Stable Grand-Unified Monopoles with Multiple Dirac Charge

Abstract
Magnetic monopoles with multiple Dirac charge are found to be stable in grand unified theories with symmetry breaking by an adjoint Higgs field under certain conditions. In the SU(5) model, the double, triple, quadruple, and sextuple monopoles are stable for a range of parameters in the Higgs potential. The effects of electroweak symmetry breaking on multiply charged monopoles are discussed. Evidence is also presented for the existence of a stable nonspherically symmetric quadruple monopole.