Once More on a Colour Ferromagnetic Vacuum State at Finite Temperature

The spontaneous vacuum magnetization at finite temperature is investigated in SU(2) gluodynamics within a consistent effective potential approach including the one-loop and the correlation correction contributions. To evaluate the latter ones the high temperature limits of the polarization operators of charged and neutral gluon fields in a covariantly constant magnetic field and at high temperature are calculated.The radiation mass squared of charged gluons is found to be positive. It is shown that the ferromagnetic vacuum state having a field strength of order $(gH)^{1/2} \sim g^{4/3} T$ is spontaneously generated at high temperature. The vacuum stability and some applications of the results obtained are discussed.Comment: 16 pages, 2 figures, subm. to Nucl. Phys.

Ring diagrams and electroweak phase transition in a magnetic field

Electroweak phase transition in a magnetic field is investigated within the one-loop and ring diagram contributions to the effective potential in the minimal Standard Model. All fundamental fermions and bosons are included with their actual values of masses and the Higgs boson mass is considered in the range $75 GeV \leq m_H \leq 115 GeV$. The effective potential is real at sufficiently high temperature. The important role of fermions and $W$-bosons in symmetry behaviour is observed. It is found that the phase transition for the field strengths $10^{23} - 10^{24}$G is of first order but the baryogenesis condition is not satisfied. The comparison with the hypermagnetic field case is done.Comment: 16 pages, Latex, changed for a mistake in the numerical par