Structure Formation After the Era of Cosmic Matter Recombination

Abstract

In an aforegoing paper (Fahr and Heyl, 2021) we have studied in physical details the event of cosmic matter recombination expected at about 400000 years after the Big Bang at cosmic photon redshifts of about zr =1000. It turned out there, that photons taken as surely cooling by permanent increase of their cosmic redshifts, while electrons and protons partly are cooled by Thomson scatter processes with photons, but partly are heated due to the Hubble expansion of the universe. It can be shown, however, that in this cosmic epoch the cooling of electrons and protons is much more effective than the heating, and that a recombination of cosmic matter to neutral H-atoms thus is unavoidable. We then show, however, that the neutral gas atoms do not couple anymore to the cosmic CMB photon field, but instead are subject only to the Hubble migration in velocity space and thus become heated again. The question then poses itself, how cosmic structure formation in a gas with decreasing density and increasing temperature should have been able to take place. Where did the galaxies and clusters of galaxies come from? Looking into the unstable, self-gravitating acoustic oscillation modes we find the answer at what cosmic times which magnitudes of self gravitating critical masses can have been produced that could have sustained till the present times.