Orateur
Description
While the standard Lambda-CDM model has been an excellent empirical fit since the discovery of cosmic acceleration, theoretical challenges surrounding the cosmological constant (Lambda) have strongly motivated the exploration of alternative MG and dynamical DE frameworks. Investigating the physical nature of this acceleration requires N-body simulations, preparing for the high-precision data from upcoming Stage-IV surveys, it is strictly required to probe the non-linear growth of cosmic structure. In this paper, we present EFTRAMSES, a comprehensive extension of the ECOSMOG N-body simulation code designed to explore non-linear structure formation in these MG and DE scenarios. We embed the EFTofDE framework into our computational pipeline, utilising the alpha-basis parameterisation to demonstrate the code's capability to directly simulate the EFT framework itself. To validate this new architecture, we additionally map and simulate structure formation within the GCCG model, comparing the resulting non-linear matter power spectra against independent, established baseline code. Our results demonstrate excellent code-to-code agreement, achieving sub-percent precision on linear and quasi-linear scales (k ≤ 1 h/Mpc) and remaining strictly bounded within a 1-2% margin deep into the non-linear regime across multiple cosmic epochs. Crucially, EFTRAMSES successfully captures the highly non-linear Vainshtein screening mechanisms accurately reproducing the ~7% peak enhancement in structure formation at quasi-linear scales before dynamically suppressing the fifth force in high density environments. By consolidating diverse scalar-tensor theories into a single "master" Vainshtein equation, this pipeline provides a robust and versatile computational tool for generating the precise non-linear predictions required for upcoming cosmological surveys.