Matter is classified as Hot Dark Matter (HDM) because the velocities of the particles are moving at relativistic speeds. Because of their speeds, the particles have extremely low masses - about 1 eV. Like CDM, HDM does not interact with the strong and the electromagnetic forces. It does interact with the weak and gravitation forces but extremely weakly. HDM is extremely hard to detect as it rarely interacts with any other matter and move at extremely relativistic speeds - \(0.999 \%\) the speed of light. (7)
Possible HDM candidates would be neutrinos. Discussed in more detail later in this report.