N-body Simulations of Large-Scale Structure in the Generalized Cubic Covariant Galileon Model

We present the first N-body simulations of structure formation in the Generalized Cubic Covariant Galileon (GCCG) model. This theory extends the cubic covariant Galileon through power-law kinetic and cubic derivative interactions and admits tracker solutions leading to late-time cosmic acceleration. Previous studies of GCCG have mostly focused on the background, linear perturbations, or semi-analytic nonlinear prescriptions. Here we implement the nonlinear scalar-field equation in the ECOSMOG adaptive-mesh refinement code, allowing us to follow the coupled evolution of matter clustering and Vainshtein screening in the fully nonlinear regime. We quantify the impact of GCCG on the nonlinear matter power spectrum and compare the simulation results with predictions from the halo-model reaction approach. For the parameter choices considered, the GCCG model enhances the matter power spectrum relative to the corresponding QCDM cosmology, with the effect increasing towards low redshift and reaching approximately 7% at z=0 in the transition to the nonlinear regime. At smaller scales, the enhancement decreases as a consequence of Vainshtein screening. We find that the reaction framework captures the qualitative behaviour of the simulations, while residual differences appear on deeply nonlinear scales. We also analyse the abundance of dark matter haloes, finding an enhancement relative to QCDM that becomes more pronounced towards lower redshift and in the high-mass tail. These simulations provide the first nonlinear calibration of structure formation in GCCG and establish the range of validity of efficient semi-analytical predictions for applications to forthcoming large-scale-structure surveys.