given BDE, and can be evaluated explicitly for linear equations. We prove that a BDE isstructurable stable if and only if it has eventually periodic solutions of bounded period, and if the length of initial transients is bounded. It is shown that, for dissipative BDEs, asymptotic solution behavior is typically governed by areduced BDE. Applications toclimate dynamics and other problems are outlined.
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  • 81
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    Digitale Medien
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    Journal of statistical physics 52 (1988), S. 1203-1220 
    ISSN: 1572-9613
    Schlagwort(e): Fluctuations ; spectra ; intensities ; statistical theories ; mixing ; chaos ; maximum entropy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Statistical considerations are applied to quantum mechanical amplitudes. The physical motivation is the progress in the spectroscopy of highly excited states, The corresponding wave functions are “strongly mixed.” In terms of a basis set of eigenfunctions of a zeroth-order Hamiltonian with good quantum numbers, such wave functions have contributions from many basis states. The vector x is considered whose components are the expansion coefficients in that basis. Any amplitude can be written as a†·x. It is argued that the components of x and hence other amplitudes can be regarded as random variables. The maximum entropy formalism is applied to determine the corresponding distribution function. Two amplitudes a†·x and b†·x are independently distributed if b†·a=0. It is suggested that the theory of quantal measurements implies that, in general, one can one determine the distribution of amplitudes and not the amplitudes themselves.
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  • 82
    Digitale Medien
    Digitale Medien
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    Journal of statistical physics 52 (1988), S. 1359-1365 
    ISSN: 1572-9613
    Schlagwort(e): High pressure ; equation of state ; krypton ; interatomic potential ; solid krypton ; many-body interactions ; Monte Carlo method
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The pressure-volume isotherm for krypton at 300 K is evaluated by the Monte Carlo method using pair and three-body potentials. The pair potentials used are that of Aziz and Slaman and a slightly modified version of their potential which gives better agreement with high-energy scattering data. The three-body potentials considered are the Axilrod-Teller interaction and the first-order three-body exchange interaction as parametrized by Loubeyre. The results are compared with recent measurements at pressures up to 300 kbar and the implications of the comparison are discussed. The best agreement with experiment is found using the Axilrod-Teller interaction as the only many-body interaction, indicating that the three-body exchange interaction is to a large extent canceled by higher many-body interactions, at least in the highly symmetrical environment of the crystal.
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  • 83
    Digitale Medien
    Digitale Medien
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    Journal of statistical physics 54 (1989), S. 495-514 
    ISSN: 1572-9613
    Schlagwort(e): Cellular automata ; mean-field theory ; statistical mechanics ; chaos ; dynamical systems ; lattice gas
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Local structure theory calculations7 are applied to the study of cellular automata on the two-dimensional hexagonal lattice. A particular hexagonal lattice rule denoted (3422) is considered in detail. This rule has many features in common with Conway'sLife. The local structure theory captures many of the statistical properties of this rule; this supports hypotheses raised by a study ofLife itself(6). As inLife, the state of a cell under (3422) depends only on the state of the cell itself and the sum of states in its neighborhood at the previous time step. This property implies that evolution rules which operate in the same way can be studied on different lattices. The differences between the behavior of these rules on different lattices are dramatic. The mean field theory cannot reflect these differences. However, a generalization of the mean field theory, the local structure theory, does account for the rule-lattice interaction.
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  • 84
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    Digitale Medien
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    Journal of statistical physics 54 (1989), S. 949-970 
    ISSN: 1572-9613
    Schlagwort(e): Relaxation oscillation ; stochastic perturbation ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract For relaxation oscillators stochastic and chaotic dynamics are investigated. The effect of random perturbations upon the period is computed. For an extended system with additional state variables chaotic behavior can be expected. As an example, the Van der Pol oscillator is changed into a third-order system admitting period doubling and chaos in a certain parameter range. The distinction between chaotic oscillation and oscillation with noise is explored. Return maps, power spectra, and Lyapunov exponents are analyzed for that purpose.
