Search results for "dynamical system"
showing 10 items of 523 documents
Testing Mode-Coupling Theory for a Supercooled Binary Lennard-Jones Mixture II: Intermediate Scattering Function and Dynamic Susceptibility
1995
We have performed a molecular dynamics computer simulation of a supercooled binary Lennard-Jones system in order to compare the dynamical behavior of this system with the predictions of the idealized version of mode-coupling theory (MCT). By scaling the time $t$ by the temperature dependent $\alpha$-relaxation time $\tau(T)$, we find that in the $\alpha$-relaxation regime $F(q,t)$ and $F_s(q,t)$, the coherent and incoherent intermediate scattering functions, for different temperatures each follows a $q$-dependent master curve as a function of scaled time. We show that during the early part of the $\alpha$-relaxation, which is equivalent to the late part of the $\beta$-relaxation, these mast…
Nonmonotonical crossover of the effective susceptibility exponent
1997
We have numerically determined the behavior of the magnetic susceptibility upon approach of the critical point in two-dimensional spin systems with an interaction range that was varied over nearly two orders of magnitude. The full crossover from classical to Ising-like critical behavior, spanning several decades in the reduced temperature, could be observed. Our results convincingly show that the effective susceptibility exponent gamma_eff changes nonmonotonically from its classical to its Ising value when approaching the critical point in the ordered phase. In the disordered phase the behavior is monotonic. Furthermore the hypothesis that the crossover function is universal is supported.
Exponents of non-linear clustering in scale-free one-dimensional cosmological simulations
2012
One dimensional versions of cosmological N-body simulations have been shown to share many qualitative behaviours of the three dimensional problem. They can resolve a large range of time and length scales, and admit exact numerical integration. We use such models to study how non-linear clustering depends on initial conditions and cosmology. More specifically, we consider a family of models which, like the 3D EdS model, lead for power-law initial conditions to self-similar clustering characterized in the strongly non-linear regime by power-law behaviour of the two point correlation function. We study how the corresponding exponent \gamma depends on the initial conditions, characterized by th…
A dynamical systems study of the inhomogeneous Lambda-CDM model
2010
We consider spherically symmetric inhomogeneous dust models with a positive cosmological constant, $\Lambda$, given by the Lemaitre-Tolman-Bondi metric. These configurations provide a simple but useful generalization of the Lambda-CDM model describing cold dark matter (CDM) and a Lambda term, which seems to fit current cosmological observations. The dynamics of these models can be fully described by scalar evolution equations that can be given in the form of a proper dynamical system associated with a 4-dimensional phase space whose critical points and invariant subspaces are examined and classified. The phase space evolution of various configurations is studied in detail by means of two 2-…
Critical Attractor and Universality in a Renormalization Scheme for Three Frequency Hamiltonian Systems
1998
We study an approximate renormalization-group transformation to analyze the breakup of invariant tori for three degrees of freedom Hamiltonian systems. The scheme is implemented for the spiral mean torus. We find numerically that the critical surface is the stable manifold of a critical nonperiodic attractor. We compute scaling exponents associated with this fixed set, and find that they can be expected to be universal.
Nondegeneracy in the Perturbation Theory of Integrable Dynamical Systems
1990
The most general nondegeneracy condition for the existence of invariant tori in nearly integrable and analytic Hamiltonian systems is formulated.
Nearly-integrable dissipative systems and celestial mechanics
2010
The influence of dissipative effects on classical dynamical models of Celestial Mechanics is of basic importance. We introduce the reader to the subject, giving classical examples found in the literature, like the standard map, the Hénon map, the logistic mapping. In the framework of the dissipative standard map, we investigate the existence of periodic orbits as a function of the parameters. We also provide some techniques to compute the breakdown threshold of quasi-periodic attractors. Next, we review a simple model of Celestial Mechanics, known as the spin-orbit problem which is closely linked to the dissipative standard map. In this context we present the conservative and dissipative KA…
The influence of the solvent's mass on the location of the dividing surface for a model Hamiltonian
2019
The Transition State dividing surface is a key concept, not only for the precise calculation of the rate constant of a reaction, but also for the proper prediction of product ratios. The correct location of this surface is defined by the requirement that reactive trajectories do not recross it. In the case of reactions in solution the solvent plays an important role in the location of the dividing surface. In this paper we show with the aid of a model Hamiltonian that the effective mass of the solvent can dramatically change the location of the dividing surface. Keywords: Dynamical systems, Dividing surface, Reactions in solution, 2019 MSC: 00-01, 99-00
Moment Equations for a Spatially Extended System of Two Competing Species
2005
The dynamics of a spatially extended system of two competing species in the presence of two noise sources is studied. A correlated dichotomous noise acts on the interaction parameter and a multiplicative white noise affects directly the dynamics of the two species. To describe the spatial distribution of the species we use a model based on Lotka-Volterra (LV) equations. By writing them in a mean field form, the corresponding moment equations for the species concentrations are obtained in Gaussian approximation. In this formalism the system dynamics is analyzed for different values of the multiplicative noise intensity. Finally by comparing these results with those obtained by direct simulat…
Quantization as a consequence of the group law
1982
A method of gemetric quantization which solely makes use of the structure of the symmetry group of the dynamical system is proposed; the classical limit is discussed along similar lines. The method is applied to two examples, the free particle and the harmonic oscillator.