scholarly journals Exotic final states in the $$\varphi ^8$$ multi-kink collisions

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
Vakhid A. Gani ◽  
Aliakbar Moradi Marjaneh ◽  
Kurosh Javidan
Keyword(s):  
Numerical Experiments ◽  
Initial Conditions ◽  
Theoretic Model ◽  
Final States ◽  
Topological Sector ◽  
Resonance Phenomena

AbstractWe study final states in the scattering of kinks and antikinks of the $$\varphi ^8$$ φ 8 field-theoretic model. We use the initial conditions in the form of two, three or four static or moving kinks. In the numerical experiments we observe a number of different processes such as emergence of static and moving oscillons, change of the kink’s topological sector, scattering of an oscillon by a kink, production of kink–antikink pairs in oscillon–oscillon collisions. In antikink–kink collisions for asymmetric kinks, we found resonance phenomena – escape windows.

Spectral analysis of forced turbulence in a non-neutral plasma

2017 ◽  
Vol 83 (3) ◽  
Author(s):  
S. Chen ◽  
G. Maero ◽  
M. Romé
Keyword(s):  
Initial Conditions ◽  
Initial Density ◽  
Final States ◽  
Self Similarity ◽  
Subsequent Formation ◽  
Electron Plasmas ◽  
Particle In Cell ◽  
Fluid Turbulence ◽  
Inviscid Incompressible Fluid ◽  
Forced Turbulence

The paper investigates the dynamics of magnetized non-neutral (electron) plasmas subjected to external electric field perturbations. A two-dimensional (2-D) particle-in-cell code is effectively exploited to model this system with a special attention to the role that non-axisymmetric, multipolar radio frequency (RF) drives applied to the cylindrical (circular) boundary play on the insurgence of azimuthal instabilities and the subsequent formation of coherent structures preventing the relaxation to a fully developed turbulent state, when the RF fields are chosen in the frequency range of the low-order fluid modes themselves. The isomorphism of such system with a 2-D inviscid incompressible fluid offers an insight into the details of forced 2-D fluid turbulence. The choice of different initial density (i.e. fluid vorticity) distributions allows for a selection of conditions where different levels of turbulence and intermittency are expected and a range of final states is achieved. Integral and spectral quantities of interest are computed along the flow using a multiresolution analysis based on a wavelet decomposition of both enstrophy and energy 2-D maps. The analysis of a variety of cases shows that the qualitative features of turbulent relaxation are similar in conditions of both free and forced evolution; at the same time, fine details of the flow beyond the self-similarity turbulence properties are highlighted in particular in the formation of structures and their timing, where the influence of the initial conditions and the effect of the external forcing can be distinguished.

scholarly journals Rotational Behavior of Cometary-type Bodies

1992 ◽  
Vol 152 ◽  
pp. 291-296
Author(s):  
Eric Bois ◽  
Pascal Oberti ◽  
Claude Froeschlé
Keyword(s):  
Qualitative Study ◽  
Rotational Motion ◽  
Numerical Experiments ◽  
Initial Conditions ◽  
Close Approach ◽  
Rotational Behavior ◽  
Comet Nucleus ◽  
Gravitational Perturbation ◽  
The Sun ◽  
Sensitivity To Initial Conditions

The present paper deals with a general dynamical qualitative study of the rotational motion for cometary-type bodies submitted to gravitational torques. Numerical experiments of the evolution of comet nucleus attitude have been then performed, including the Sun and Jupiter's disturbing torques in the model. Results show small effects of the solar gravitational perturbation for Halley-type orbits. Only a very close-approach with Jupiter induces notable effects. The latter configuration presents some interesting sensitivity to initial conditions.

scholarly journals PEDESTRIAN FLOW MODELS WITH SLOWDOWN INTERACTIONS

2013 ◽  
Vol 24 (02) ◽  
pp. 249-275 ◽  
Author(s):  
ALINA CHERTOCK ◽  
ALEXANDER KURGANOV ◽  
ANTHONY POLIZZI ◽  
ILYA TIMOFEYEV
Keyword(s):  
Numerical Experiments ◽  
Initial Conditions ◽  
Coupled System ◽  
Coarse Grained ◽  
Order System ◽  
Stochastic Cellular Automata ◽  
Cellular Automata Model ◽  
Flow Models ◽  
Pedestrian Traffic ◽  
Microscopic Stochastic Model

In this paper, we introduce and study one-dimensional models for the behavior of pedestrians in a narrow street or corridor. We begin at the microscopic level by formulating a stochastic cellular automata model with explicit rules for pedestrians moving in two opposite directions. Coarse-grained mesoscopic and macroscopic analogs are derived leading to the coupled system of PDEs for the density of the pedestrian traffic. The obtained first-order system of conservation laws is only conditionally hyperbolic. We also derive higher-order nonlinear diffusive corrections resulting in a parabolic macroscopic PDE model. Numerical experiments comparing and contrasting the behavior of the microscopic stochastic model and the resulting coarse-grained PDEs for various parameter settings and initial conditions are performed. These numerical experiments demonstrate that the nonlinear diffusion is essential for reproducing the behavior of the stochastic system in the nonhyperbolic regime.