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  • 85
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    Digitale Medien
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    Journal of statistical physics 52 (1988), S. 527-569 
    ISSN: 1572-9613
    Schlagwort(e): Scaling ; thermodynamics ; period doubling ; mode locking ; dynamical systems ; chaos ; renormalization group
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Presentation functions provide the time-ordered points of the forward dynamics of a system as successive inverse images. They generally determine objects constructed on trees, regular or otherwise, and immediately determine a functional form of the transfer matrix of these systems. Presentation functions for regular binary trees determine the associated forward dynamics to be that of a period doubling fixed point. They are generally parametrized by the trajectory scaling function of the dynamics in a natural way. The requirement that the forward dynamics be smooth with a critical point determines a complete set of equations whose solution is the scaling function. These equations are compatible with a dynamics in the space of scalings which is conjectured, with numerical and intuitive support, to possess its solution as a unique, globally attracting fixed point. It is argued that such dynamics is to be sought as a program for the solution of chaotic dynamics. In the course of the exposition new information pertaining to universal mode locking is presented.
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  • 86
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    Journal of statistical physics 7 (1973), S. 143-159 
    ISSN: 1572-9613
    Schlagwort(e): Statistical thermodynamics of curved boundary layers ; scaledparticle theory ; equation of state ; cycle equation ; fluid-solid phase transition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The thermodynamics of curved boundary layers is combined with scaled particle theory to determine the rigid-sphere equation of state. In particular, the boundary analog of the Gibbs-Tolman-Koenig-Buff equation is solved for a rigid-sphere fluid, using the approximation that the distance between the surface of a cavity and its surface of tension is a function of the density only (the first-order approximation). This, in conjunction with several exact conditions onG, the central function of scaled particle theory, leads to an approximate rigid-sphere fluid equation of state and a qualitatively correct rigid-sphere solid equation of state. The fluid isotherm compares favorably with previous results (2.9 % error in the fourth virial coefficient), but due to the inaccuracy of the solid isotherm, no phase transition is obtained. The theory described here is to be contrasted with previous approaches in that a less arbitrary functional form forG is assumed, and the surface of tension and cavity surface are not assumed to be coincident. The “cycle equation” of Reiss and Tully-Smith is rederived by a simpler route and shown to be correct to all orders of cavity curvature, rather than only first order as was originally thought. A new exact condition, obtained from the compressibility equation of state, is used as a boundary condition for the “cycle equation” to determine the location of the equimolecular surface. This molecular calculation compares favorably (discrepancy of 〈2 %) with a thermodynamic calculation based on the boundary analog of the Gibbs adsorption equation and indicates the accuracy and consistency of the first-order approximation.
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  • 87
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    Journal of statistical physics 81 (1995), S. 869-880 
    ISSN: 1572-9613
    Schlagwort(e): Self-similarity ; self-affinity ; fractals ; scaling ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The general procedure of calculating fractal dimensions or other exponents is based on estimating some quantity as a function of scale and on assessing whether or not this function is a power law. This power law manifests itself in a log (quantity) versus log (scale) plot as a linear region (scaling). It has thus become the practice to estimate dimensions by the slope of some linear region in those log-log plots. When we are dealing with exact fractals (the Koch curve, for example) there are no problems. When, however, we are working with natural forms or observables, problems begin to emerge. In such cases the scaling region is subjectively estimated and often is only the result of the generic property of the quantity to increase monotonically or decrease monotonically as the scale goes to zero irrespective of the geometry of the object. Here we discuss these issues and suggest a procedure to deal with them.
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  • 88
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    Journal of statistical physics 83 (1996), S. 203-214 
    ISSN: 1572-9613
    Schlagwort(e): Quantum transport ; open billiards ; chaos ; Ericson fluctuation ; path-length spectrum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We report numerical results of an investigation of quantum transport for a weakly opened integrable circle and chaotic stadium billiards with a pair of conducting leads. While the statistics of spacings of resonance energies commonly follow the Wigner (GOE)-like distribution, the electric conductance as a function of the Fermi wavenumber shows characteristic noisy fluctuations associated with a typical set of classical orbits unique for both billiards. The wavenumber autocorrelation for the conductance is stronger in the stadium than the circle billiard, which we show is related to the length spectrum of classical short orbits. We propose an explanation of these contrasts in terms of the effect of phase decoherence due to the underlying chaotic dynamics.
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  • 89
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    Journal of statistical physics 88 (1997), S. 979-984 
    ISSN: 1572-9613
    Schlagwort(e): Fractal ; chaos ; Hausdorff dimension ; thermodynamic formalism ; strong-mixing ; outer measure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study the chaotic behavior of the Sierpinski carpet. It is proved that this dynamical system has a chaotic set whose Hausdorff dimension equals that of the Sierpinski carpet.
