Unconvergence of Very Large Scale GI Simulations

TL;DR

This paper investigates the reliability of giant impact simulations in planetary science, revealing that results do not converge with increasing resolution but instead oscillate, raising questions about their validity.

Contribution

It demonstrates that high-resolution GI simulations exhibit non-convergent, oscillatory results, challenging previous assumptions about their reliability.

Findings

Results do not converge with increasing particle number.

Simulation outcomes show oscillatory behavior.

Reliability of GI simulation results is questionable.

Abstract

The giant impact (GI) is one of the most important hypotheses both in planetary science and geoscience, since it is related to the origin of the Moon and also the initial condition of the Earth. A number of numerical simulations have been done using the smoothed particle hydrodynamics (SPH) method. However, GI hypothesis is currently in a crisis. The "canonical" GI scenario failed to explain the identical isotope ratio between the Earth and the Moon. On the other hand, little has been known about the reliability of the result of GI simulations. In this paper, we discuss the effect of the resolution on the results of the GI simulations by varying the number of particles from $3 \times10^3$ to $10^8$. We found that the results does not converge, but shows oscillatory behaviour. We discuss the origin of this oscillatory behaviour.