Non-Baryonic Dark Matter - Observational Evidence and Detection Methods
L. Bergstrom
TL;DR
This review analyzes how the universe's energy budget is partitioned among baryons, non-baryonic dark matter, and vacuum energy within the standard big bang framework. It argues that inflation drives a flat geometry ( $Ω_{tot} ≈ 1$ ) and that combining SN Ia, CMB, LSS, and gravitational lensing data yields $Ω_M ≈ 0.3–0.4$ and $Ω_\Lambda ≈ 0.6–0.7$. It reviews relic-particle production, including thermal freeze-out of WIMPs with $Ω_χ h^2 ≈ 3×10^{-27} / \langle σ_A v \rangle$ and non-thermal production scenarios, as well as potential axion and massive neutrino contributions. The paper also discusses detection strategies and notes that current experiments are nearing the sensitivity needed to test leading non-baryonic DM candidates, underscoring a ΛCDM-like cosmology with non-baryonic DM.
Abstract
The evidence for the existence of dark matter in the universe is reviewed. A general picture emerges, where both baryonic and non-baryonic dark matter is needed to explain current observations. In particular, a wealth of observational information points to the existence of a non-baryonic component, contributing between around 20 and 40 percent of the critical mass density needed to make the universe geometrically flat on large scales. In addition, an even larger contribution from vacuum energy (or cosmological constant) is indicated by recent observations. To the theoretically favoured particle candidates for non-baryonic dark matter belong axions, supersymmetric particles, and of less importance, massive neutrinos. The theoretical foundation and experimental situation for each of these is reviewed. Direct and indirect methods for detection of supersymmetric dark matter are described in some detail. Present experiments are just reaching the required sensitivity to discover or rule out some of these candidates, and major improvements are planned over the coming years.