gevolution: a cosmological N-body code based on General Relativity

TL;DR

gevolution is a new cosmological N-body simulation code based on General Relativity, capable of modeling large scale structures with relativistic effects, including massive neutrinos and potential modifications to gravity.

Contribution

it introduces a relativistic N-body code that calculates all metric degrees of freedom and can incorporate various dark energy or modified gravity models.

Findings

validated against Schwarzschild solution

reproduces Newtonian limit with Gadget-2 and RAMSES

simulated large scale structure with massive neutrinos

Abstract

We present a new N-body code, gevolution, for the evolution of large scale structure in the Universe. Our code is based on a weak field expansion of General Relativity and calculates all six metric degrees of freedom in Poisson gauge. N-body particles are evolved by solving the geodesic equation which we write in terms of a canonical momentum such that it remains valid also for relativistic particles. We validate the code by considering the Schwarzschild solution and, in the Newtonian limit, by comparing with the Newtonian N-body codes Gadget-2 and RAMSES. We then proceed with a simulation of large scale structure in a Universe with massive neutrinos where we study the gravitational slip induced by the neutrino shear stress. The code can be extended to include different kinds of dark energy or modified gravity models and going beyond the usually adopted quasi-static approximation. Our code is publicly available.