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  • 90
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    Journal of statistical physics 90 (1998), S. 749-765 
    ISSN: 1572-9613
    Schlagwort(e): Uncoupled logistic maps ; chaos ; fluctuations ; theoretical models ; computer simulations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Analytic approximations for the spatial average and its variance are derived for a system of N uncoupled chaotic logistic maps with growth parameter r = 4. The arising nontrivial closure problem is investigated with various techniques related to the classical moment problem. A Lyapunov-like linear stability analysis is presented for the transient as well as for the fluctuation regime.
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  • 91
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    Journal of statistical physics 96 (1999), S. 1163-1330 
    ISSN: 1572-9613
    Schlagwort(e): Coulomb ; plasma ; Saha ; screening ; Debye–Hückel ; virial ; equation of state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Results on the correlations of low-density classical and quantum Coulomb systems at equilibrium in three dimensions are reviewed. The exponential decay of particle correlations in the classical Coulomb system, Debye–Hückel screening, is compared and contrasted with the quantum case, where strong arguments are presented for the absence of exponential screening. Results and techniques for detailed calculations that determine the asymptotic decay of correlations for quantum systems are discussed. Theorems on the existence of molecules in the Saha regime are reviewed. Finally, new combinatoric formulas for the coefficients of Mayer expansions are presented and their role in proofs of results on Debye–Hückel screening is discussed.
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  • 92
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    Journal of statistical physics 96 (1999), S. 1343-1349 
    ISSN: 1572-9613
    Schlagwort(e): chaos ; fluctuation theorem ; large deviations ; chaotic hypothesis ; nonequilibrium statistical mechanics ; time reversal
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract An attempt is made to clarify the difference between a theorem derived by Evans and Searles in 1994 on the statistics of trajectories in phase space and a theorem proved by the authors in 1995 on the statistics of fluctuations on phase space trajectory segments in a nonequilibrium stationary state.
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  • 93
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    Journal of statistical physics 41 (1985), S. 249-261 
    ISSN: 1572-9613
    Schlagwort(e): Stochastic dynamics ; chaos ; Lyapunov exponents ; Monte Carlo ; critical phenomena
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract It is shown that stochastic equations can have stable solutions. In particular, there exists stochastic dynamics for which the motion is both ergodic and stable, so that all trajectories merge with time. We discuss this in the context of Monte Carlo-type dynamics, and study the convergence of nearby trajectories as the number of degrees of freedom goes to infinity and as a critical point is approached. A connection with critical slowdown is suggested.
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  • 94
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    Journal of statistical physics 38 (1985), S. 393-404 
    ISSN: 1572-9613
    Schlagwort(e): Incommensurate structure ; chaos ; nonlinear resonance ; magnetoelastic interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract To study equilibrium structures of magnetoelastic chains we have introduced an equivalent system and examined the whole class of its solutions. Appearance of various structures of the chain is due to the choice of an appropriate minimizing solution of the equivalent dynamic system. Commensurate and incommensurate structures, transitions from ferromagnetic to antiferromagnetic states, and transitions to the states with alternating clusters of ordered spins are obtained. Conditions for appearance of chaotic structures and amorphous magnetic states of the chain are discussed.
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  • 95
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    Journal of statistical physics 43 (1986), S. 489-519 
    ISSN: 1572-9613
    Schlagwort(e): Nonlinear dynamic systems ; coupled cells ; bifurcations ; dependence of solution on a parameter ; oscillations ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Dynamic behavior of two identical reaction cells with linear symmetric coupling is studied in detail. The standard model reaction scheme “Brusselator” is used as the description of the kinetics. The uncoupled cells can exhibit either a stable stationary state or stable periodic oscillations. A number of stationary and periodic oscillatory patterns arise as a result of the coupling. A non-homogeneous spatio-temporal organization includes homoclinic and heteroclinic oscillations as well as chaotic regimes. Numerical continuation algorithms are used to determine the dependence of stationary and periodic solutions on parameters. Stable stationary nonhomogeneous regimes exist typically at intermediate levels of coupling intensity. The nonhomogeneous periodic solutions arise either via Hopf bifurcatios from stationary solutions or via period-doubling bifurcations from the homogeneous periodic solutions. The results obtained may serve as a standard for the study of the behavior of other coupled systems in which either a stable stationary state or stable oscillations exist in the single cell.
