COLD DARK MATTER COSMOLOGY: STATUS AND OPEN QUESTIONS

Cold Dark Matter (CDM) has become the standard modern theory of cosmological structure formation. But despite its many successes, there has been concern about CDM on small scales since the 1994 papers by Flores and Primack and by Moore pointing out the contradiction between the linearly rising rotation curves observed in dwarf galaxies and the 1/r density cusps at the centers of simulated CDM halos. Other CDM issues include the very large number of small satellite halos in simulations, far more than the number of small galaxies observed locally, and possible disagreements between predicted and observed power spectra. The latest data have lessened, although not resolved, many of these concerns. Meanwhile, the main alternatives to CDM that have been considered to solve these problems, self-interacting dark matter (SIDM) and warm dark matter (WDM), have been found to have serious drawbacks.