Cold dark matter is nonrelativistic early enough that its primordial free-streaming length is small compared with the cosmological structures of interest.
Cold dark matter (CDM) is a theoretical form of matter that makes up a significant portion of the total mass-energy content of the universe. It is a critical component in the standard model of cosmology, particularly in the context of the Big Bang theory and structure formation. Here are some key points about cold dark matter: 1. **Nature**: CDM is "cold" in the sense that it moves slowly compared to the speed of light and has low thermal velocities.
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