Hi! Just reposting an infodump I made for r/cosmology on reddit...

Hi! Just reposting an infodump I made for r/cosmology on reddit in case someone else is interested.
“Although this simulation isn’t new, it’s over a year old. I’ll just info dump about simulations if you don’t mind.
So the simulation itself is worth mentioning. The code used is called AREPO, and it’s ridiculously clever. Broadly, simulation codes work in one of two ways; on a grid, or with particles. Grid simulations split their simulation box up into tiny cubes (cells) that each have associated with them numbers for a temperature, energy, density, amount of hydrogen… etc. At each time-step in the simulation, physics equations (and approximations to them in some cases) are applied to the cubes and their neighbours and the numbers are updated to show e.g. gas moving from one cell into another.
Particle simulations do something different a bit different. Particles are spread out in the box, and particles are assigned a mass. The particles then move in the box under the influence of gravity, so the particles gravitate towards the densest point, giving automatic higher resolution in the denser areas. The resulting particle pattern is smoothed out to calculate the density and other values.
AREPO combines ...