FAST: A Fully Asynchronous Split Time-Integrator for Self-Gravitating Fluid

TL;DR

The paper introduces a new asynchronous split time-integrator for self-gravitating fluids that reduces computational time significantly while maintaining accuracy, by splitting the Hamiltonian and using different time-steps for gravitational and other energies.

Contribution

It presents a novel asynchronous integration scheme that efficiently handles self-gravitating fluids with reduced computational cost compared to traditional methods.

Findings

Number of gravitational time-steps reduced by nearly an order of magnitude.

Total simulation time significantly decreased in realistic galaxy merger test.

Simulation accuracy comparable to traditional methods maintained.

Abstract

We describe a new algorithm for the integration of self-gravitating fluid systems using SPH method. We split the Hamiltonian of a self-gravitating fluid system to the gravitational potential and others (kinetic and internal energies) and use different time-steps for their integrations. The time integration is done in the way similar to that used in the mixed variable or multiple stepsize symplectic schemes. We performed three test calculations. One was the spherical collapse and the other was an explosion. We also performed a realistic test, in which the initial model was taken from a simulation of merging galaxies. In all test calculations, we found that the number of time-steps for gravitational interaction were reduced by nearly an order of magnitude when we adopted our integration method. In the case of the realistic test, in which the dark matter potential dominates the total system, the total calculation time was significantly reduced. Simulation results were almost the same with those of simulations with the ordinary individual time-step method. Our new method achieves good performance without sacrificing the accuracy of the time integration.