Abell 2744: Too much substructure for Lambda CDM?

The massive substructures found in Abell 2744 by Jauzac et al. present a challenge to the cold dark matter paradigm due to their number and proximity to the cluster centre. We use one of the biggest N-body simulations, the Millennium XXL, to investigate the substructure in a large sample of massive dark matter haloes. A range of effects that influence the comparison with the observations is consid...