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Dirac gave an argument once upon a time showing that quantization of angular momentum together with the presumed existence of a magnetic monopole implies quantization of charge. If there is, anywhere in the universe, a magnetic monopole of magnetic charge [itex]Q_m[/itex], then the only possible values for the electric charge of a particle are:
[itex]Q_e = \dfrac{n \hbar}{Q_m}[/itex]
(or something like that). So there is some smallest charge, [itex]Q_0[/itex], and every other charge must be an integer multiple of that.
My question is how this applies to composite particles such as the proton. Let's assume (contrary to any evidence) that there is a magnetic monopole, so by Dirac's argument, charge is quantized.
If you have a composite particle made up of smaller particles, is it that the total charge must be a multiple of [itex]Q_0[/itex], or must every constituent particle be a multiple of that minimum charge? More specifically, is it possible that the minimum charge is the charge on the electron, rather than the charge on the quark (which is 1/3 or 2/3 the electron's charge).
I'm guessing the latter, but I don't know whether Dirac's argument depends on the field of the electric charges being long-range (the electric field due to quark charge isn't, since quarks always appear in combinations with integral charge).
[itex]Q_e = \dfrac{n \hbar}{Q_m}[/itex]
(or something like that). So there is some smallest charge, [itex]Q_0[/itex], and every other charge must be an integer multiple of that.
My question is how this applies to composite particles such as the proton. Let's assume (contrary to any evidence) that there is a magnetic monopole, so by Dirac's argument, charge is quantized.
If you have a composite particle made up of smaller particles, is it that the total charge must be a multiple of [itex]Q_0[/itex], or must every constituent particle be a multiple of that minimum charge? More specifically, is it possible that the minimum charge is the charge on the electron, rather than the charge on the quark (which is 1/3 or 2/3 the electron's charge).
I'm guessing the latter, but I don't know whether Dirac's argument depends on the field of the electric charges being long-range (the electric field due to quark charge isn't, since quarks always appear in combinations with integral charge).