Abstract :
A large gravitational (or classical atomic) N-body simulation typically includes fast binary stars, planet-moon systems, or other tightly bound objects, demanding a small timestep and effectively limiting the time interval over which simulation can take place. While ad-hoc averaging schemes have been used before, these are generally neither symplectic nor reversible, impairing their long time-interval stability properties. In this article, we describe the design of a powerful reversible integrator based on partitioning, averaging, reversible adaptive timestepping, and smooth force decomposition. This method also incorporates a modification of the reversible averaging method of [J. Comput. Phys. 171 (2001) 95] based on an interpolation of the forces acting on the fast variables which is potentially much more efficient than the original method.
