Numerical methods for General Relativistic particles

TL;DR

This paper introduces advanced numerical algorithms for simulating photon and particle trajectories near compact objects like black holes and neutron stars, aiding in understanding relativistic effects and aiding observational comparisons.

Contribution

It presents generalized algorithms capable of simulating ensembles of particles in any spacetime, including external forces, and discusses coupling with GRMHD simulations for astrophysical insights.

Findings

Algorithms successfully simulate photon and particle trajectories in strong gravity.

Coupling with GRMHD enhances understanding of accretion disks and jets.

Tools facilitate comparison with observational data from Event Horizon Telescope.

Abstract

We present recent developments on numerical algorithms for computing photon and particle trajectories in the surrounding of compact objects. Strong gravity around neutron stars or black holes causes relativistic effects on the motion of massive particles and distorts light rays due to gravitational lensing. Efficient numerical methods are required for solving the equations of motion and compute i) the black hole shadow obtained by tracing light rays from the object to a distant observer, and ii) obtain information on the dynamics of the plasma at the microscopic scale. Here, we present generalized algorithms capable of simulating ensembles of photons or massive particles in any spacetime, with the option of including external forces. The coupling of these tools with GRMHD simulations is the key point for obtaining insight on the complex dynamics of accretion disks and jets and for comparing simulations with upcoming observational results from the Event Horizon Telescope.