A new Monte Carlo method for dynamical evolution of non-spherical stellar systems

TL;DR

This paper introduces a novel Monte Carlo simulation method for modeling the dynamical evolution of non-spherical stellar systems, combining potential expansion and local velocity diffusion to capture secular shape changes.

Contribution

The paper presents a new Monte Carlo approach that allows for flexible, scalable simulation of non-spherical stellar systems' evolution, bridging existing methods.

Findings

Enables tracking of shape evolution in stellar systems.

Allows independent scaling of two-body relaxation effects.

Potential applications in galaxy and globular cluster dynamics.

Abstract

We have developed a novel Monte Carlo method for simulating the dynamical evolution of stellar systems in arbitrary geometry. The orbits of stars are followed in a smooth potential represented by a basis-set expansion and perturbed after each timestep using local velocity diffusion coefficients from the standard two-body relaxation theory. The potential and diffusion coefficients are updated after an interval of time that is a small fraction of the relaxation time, but may be longer than the dynamical time. Thus our approach is a bridge between the Spitzer's formulation of the Monte Carlo method and the temporally smoothed self-consistent field method. The primary advantages are the ability to follow the secular evolution of shape of the stellar system, and the possibility of scaling the amount of two-body relaxation to the necessary value, unrelated to the actual number of particles in the simulation. Possible future applications of this approach in galaxy dynamics include the problem of consumption of stars by a massive black hole in a non-spherical galactic nucleus, evolution of binary supermassive black holes, and the influence of chaos on the shape of galaxies, while for globular clusters it may be used for studying the influence of rotation.