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  • 96
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    Journal of statistical physics 56 (1989), S. 841-878 
    ISSN: 1572-9613
    Schlagwort(e): Convection ; Lorenz model ; rotating Rayleigh-Bénard problem ; bifurcations ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A four-mode model of convection in a rotating fluid layer is studied. The model is an extension of the Lorenz model of Rayleigh-Bénard convection, the extra mode accounting for the regeneration of vorticity by rotation. Perturbation theory is applied to show that the Hopf bifurcations from conductive and steady convective solutions can be either supercritical or subcritical. Perturbation theory is also used at large Rayleigh numbersr to predict novel behavior. Supercritical oscillatory convection of finite amplitude is found by numerical integration of the governing equations. The general picture is of a series of oscillatory solutions stable over larger intervals, interspersed by short bursts of chaos.
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  • 97
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    Journal of statistical physics 83 (1996), S. 1199-1210 
    ISSN: 1572-9613
    Schlagwort(e): Weak intermittency ; chaos ; phase transition ; correlation function ; scaling function ; crossover behavior ; critical slowing down
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Piecewise parabolic maps constitute a family of maps in the fully developed chaotic state and depending on a parameter that can be smoothly tuned to a weakly intermittent situation. Approximate analytic expressions are derived for the corresponding correlation functions. These expressions produce power-law decay at intermittency and a crossover from power-law decay to exponential decay below intermittency. It is shown that the scaling functions and the exponent of the power law depend on the kind of the correlations.
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  • 98
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    Journal of statistical physics 86 (1997), S. 1011-1051 
    ISSN: 1572-9613
    Schlagwort(e): Hamiltonian systems ; resonances ; homoclinic bifurcations ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study the dynamics near the intersection of a weaker and a stronger resonance inn-degree-of-freedom, nearly integrable Hamiltonian systems. For a truncated normal form we show the existence of (n−2)-dimensional hyperbolic invariant tori whose whiskers intersect inmultipulse homoclinic orbits with large splitting angles. The homoclinic obits are doubly asymptotic to solutions that “diffuse” across the weak resonance along the strong resonance. We derive a universalhomoclinic tree that describes the bifurcations of these orbits, which are shown to survive in the full normal form. We illustrate our results on a three-degree-of-freedom mechanical system.
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  • 99
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    Foundations of physics 9 (1996), S. 25-41 
    ISSN: 1572-9524
    Schlagwort(e): complexity ; chaos ; symmetry-breaking ; decoherence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract At first sight, an accurate description of the state of the universe appears to require a mind-bogglingly large and perhaps even infinite amount of information, even if we restrict our attention to a small subsystem such as a rabbit. In this paper, it is suggested that most of this information is merely apparent, as seen from our subjective viewpoints, and that the algorithmic information content of the universe as a whole is close to zero. It is argued that if the Schrödinger equation is universally valid, then decoherence together with the standard chaotic behavior of certain non-linear systems will make the universe appear extremely complex to any self-aware subsets that happen to inhabit it now, even if it was in a quite simple state shortly after the big bang. For instance, gravitational instability would amplify the microscopic primordial density fluctuations that are required by the Heisenberg uncertainty principle into quite macroscopic inhomogeneities, forcing the current wavefunction of the universe to contain such Byzantine super-positions as our planet being in many macroscopically different places at once. Since decoherence bars us from experiencing more than one macroscopic reality, we would see seemingly complex constellations of starsetc., even if the initial wavefunction of the universe was perfectly homogeneous and isotropic.
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  • 100
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    International journal of thermophysics 16 (1995), S. 101-110 
    ISSN: 1572-9567
    Schlagwort(e): equation of state ; R 134a ; refrigerants ; simulated annealing ; stepwise regression ; thermodynamic properties
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Refrigerant R134a (1,1.1,2-tetrafuoroethane) is a leading substitute for refrigerant R12. As such, there has been worldwide activity to develop accurate wide-range equations of state for this fluid. In this study. we have developed a new selection algorithm for determining high-accuracy equations of state in the Helmholtz representation. This method combines least-squares regression analysis with simulated annealing optimization. Simulated annealing, unlike stepwise regression, allows for the controlled acceptance of random increases in the objective function. Thus, this procedure produces a computationally efficient selection algorithm which is not susceptible to the function-space local-minima problems present in a purely stepwise regression approach. Two equations are presented in this work and compared against experimental data and other high-accuracy equations of state for R134a. One equation was produced strictly by using stepwise a regression algorithm, while the other was produced using the simulated-annealing selection algorithm. In both cases the temperature dependence of the equations was restricted to have no terms whose exponents were greater than live.
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