Journal Article

Gravitational softening as a smoothing operation

Joshua E. Barnes

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 425, issue 2, pages 1104-1120
Published in print September 2012 | ISSN: 0035-8711
Published online September 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21462.x
Gravitational softening as a smoothing operation

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Abstract

In self-consistent N-body simulations of collisionless systems, gravitational interactions are modified on small scales to remove singularities and simplify the task of numerically integrating the equations of motion. This ‘gravitational softening’ is sometimes presented as an ad hoc departure from Newtonian gravity. However, softening can also be described as a smoothing operation applied to the mass distribution; the gravitational potential and the smoothed density obey Poisson's equation precisely. While ‘softening’ and ‘smoothing’ are mathematically equivalent descriptions, the latter has some advantages. For example, the smoothing description suggests a way to set up N-body initial conditions in almost perfect dynamical equilibrium.

Keywords: methods: numerical; galaxies: kinematics and dynamics

Journal Article.  9118 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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