  This dissertation aims to deepen the understanding of the primordial
composition of the Universe in the temperature range 300 MeV>T>0.02 MeV. I
exploit known properties of elementary particles and apply methods of kinetic
theory and statistical physics to advance the understanding of the cosmic
plasma.
  Within the Big Bang model, we begin by considering the Universe being a
highly energetic fireball, an ultra-relativistic plasma exhibiting distinct
properties. Fundamental particles such as quarks, leptons, and even heavier
gauge bosons play a crucial role in the understanding of the early Universe.
Our research focuses on the investigation of these fundamental particles as
constituents of the dense Universe plasma during the epoch which transits from
primordial quark-gluon plasma to the era of normal hadron matter, passing
through the decoupling of neutrinos and addressing in detail the
electron-positron antimatter plasma.
