Dark matter composition Theory

CDM

HDM

If the Universe cmopostiion is primarly made of hot dark matter, the very high speed of the particles would initially prevent the formation of a structure smaller than the supercluster of galaxies dividing up in galaxy cluster then in galaxies, then in smaller structures.

The best candidate to constitute the hot dark matter is the neutrino.

On the other hand, if the cold dark matter is the main component of the Universe, the particles will go on a smaller distance and thus will erase the density's fluctuations on extents smaller than in the case of hot dark matter. The ordinary matter would then gather to form galaxies (starting from gas clouds and smaller structures), which themselves will gather in cluster, then supercluster

The candidates for cold dark matter are WIMP and MACHO.