Gravity in the early universe

Abstract

According to scientific evidence, the universe began after the “Big Bang” with a very high temperature and energy density. At early times, the temperature was certainly so high that all particles such as quarks, leptons, gluons, and so forth were strongly relativistic. Even strongly interacting quark and gluon particles interact relatively weakly due to asymptotic freedom. Therefore, it was only a system of hot and weak particles that can be called Quark-Gluon Plasma. As the universe cooled during the next phase of expansion, quarks, antiquarks, and gluons combined to form hadrons, leading to the formation of baryonic matter, the phase transition of quantum color dynamics (QCD), during which quarks and gluons are confined. In the first-order cosmic phase transition with the formation of bubbles, the transition to a true vacuum occurs. The bubbles expand and collide with each other, and part of the energy stored in the walls of the bubbles turns into gravitational waves.