arXiv1999
The electroweak phase transition in the magnetic and hypermagnetic fields is studied in the Standard Model on the base of investigation of symmetry behaviour within the consistent effective potential of the scalar and magnetic fields at finite temperature. It includes the one-loop and daisy diagram contributions. All discovered fundamental fermions and bosons are taken into consideration with their actual masses. The Higgs boson mass is chosen to be in the energy interval 75 GeV $\le m_H \le$ 115 GeV. The effective potential calculated is real at sufficiently high temperatures due to mutual cancellation of the imaginary terms entering the one-loop and the daisy diagram parts. Symmetry behaviour shows that neither the magnetic nor the hypermagnetic field does not produce the sufficiently strong first order phase transition. For the field strengths $H, H_Y$ $\ge 10^{23}$ G the electroweak phase transition is of second order at all. Therefore, baryogenesis does not survive in the Standard Model in smooth magnetic fields. The problems on generation of the fields at high temperature and their stabilization are also discussed in a consistent way. In particular, it is determined that the nonabelian component of the magnetic field $ (gH)^{1/2} \sim g^{4/3}T$ has to be produced spontaneously. To investigate the stability problem the $W$-boson mass operator in the magnetic field at high temperature is calculated in one-loop approximation. The comparison with results obtained in other approaches is done.