Phase Transition in the Higgs Model of Scalar Fields with Electric and   Magnetic Charges
  Using a one-loop renormalization group improvement for the effective potential in the Higgs model of electrodynamics with electrically and magnetically charged scalar fields, we argue for the existence of a triple (critical) point in the phase diagram ($\lambda_{run}, g_{run}^4$), where $\lambda_{run}$ is the renormalised running selfinteraction constant of the Higgs scalar monopoles and $g_{run}$ is their running magnetic charge. This triple point is a boundary point of three first-order phase transitions in the dual sector of the Higgs scalar electrodynamics: The "Coulomb" and two confinement phases meet together at this critical point. Considering the arguments for the one-loop approximation validity in the region of parameters around the triple point A we have obtained the following triple point values of the running couplings: $(\lambda_{(A)}, g^2_{(A)})\approx(-13.4; 18.6)$, which are independent of the electric charge influence and two--loop corrections to $g^2_{run}$ with high accuracy of deviations. At the triple point the mass of monopoles is equal to zero. The corresponding critical value of the electric fine structure constant turns out to be $\alpha_{crit} = \pi/g^2_{(A)}\approx{0.17}$ by the Dirac relation. This value is close to the $\alpha_{crit}^{lat}\approx{0.20\pm 0.015}$, which in a U(1) lattice gauge theory corresponds to the phase transition between the "Coulomb" and confinement phases. In our theory for $\alpha \ge \alpha_{crit}$ there are two phases for the confinement of the electrically charged particles. The results of the present paper are very encouraging for the Anti--grand unification theory which was developed previously as a realistic alternative to SUSY GUTs. The paper is also devoted to the discussion of this problem. 
L. Laperashvili (ITEP, Moscow, Russia), H. B. Nielsen (NBI,   Copenhagen, Denmark)