Magnetic Charge of the Proton and Neutron

Abstract

EVER since the beautiful discussion by Dirac¹ in 1931 of the monopole—the magnetically charged counterpart of the electron—a great deal of effort has been spent in looking for ib². This effort is all the more valuable as Dirac predicted¹ that the existence of at least one monopole would imply the quantization of electric charge, and that the minimum magnetic charge g on the monopole would have the dimensionless parameter g²/ħc equal to 1 /4α, where α is the fine structure constant 1/137. (Arguments have been given³ to show that the minimum value of g²/ħc is α⁻¹.) This monopole charge is very large, and is expected to give rise to effects of a strength similar to strong interactions. There has been recent evidence of the existence of monopoles⁴, though with a magnetic charge lower than that allowed by Dirac's argument. While the evidence for this is not conclusive, it would seem worthwhile to consider the possibility that monopoles can, indeed, exist with any value of magnetic charge.