EXP: N-body integration using basis function expansions

Understand

We present the N-body simulation techniques in EXP.

• EXP uses empirically-chosen basis functions to expand the potential field of an ensemble of particles.
• Unlike other basis function expansions, the derived basis functions are adapted to an input mass distribution, enabling accurate expansion of highly non-spherical objects, such as galactic discs.
• We measure the force accuracy in three models, one based on a spherical or aspherical halo, one based on an exponential disc, and one based on a bar-based disc model.