TreePM
TreePM is a class of algorithms for computing gravitational forces in N-body simulations, combining a Barnes-Hut tree method with a Particle-Mesh (PM) approach. It is widely used in astrophysics and cosmology to simulate the formation of large-scale structure because it balances accuracy and efficiency for systems with very large numbers of particles. The PM component handles long-range forces on a fixed spatial mesh, while the tree component resolves short-range forces within localized regions.
In a typical TreePM scheme, the gravitational force is split into long-range and short-range parts using a
TreePM offers efficient scaling for large simulations, enabling runs with millions to billions of particles. It
Limitations include sensitivity to the chosen split scale and mesh resolution, potential artifacts at the transition