Supercooling in the SU(5) phase transitions and magnetic-monopole suppression

We demonstrate that there exists a range of values of parameters which leads to a supercooled transition from the symmetric SU(5) phase to the asymmetric SU(3)×SU(2)×U(1) phase when the scalar quartic coupling constants in the Higgs potential are $O\left(g^4\right)$, $g$ being the gauge coupling constant. We find that the transition is supercooled throughout most of the light Higgs region. These results are compared with the results of phase transitions in the standard model of electroweak interactions, and are shown to lead to magnetic-monopole suppression, but other serious problems arise.