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The statistical properties of the $E \times B$ flux in different types of plasma turbulence simulations are investigated using probability density distribution functions (PDF). The physics included in the models ranges from two dimensional…

Plasma Physics · Physics 2009-11-10 Volker Naulin , Odd Erik Garcia , Anders Henry Nielsen , Jens Juul Rasmussen

We construct the general spherically symmetric and self-similar solution of the Einstein-Vlasov system (collisionless matter coupled to general relativity) with massless particles, under certain regularity conditions. Such solutions have a…

General Relativity and Quantum Cosmology · Physics 2009-11-07 Jose M. Martin-Garcia , Carsten Gundlach

The rarefied flow and multi-scale flow are crucial for the aerodynamic design of spacecraft, ultra-low orbital vehicles and plumes. By introducing a discrete velocity space, the Boltzmann method, such as the discrete velocity method and…

Fluid Dynamics · Physics 2025-04-07 Jianfeng Chen , Sha Liu , Rui Zhang , Chengwen Zhong , Yanguang Yang , Congshan Zhuo

Dynamical symmetries of the collisionless Boltzmann transport equation, or Vlasov equation, but under the influence of an external driving force, are derived from non-standard representations of the $2D$ conformal algebra. In the case…

Mathematical Physics · Physics 2015-09-08 Stoimen Stoimenov , Malte Henkel

The relevance of the vortex-gas model to the large scale dynamics of temporally evolving turbulent free shear layers in an inviscid incompressible fluid has recently been established by extensive numerical simulations (Suryanarayanan et al,…

Fluid Dynamics · Physics 2015-09-04 Saikishan Suryanarayanan , Roddam Narasimha

In this paper we extend Chandrasekhar and von Neumann's analysis of the statistics of the gravitational field to systems in which particles (e.g. stars, galaxies) are not homogeneously distributed. We derive a distribution function…

Astrophysics · Physics 2007-05-23 A. Del Popolo , M. Gambera , x

In this paper, we develop the method of analyzing the velocity field of cosmic matter with a multiresolution decomposition. This is necessary in calculating the redshift distortion of power spectrum in the discrete wavelet transform (DWT)…

Astrophysics · Physics 2009-11-06 Xiao-Hu Yang , Long-Long Feng , Yao-Quan Chu , Li-Zhi Fang

It is presented the general properties of N-dimensional multi-component or many-particle systems exhibiting self-similar hierarchical structure. Assuming there exists an optimal coarse-graining scale at which the quality and diversity of…

Adaptation and Self-Organizing Systems · Physics 2014-04-22 Marcos E. Gaudiano

We study analytically the development of gravitational instability in an expanding shell having finite thickness. We consider three models for the radial density profile of the shell: (i) an analytic uniform-density model, (ii) a…

Astrophysics of Galaxies · Physics 2015-05-19 Richard Wunsch , James E. Dale , Jan Palous , Anthony P. Whitworth

The present work is devoted to the evolution of random solutions of the unforced Burgers and KPZ equations in d-dimensions in the limit of vanishing viscosity. We consider a cellular model and as initial condition assign a value for the…

chao-dyn · Physics 2009-10-31 S. N. Gurbatov

Systems of self-gravitating fermions constitute a topic of great interest in astrophysics, due to the wide field of applications. In this paper, we consider the gravitational equilibrium of spherically symmetric Newtonian models of…

Cosmology and Nongalactic Astrophysics · Physics 2014-07-01 Marco Merafina , Giuseppe Alberti

Assemblies of anisotropic particles commonly appear in studies of active many-body systems. However, in two dimensions, the geometric ramifications of the finite density of such objects are not entirely understood. To fully characterize…

Biological Physics · Physics 2019-05-29 Jakov Lovrić , Sara Kaliman , Wolfram Barfuß , Gerd E. Schröder-Turk , Ana-Sunčana Smith

A steady-state distribution is obtained that approximately yields the observed plasma density profile of the inner Van Allen radiation belt. The model assumes a collisionless, magnetized plasma with zero electric field present. The inner…

Plasma Physics · Physics 2023-10-13 Snehanshu Maiti , Harishankar Ramachandran

We study the dynamics of a twisted tilted disc under the influence of an external radiation field. Assuming the effect of absorption and reemission/scattering is that a pressure is applied to the disc surface where the local optical depth…

Astrophysics · Physics 2009-11-13 P. B. Ivanov , J. C. B. Papaloizou

We study a two-dimensional gas of inelastic rough spheres, driven on the rotational degrees of freedom. Numerical simulations are compared to mean-field (MF) predictions with surprisingly good agreement for strong coupling of rotational and…

Statistical Mechanics · Physics 2007-05-23 R. Cafiero , S. Luding , H. J. Herrmann

Coherent structures created through turbulent cascades play a key role in energy dissipation and particle acceleration. In this work, we investigate both current and vorticity sheets in 3D particle-in-cell simulations of decaying…

Plasma Physics · Physics 2025-10-13 Zachary Davis , Luca Comisso , Colby Haggerty , Joonas Nättilä

The self-similar equilibrium models of self-gravitating, rotating, isothermal systems are investigated analytically. In these models the rotation velocity is constant and the density varies as $\frac{f(\theta, \phi)}{r^2}$, where $r$ and…

Astrophysics · Physics 2009-11-06 Mohsen Shadmehri , Jamshid Ghanbari

The long-time behavior of the velocity autocorrelation function (VACF) is investigated by the molecular dynamics simulation of a two-dimensional system which has both a many-body interaction and a random potential. With strengthening the…

Statistical Mechanics · Physics 2009-11-13 Tatsuro Yuge , Akira Shimizu

We study a pressureless Euler system with a nonlinear density-dependent alignment term, originating in the Cucker-Smale swarming models. The alignment term is dissipative in the sense that it tends to equilibrate the velocities. Its density…

Analysis of PDEs · Mathematics 2017-11-22 Tam Do , Alexander Kiselev , Lenya Ryzhik , Changhui Tan

Diffusivity is a key quantity in describing velocity fluctuations in granular materials. These fluctuations are the basis of many thermodynamic and hydrodynamic models which aim to provide a statistical description of granular systems. We…

Soft Condensed Matter · Physics 2009-11-10 Brian Utter , R. P. Behringer