Are There Problems Associated with the CDM Model?
But there are problems with CDM.
First of all, the particle of choice for CDM is a WIMP - Weakly Interacting Massive Particle, but these non-baryonic- WIMPs are yet to be identified. Computer simulations of the CDM model show the presence of low mass galactic halos, which are yet to be identified.
Cuspy halo and missing dwarf galaxies are two other problems with cold dark matter.
The cuspy halo problem:
CDM proposed the possibility of higher cold dark matter concentration in the center of the galaxy than in other areas. But scientists are yet to find substantial evidence for such cusp or spike in the concentration of dark matter in the center of galaxies. This disagreement between the observed data and the proposal is called the cuspy halo problem.
The missing dwarf galaxy problem:
CDM predicts the presence of a large number of small dwarf galaxies in the vicinity of large galaxies like the Milky Way, but the observational data does not support this. But, in 2007 two scientists, Dr. Josh Simon and Dr. Marla Geha published their study that indicates the number of small dwarf galaxies is larger than expected, thereby increasing the acceptance of CDM. It led to the proposal that these dwarf galaxies are composed of dark matter and have few stars thus making it impossible to detect through direct methods. Even though CDM cold dark matter has a number of problems, it is one of the most accepted models of the Universe.