Magnetic Monopoles in Grand Unified and Kaluza-Klein Theories

Abstract

The apparent reluctance of the proton to decay into e+π°1 suggests that the superheavy gauge bosons that mediate this process must be heavier than the value predicted by minimal SU(5). Some ways of curing this difficulty within the SU(5) framework have recently been discussed2,3. Alternatively, one may resort to gauge groups larger than SU(5). Indeed, it was pointed out some years ago4 that in grand unified theories (GUTs) with intermediate mass scales, the decay rate for p → e+π° (and for other processes mediated by the superheavy gauge bosons) can be considerably lower than the value(s) given by SU(5).