Description
The large-scale structure of the Universe is one of the most promising probes of the nature of gravity. In this talk, we focus on halos and voids, and study their evolution and abundance in Horndeski and DHOST theories. Using the Effective Field Theory (EFT) of dark energy framework, we investigate the impact of individual EFT parameters on the formation and abundance of these structures. We further derive constraints on the EFT parameters from halo formation, based on the requirement that real solutions for scalar field fluctuations exist at all times.