Warm dark matter has a primordial collisionless free streaming length large enough to suppress the formation of low-mass haloes, while remaining nonrelativistic early enough to cluster on galactic and larger scales.
Warm dark matter (WDM) is a theoretical form of dark matter that falls in energy and mass characteristics between cold dark matter (CDM) and hot dark matter (HDM). The primary distinctions among these categories relate to the speed of the particles and their thermal properties during the early universe.
New to topics? Read the docs here!