Active Galactic Nuclei (AGN) play a role in cosmology as both component and probe.
They are used to contrain cosmological parameters, to characterize the intergalactic medium, and as a .
AGN interact with their host galaxies, influencing its evolution through a process called AGN feedback.
Modeling AGN feedback presents significant challenges, but has improved upon the \LCDM model as tested by the Millenium Simulation. \cite{2005Natur.435..629S}
The Millenium Run and its following iterations are N-body simulations that predict the evolution of the matter in the universe. It is considered a (successful) test of the \LCDM cosmology.