E5 Dark Matter

Topic

Dark matter—which makes up nearly a quarter of the universe's total energy content—is the central figure of this model.

Evidence for the existence of dark matter is manifold and mutually independent: flat rotation curves, where rotational velocity remains constant rather than decreasing at large radii; the dynamics of galaxy clusters; gravitational lensing; and the large-scale structure of the universe itself.

The density profile of these dark matter halos, derived from N-body simulations, drops off much more gradually near the halo's center than at greater distances.

Weakly interacting massive particles (WIMPs)—possessing specific mass and annihilation cross-section values—almost automatically reproduce the dark matter abundance observed today; this coincidence is so striking that it is known as the "WIMP miracle." Axions, meanwhile, represent an alternative candidate motivated by a completely different problem in particle physics. To date, however, no experiment has achieved a direct, conclusive detection of either candidate. Thus, from the dark matter with which this document begins to the as-yet-unrealized detection with which it concludes—encompassing the independent evidence and halo density profiles—dark matter ensures that a quarter of the entire universe remains simultaneously its best-explained and least-observed component.

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