This book introduces quark gluon-plasma (QGP) as a primordial matter composed of quarks and gluons, created at the time of the Big Bang. After a pedagogical introduction to gauge theories, various aspects of quantum chromodynamic phase transitions are illustrated in a self-contained manner. The cosmological approach and renormalization group are covered, as well as the cosmological and astrophysical implications of QGP, on the basis of Einstein's...