Phase transitions in quark-gluon matter

If the local color symmetry in a quark-gluon matter is broken, the expectation value of the gluon field 〈$A_{\mu }^a$(x)〉 may be different from zero. Such a gluon-condensed phase has been found in mean field approximation. The gluon-condensed phase is characterized by a static, periodic chromomagnetic field, which is coupled to a periodic spin-color density distribution of quarks and antiquarks. Transitions of first and second order type have been found between the gluon-condensed and normal phases, the latter characterized by the vanishing value of the mean gluon field.