paper

Gravitational softening as a smoothing operation

arXiv:1205.2729 · doi:10.1111/j.1365-2966.2012.21462.x

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.

17 pages, 17 figures. Published in Mon. Not. R. Astron. Soc. 425, 1104-1120 (2012); accepted 2012 June 3. To get a copy with high-resolution figures, download code or data files, or see supplemental plots, visit http://www.ifa.hawaii.edu/~barnes/research/smoothing/

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