The enigma of the dark matter

Abstract

One of the great scientific enigmas still unsolved, the existence of dark matter, is reviewed. Simple gravitational arguments imply that most of the mass in the Universe, at least 90%, is some (unknown) non-luminous matter. Some particle candidates for dark matter are discussed with particular emphasis on the neutralino, a particle predicted by the supersymmetric extension of the Standard Model of particle physics. Experiments searching for these relic particles, carried out by many groups around the world, are also discussed. These experiments are becoming more sensitive every year and in fact one of the collaborations claims that the first direct evidence for dark matter has already been observed.

Singlet fermionic dark matter

“…There are several experiments to detect the WIMP directly through the elastic scattering of the WIMP on the target nuclei [23,24]. The effective Lagrangian describing the elastic scattering of the WIMP and a nucleon is given by…”

The modified Newtonian dynamics—MOND and its implications for new physics

“…Thus started the trend to resolve the acceleration discrepancy by postulating the existence of much dark matter (DM) in systems ranging from the very tenuous dwarf spheroidal galaxies with visible masses ∼ 10 7 M ⊙ to the great clusters of galaxies with observed masses in the 10 14 M ⊙ ballpark [2], in brief in any system where an acceleration discrepancy exists. The DM's role is to provide the missing gravitational pull to account for the excessive accelerations (an easy introduction to the DM paradigm is provided by Khalil and Muñoz [3]). But thirty years of astronomical exploration and laboratory experiments [4] have yet to provide independent evidence of DM's existence, e.g.…”

Late universe dynamics with scale-independent linear couplings in the dark sector

“…The overall density of the observed universe, the growth of structures and their clustering properties cannot be explained by known forms of matter and energy [1,2]. In addition, cosmic microwave background (CMB) anisotropy observations show that the total density is close to critical, so that the gap between known and unknown cannot be accounted for by curvature [3,4].…”