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We introduce a fast Fourier spectral method for the multi-species Boltzmann collision operator. The method retains the riveting properties of the single-species fast spectral method (Gamba et al. SIAM J. Sci. Comput., 39 pp. B658--B674…

Computational Physics · Physics 2019-05-07 Shashank Jaiswal , Alina A. Alexeenko , Jingwei Hu

We consider the nonlinear boundary layers of the Boltzmann equation in a three-dimensional half-space by perturbing around a Maxwellian, under the assumption that the Mach number of the Maxwellian satisfies ${\cal M}_{\infty} < -1$. In…

Analysis of PDEs · Mathematics 2020-09-17 Shota Sakamoto , Masahiro Suzuki , Katherine Zhiyuan Zhang

We present a numerical algorithm for evaluating the Boltzmann collision operator with $O(N^2)$ operations based on high order discontinuous Galerkin discretizations in the velocity variable. To formulate the approach, Galerkin projection of…

Numerical Analysis · Mathematics 2018-01-19 Alexander Alekseenko , Jeffrey Limbacher

Using the numerical solution of the nonlinear Schroedinger equation and a variational method it is shown that (3+1)-dimensional spatiotemporal optical solitons can be stabilized by a rapidly oscillating dispersion coefficient in a Kerr…

Pattern Formation and Solitons · Physics 2009-11-10 Sadhan K. Adhikari

In this article, we extend the result of Boltzmann on characterisation of collision invariants from the case of hard disks to a class of two-dimensional compact, strictly-convex particles.

Mathematical Physics · Physics 2015-07-29 Laure Saint-Raymond , Mark Wilkinson

We propose a numerical method to compute the inertial modes of a container with near-spherical geometry based on the fully spectral discretisation of the angular and radial directions using spherical harmonics and Gegenbauer polynomial…

Fluid Dynamics · Physics 2019-04-11 J. Rekier , A. Trinh , S. A. Triana , V. Dehant

The article provides an analytical solution of the Navier-Stokes equations for the case of the steady flow of an incompressible fluid between two uniformly co-rotating disks. The solution is derived from the asymptotical evolution of…

Fluid Dynamics · Physics 2007-05-23 Milan Batista

We present a numerical method for computing the pure-point spectrum associated with the linear stability of multi-dimensional travelling fronts to parabolic nonlinear systems. Our method is based on the Evans function shooting approach.…

Dynamical Systems · Mathematics 2009-03-17 Veerle Ledoux , Simon J. A. Malham , Jitse Niesen , Vera Thümmler

We prove general nonlinear stability and existence theorems for rotating star solutions which are axi-symmetric steady-state solutions of the compressible isentropic Euler-Poisson equations in 3 spatial dimensions. We apply our results to…

General Relativity and Quantum Cosmology · Physics 2014-08-04 Tao Luo , Joel Smoller

We introduce four basic two-dimensional (2D) plaquette configurations with onsite cubic nonlinearities, which may be used as building blocks for 2D PT -symmetric lattices. For each configuration, we develop a dynamical model and examine its…

Quantum Physics · Physics 2012-10-24 Kai Li , P. G. Kevrekidis , Boris A. Malomed , Uwe Guenther

We investigate the three-dimensional structure of the pulsar magnetosphere through time-dependent numerical simulations of a magnetic dipole that is set in rotation. We developed our own Eulerian finite difference time domain numerical…

Astrophysics · Physics 2009-11-13 Constantinos Kalapotharakos , Ioannis Contopoulos

We present a formulation of cosmological perturbation theory where the Boltzmann hierarchies that evolve the neutrino phase-space distributions are replaced by integrals that can be evaluated easily with fast Fourier transforms. The…

Cosmology and Nongalactic Astrophysics · Physics 2022-12-14 Lingyuan Ji , Marc Kamionkowski , Jose Luis Bernal

We study the orbital stability and instability of single-spike bound states of semiclassical nonlinear Schrodinger (NLS) equations with critical exponent, linear and nonlinear optical lattices (OLs). These equations may model…

Analysis of PDEs · Mathematics 2010-06-25 Tai-Chia Lin , Juncheng Wei , Wei Yao

We present numerical studies of the properties of the stellar velocity distribution in galactic disks which have developed a saturated, two-armed spiral structure. In previous papers we used the Boltzmann moment equations (BME) up to second…

Astrophysics · Physics 2016-01-27 Christian Theis , Eduard Vorobyov

This study aims to provide an analytical scheme for computing equilibrium configurations of relativistic stars by solving the Tolman-Oppenheimer-Volkoff equations directly in isotropic polar coordinates, as opposed to the commonly applied…

General Relativity and Quantum Cosmology · Physics 2024-06-12 Dániel Barta

The objective of the work summarised here has been to exploit and extend ideas from plasma physics and accelerator dynamics to formulate a unified description of collisionless relaxation that views violent relaxation, Landau damping, and…

Astrophysics · Physics 2007-05-23 Henry E. Kandrup

The high-order hybridizable discontinuous Galerkin (HDG) method combining with an implicit iterative scheme is used to find the steady-state solution of the Boltzmann equation with full collision integral on two-dimensional triangular…

Fluid Dynamics · Physics 2020-02-19 Wei Su , Peng Wang , Yonghao Zhang , Lei Wu

Spectral methods are well suited for solving hydrodynamic problems in which the self-gravity of the flow needs to be considered. Because Poisson's equation is linear, the numerical solution for the gravitational potential for each…

Astrophysics · Physics 2008-11-26 Chi-kwan Chan , Dimitrios Psaltis , Feryal Ozel

It is well known that the linear stability of solutions of partial differential equations which are integrable can be very efficiently investigated by means of spectral methods. We present here a direct construction of the eigenmodes of the…

Exactly Solvable and Integrable Systems · Physics 2018-06-18 Antonio Degasperis , Sara Lombardo , Matteo Sommacal

We present a numerical solution of the quantum Lenard-Balescu equation using a spectral method, namely an expansion in Laguerre polynomials. This method exactly conserves both particles and energy and facilitates the integration over the…

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