The Relation of the Dark Hydrogenic Atoms and Ions to the Structure Formation in the Universe

The explanation of a puzzling observation at the EDGES facility (in 2018) of the redshifted 21 cm spectral line from the early universe, where it was found that the absorption in this line was about two to three times stronger than predicted by the standard cosmology, and thus the primordial hydrogen gas was significantly cooler than predicted by the standard cosmology, required some kind of baryonic dark matter (DM) as the cooling agent. Then, in our paper published in 2020, both qualitative and quantitative explanations of the puzzling observation at the EDGES were given based on the specific DM in the form of the second flavor of hydrogen atoms (SFHA), corresponding to the 2nd solution of the Dirac equation for hydrogen atoms. In distinction to exotic hypothetical particles previously suggested as the explanation (the particles never discovered experimentally), the existence of the SFHA is evidenced by three different types of atomic experiments, plus it completely resolved the long-standing puzzle of the neutron lifetime. In the latter, the central point was that the two-body decay of neutrons produces—with overwhelming probability—the SFHA rather than the usual hydrogen atoms. The primary property of the SFHA is that, since they have only the S-states, then according to the selection rules of quantum mechanics they cannot emit or absorb the electromagnetic radiation: they remain dark. In the present paper, as the relation of these results to structure formation in the universe, we provide the chronology of the cosmological formation of the surplus of the SFHA (compared to the usual hydrogen atoms) from the recombination epoch through the structure formation epoch, including the production of the SFHA by some neutron stars. Therefore, the halos of modern galaxies contain more of the SFHA than the usual H-atoms. In addition, there is evidence from atomic experiments of the existence of the second flavor of He+ ions (SFHeI). They are also dark due to the selection rules of quantum mechanics. There occurred the cosmological formation of the surplus of the SFHeI (compared to the usual He+) similarly to the surplus of the SFHA. Therefore, the halos of modern galaxies also contain more of the SFHeI than the usual He+. From atomic experiments, it follows that the most probable value of ratio (SFHA + SFHeI)/(usual H + usual He+) is 1.8. From astrophysical observations it follows that the most probable value of the ratio (baryonic DM)/(luminous baryons) is 2.1. The comparison of these two ratios shows that the combination of the SFHA with the SFHeI seems to constitute about 80% of all baryonic DM in the current epoch. It is important to emphasize that the discovery of the SFHA and the SFHeI was based on the standard Dirac equation of quantum mechanics without going beyond the Standard Model, without any change of physical laws, and without any model assumptions, in distinction to the overwhelming majority of hypotheses on DM.