Primordial magnetic field generation in the Quark Gluon Plasma phase
  In this work we investigate the possibility of generation of primordial
magnetic field in the early universe near the QCD phase transition epoch via
the collapse of $Z(3)$ domains. The $Z(3)$ domain walls arise in the deconfined
phase of the QCD (above $T\sim 200$ MeV) and their collapse leads to a net
quark concentration near the wall boundary due to non-trivial reflection of
quarks. We look at the response of leptons to this quark excess and find that
leptons do not cancel the electric charge concentration due to the quarks. The
wall collapse and a net charge concentration can lead to the generation of
vorticity and turbulence in the primordial plasma. We estimate the magnitude of
the magnetic field generated and find that it can be quite large
$\mathcal{O}(10^{15-18}\mathrm{G})$. The mechanism is independent of the order
of the QCD phase transition.
