= Gravitational softening
{title2=$\epsilon$}
<Gravitational softening> regularizes a simulation particle's short-distance <force>, for example by replacing $-Gm/r$ by $-Gm/\sqrt{r^2+\epsilon^2}$. It suppresses artificial close encounters and effectively raises the diffusion cutoff to order $\max(\epsilon,Gm/u^2)$, but alters the resolved <force> below $\epsilon$. Particle number, softening and duration must be chosen together; a point-particle relaxation estimate alone does not specify a simulation's accuracy.
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