Warm dark matter

Definition

Warm dark matter (WDM) is a theoretical form of dark matter that has a mass and thermal velocity between that of cold dark matter and hot dark matter, allowing it to affect the formation of structures in the universe differently than its counterparts. Its properties suggest it could explain certain cosmic phenomena, such as the formation of small-scale structures in the universe while still aligning with large-scale observations.

5 Must Know Facts For Your Next Test

1. Warm dark matter particles are predicted to have masses on the order of a few keV (kilo-electronvolts), bridging the gap between cold and hot dark matter.
2. The presence of warm dark matter can lead to different predictions about the abundance and distribution of small galaxies in the universe compared to cold dark matter models.
3. Observations from galaxy formation and cosmic microwave background radiation provide indirect evidence supporting warm dark matter scenarios.
4. Warm dark matter models can resolve some issues in cosmology, such as the 'missing satellite problem,' where there seem to be fewer small galaxies than expected around larger ones.
5. Current experiments and detection methods focus on identifying signatures of warm dark matter through its potential interactions with normal matter or through indirect detection techniques.

Review Questions

• How does warm dark matter differ from cold and hot dark matter in terms of particle characteristics and their implications for structure formation?
  • Warm dark matter has a mass and thermal velocity that places it between cold and hot dark matter. This means it moves faster than cold dark matter but slower than hot dark matter. As a result, warm dark matter can facilitate the formation of small-scale structures more effectively than hot dark matter while avoiding some issues associated with cold dark matter, such as excessive numbers of small galaxies. Understanding these differences is crucial for explaining various cosmic phenomena.
• Discuss how warm dark matter might resolve discrepancies in observational cosmology, such as the missing satellite problem.
  • The missing satellite problem refers to the discrepancy between predictions made by cold dark matter models about the number of small galaxies around larger ones and actual observations showing fewer satellites. Warm dark matter's unique properties allow it to suppress the formation of too many small galaxies due to its higher velocity, which aligns better with what we observe. This adjustment helps bridge the gap between theoretical predictions and observational data in cosmology.
• Evaluate the potential detection methods for warm dark matter and their implications for our understanding of cosmic structure.
  • Potential detection methods for warm dark matter include direct detection experiments looking for interactions with normal matter and indirect detection that seeks products from warm dark matter annihilations or decays. These methods are crucial because they could provide empirical evidence supporting or refuting warm dark matter theories. A successful detection would not only enhance our understanding of dark matter itself but also reshape our views on cosmic structure formation, leading to new insights about galaxy evolution and distribution.

Related terms

Cold Dark Matter: A type of dark matter that moves slowly compared to the speed of light, leading to the formation of large-scale structures in the universe, such as galaxies and galaxy clusters.

Hot Dark Matter: Dark matter composed of very light particles that travel at relativistic speeds, which can inhibit the formation of small-scale structures due to their high velocity.

Weakly Interacting Massive Particles (WIMPs): A class of particle candidates for dark matter that interact through weak nuclear force, which could include cold or warm dark matter types.