Effect of initial conditions on electron–plasma turbulence: a multiresolution analysis

2015 ◽  
Vol 81 (5) ◽  
Author(s):  
S. Chen ◽  
G. Maero ◽  
M. Romé
Keyword(s):  
Multiresolution Analysis ◽  
Initial Conditions ◽  
Initial Density ◽  
Electron Plasma ◽  
Plasma Turbulence ◽  
Considerable Effect ◽  
Density Fluctuations ◽  
Final States ◽  
Particle In Cell ◽  
Similar Growth

The transverse dynamics of a pure electron plasma confined in a Penning–Malmberg trap is investigated, taking advantage of two-dimensional particle-in-cell numerical simulations. The evolution of the electron plasma turbulence is studied by means of a wavelet-based multiresolution analysis. In particular, a modified recursive denoising algorithm is developed to separate coherent and incoherent (not necessarily homogeneous) components of the flow. A set of simulations have been carried out changing systematically the radii of an initial annular density distribution of the electrons. The results of the multiresolution analysis indicate that the initial density configuration may have a considerable effect on the evolution of turbulence. Even very small initial density fluctuations can lead to quite different final states, especially in the presence of multiple active diocotron modes characterized by similar growth rates.

scholarly journals Exit basins for the Sitnikov problem with variable mass

2020 ◽  
Vol 25 (1) ◽  
pp. 150-157
Author(s):  
Fredy Leonardo Dubeibe ◽  
Guillermo Alfonso Gonzalez ◽  
Edgar Acosta
Keyword(s):  
Test Particle ◽  
Initial Conditions ◽  
Numerical Study ◽  
Variable Mass ◽  
Final States ◽  
Sitnikov Problem ◽  
Final State ◽  
Oscillatory State

In the present paper, we perform a numerical study of the Sitnikov problem aiming to characterize the orbits of a variable mass particle (e.g., comet, rocket, asteroid or spacecraft) and determine the uncertainty in the prediction of the final state of the test particle. The classification of final states was done through the well-known exit basins, while the determination of the uncertainty was calculated using a new tool named Basin entropy. It is found that for small values of the initial mass of the test particle, the number of initial conditions leading to bounded orbits gets increased, thus reducing the uncertainty in the final states. The same behavior in uncertainty is observed for increasing values of the exponent in Jeans law for the variation of the mass. Our results allow us to conclude that: i) an accelerated fuel consumption in the initial stages of stabilization of a satellite can keep the object in an oscillatory state around the primaries and ii) if the mass of the satellite is less than one hundredth of the mass of each primary, it is possible to predict with a very high certainty the final state of the satellite, regardless of the accuracy in the initial conditions of the system.

scholarly journals Numerical Experiments on the Motion of the Outer Planets

1992 ◽  
Vol 152 ◽  
pp. 25-32 ◽  
Author(s):  
Gerald D. Quinlan
Keyword(s):  
Lyapunov Exponent ◽  
Solar System ◽  
Probability Distribution ◽  
Numerical Experiments ◽  
Initial Conditions ◽  
Major Axis ◽  
Solar Systems ◽  
Outer Planets ◽  
System A ◽  
Real Value

We have integrated the motion of the four Jovian planets on Myr timescales in fictitious solar systems in which the orbits differ from those of the real solar system. A change of ≲1% in the major axis of any one of the planets from its real value can lead to chaotic motion with a Lyapunov exponent larger than 10-5 yr−1. A survey of fifty solar systems with initial conditions chosen at random from a reasonable probability distribution shows the majority of them to be chaotic.

scholarly journals Kinematics of mass-loss from the outer Lagrange point L2

2019 ◽  
Vol 489 (1) ◽  
pp. 891-899 ◽  
Author(s):  
Dominika Hubová ◽  
Ondřej Pejcha
Keyword(s):  
Mass Loss ◽  
Binary Stars ◽  
Initial Conditions ◽  
Initial Position ◽  
Final States ◽  
Lagrange Point ◽  
Particle Trajectories ◽  
Hydrodynamic Simulations ◽  
Common Envelope ◽  
Tidal Torques

