Cosmology: small-scale issues

The abundance of dark matter satellites and subhalos, the existence density cusps at the centers of dark matter halos and problems producing disk galaxies in simulations are issues that have raised concerns about viability of the standard cold dark matter (3CDM) scenario for galaxy . This paper reviews these issues and considers the implications for versus various varieties of warm dark matter (WDM). The current evidence to be consistent with standard 3CDM, although improving data may toward a rather tepid version of 3WDM—tepid since the dark matter be very warm without violating observational constraints. (This is a updated and expanded version of my talk at the DM08 meeting Marina Del Rey, arXiv:0902.2506.)