$\texttt{Hi-COLA}$: Fast, approximate simulations of structure formation in Horndeski gravity

Understand

We introduce $\texttt{Hi-COLA}$, a code designed to run fast, approximate $\textit{N}$-body simulations of non-linear structure formation in reduced Horndeski gravity.

• Given an input Lagrangian, $\texttt{Hi-COLA}$ dynamically constructs the appropriate field equations and consistently solves for the cosmological background, linear growth, and screened fifth force of that theory.
• Hence $\texttt{Hi-COLA}$ is a general, adaptable, and useful tool that allows the mildly non-linear regime of many Horndeski theories to be investigated for the first time, at low computational cost.
• In this work, we first describe the screening approximations and simulation setup of $\texttt{Hi-COLA}$ for theories with Vainshtein screening.