N-body Galaxy Simulation Dataset for Chaos Analysis

This dataset contains the numerical simulation outputs presented in “The exponential growth of infinitesimal perturbations in the long-term evolution of simulated galaxies” by Asano & Portegies Zwart (arXiv:2604.12053). The simulations investigate the chaotic nature of self-gravitating N-body galaxy models by comparing reference runs and perturbed runs that differ only by an infinitesimal perturbation in the initial conditions.

Each simulation consists of a pair (or ensemble) of runs:

• Reference run: r_xx_0
• Perturbed runs: r_xx_i (i = 1, 2, ...)

The perturbed runs are generated by applying a small displacement to a single particle in the initial condition of the reference run, leading to exponential divergence in phase space.

List of simulations

• r_xx_0 and r_xx_i (i ≥ 1) represent the reference and perturbed runs, respectively.
• Stellar particle data only.
• Data are stored in compressed NumPy binary format (.npz).
• Arrays have shape $T \times N \times 6$, where $T$ and $N$ are the number of snapshots and particles; the last axis corresponds to 6D phase-space coordinates $(x,y,z,v_x,v_y,v_z)$.
• Snapshot interval: $1\, \mathrm{kpc}/ (100 \mathrm{km\, s^{−1}}) \approx 9.78 \, \mathrm{Myr}$.
• Positions and velocities are given in dimensionless N-body units (Hénon 1971).
• Particle ordering is identical between paired runs, enabling direct comparison.

Code examples

https://github.com/tetsuroasano/ChaosTASPZ26