Hot dark matter
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Hot dark matter is a form of dark matter, which consists of particles that travel with relativistic velocities. The best candidate for hot dark matter is the neutrino. Neutrinos have very small mass, and do not partake in two of the four fundamental forces, the electromagnetic interaction, and strong interaction. They do interact with the weak nuclear force, and gravity, and are extremely difficult to detect. A few projects, such as the Super-Kamiokande neutrino observatory, in Gifu, Japan are currently studying these neutrinos.
Dark matter is matter that cannot be detected by electromagnetic radiation. Hence the dark. It is postulated to exist to explain how clusters and superclusters of galaxies formed after the big bang. Data from galaxy rotation curves indicate that around 90% of the mass of a galaxy cannot be seen. It can only be detected by its gravitational effect. In addition to hot dark matter, there are several other types of dark matter postulated to exist: baryonic dark matter and cold dark matter.
Hot dark matter cannot explain how individual galaxies formed from the big bang. The microwave background radiation as measured by the COBE satellite is very smooth and fast moving particles cannot clump together on this small scale from such as smooth initial clumping. To explain small scale structure in the Universe it is necessary to invoke cold dark matter. Hot dark matter therefore is nowadays always discussed as part of a mixed dark matter theory.
External link
- Hot dark matter by Berkeley (http://astron.berkeley.edu/~mwhite/darkmatter/hdm.html)
- Dark Matter (http://csep10.phys.utk.edu/astr162/lect/cosmology/darkmatter.html)pl:Gorąca ciemna materia