ABSTRACT We investigate kinematics of mass-loss from the vicinity of the second Lagrange point L2 with applications to merging binary stars, common envelope evolution, and the associated transient brightenings. For ballistic particle trajectories, we characterize initial velocities and positional offsets from L2 that lead to unbound outflow, fall back followed by a formation of a decretion disc, collision with the binary surface, or a hydrodynamic shock close to the binary, where some particle trajectories loop and self-intersect. The latter two final states occur only when the trajectories are initiated with offset from L2 or with velocity vector different from corotation with the binary. We find that competition between the time-dependent and steeply radially decreasing tidal torques from the binary, Coriolis force, and initial conditions lead to a non-trivial distribution of outcomes in the vicinity of L2. Specifically, even for initial velocities slower than corotation, we find that a set of initial position offsets leads to unbound outflows. Our results will aid in the interpretation of the morphology of mass-loss streams in hydrodynamic simulations.

scholarly journals Properties of self-gravitating quasi-stationary states

2020 ◽  
Vol 643 ◽  
pp. A118
Author(s):  
Francesco Sylos Labini ◽  
Roberto Capuzzo-Dolcetta
Keyword(s):  
Density Profile ◽  
Numerical Experiments ◽  
Energy Exchange ◽  
Initial Conditions ◽  
Initial Density ◽  
Density Fluctuations ◽  
Quasi Equilibrium ◽  
Stationary States ◽  
Top Down ◽  
Bottom Up

Initially far out-of-equilibrium, self-gravitating systems form quasi-stationary states (QSS) through a collisionless relaxation dynamics. These may arise from a bottom-up aggregation of structures or in a top-down frame; their quasi-equilibrium properties are well described by the Jeans equation and are not universal. These QSS depend on initial conditions. To understand the origin of such dependence, we present the results of numerical experiments of initially cold and spherical systems characterized by various choices of the spectrum of initial density fluctuations. The amplitude of such fluctuations determines whether the system relaxes in a top-down or bottom-up manner. We find that statistical properties of the resulting QSS mainly depend upon the amount of energy exchanged during the formation process. In particular, in the violent top-down collapses the energy exchange is large and the QSS show an inner core with an almost flat density profile and a quasi Maxwell-Boltzmann (isotropic) velocity distribution, while their outer regions display a density profile ρ(r) ∝ r−α (α >  0) with radially elongated orbits. We show analytically that α = 4, in agreement with numerical experiments. In the less violent bottom-up dynamics, the energy exchange is much smaller, the orbits are less elongated, and 0 < α(r) ≤ 4, where the density profile is well fitted by the Navarro-Frenk-White behavior. Such a dynamical evolution is shown by both nonuniform spherical isolated systems and by halos extracted from cosmological simulations. We consider the relation of these results with the core-cusp problem and conclude that this can be solved naturally if galaxies form through a monolithic collapse.

scholarly journals Climate noise effect on uncertainty of hydrological extremes: numerical experiments with hydrological and climate models

2015 ◽  
Vol 369 ◽  
pp. 49-53 ◽  
Author(s):  
A. N. Gelfan ◽  
V. A. Semenov ◽  
Yu. G. Motovilov
Keyword(s):  
Numerical Experiments ◽  
Climate Models ◽  
Hydrological Model ◽  
Climate Model ◽  
Initial Conditions ◽  
Hydrological Regime ◽  
Internal Variability ◽  
Climate Impact ◽  
Noise Effect ◽  
Climate Noise

Abstract. An approach has been proposed to analyze the simulated hydrological extreme uncertainty related to the internal variability of the atmosphere ("climate noise"), which is inherent to the climate system and considered as the lowest level of uncertainty achievable in climate impact studies. To assess the climate noise effect, numerical experiments were made with climate model ECHAM5 and hydrological model ECOMAG. The case study was carried out to Northern Dvina River basin (catchment area is 360 000 km2), whose hydrological regime is characterised by extreme freshets during spring-summer snowmelt period. The climate noise was represented by ensemble ECHAM5 simulations (45 ensemble members) with identical historical boundary forcing and varying initial conditions. An ensemble of the ECHAM5-outputs for the period of 1979–2012 was used (after bias correction post-processing) as the hydrological model inputs, and the corresponding ensemble of 45 multi-year hydrographs was simulated. From this ensemble, we derived flood statistic uncertainty caused by the internal variability of the atmosphere.

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