# Questions abot magnetic monopoles

1. Mar 25, 2012

### johne1618

If magnetic monopoles exist:

1/ Would there be two types: North and South?

2/ If a monopole was a fermion would it have an intrinsic electric dipole moment (in analogy to normal charged fermions that have an intrinsic magnetic dipole moment)?

3/ Could the cosmological dark matter be made of monopoles?

2. Mar 25, 2012

### tom.stoer

1) yes

2) I don't think they can be fermions; when plugging them into the Maxwell equations as a source term (like the charge density) then they must be scalars

3) I don't think so, b/c there seems to by a lot of dark matter and therefore we should have observed a couple of monopoles

3. Mar 26, 2012

### Khashishi

I don't see anywhere in the Maxwell's equations that they must be scalars. We don't know of any scalar particles. I would expect magnetic monopoles (if they exist) to be like magnetic electrons, in which case they ought to have an intrinsic electric dipole moment.

4. Mar 26, 2012

### Bill_K

This paper by the D0 collaboration sets mass limits on magnetic monopoles with spin 0, ½ and 1. So a magnetic monopole with spin is considered a possibility, to an experimentalist at least.

5. Mar 27, 2012

### tom.stoer

So about that; I must have been drunk when writing this. Of course the r.h.s. of the
Maxwell equation is not a scalar but a four-vector with a magnetic charge and a magnetic current density.

The usual approach is to introduce monopes on the r.h.s. of the Maxwell equations, just like the charge density. If you do it that way the behavior w.r.t. Lorentz transformations rule out anything else but four-vectors.

If you compare it to electron fields (like in QED) you have to remember that charge and current densities are bilinear in the spinor fermion fields, so spinor indices are contracted to form a four-vector. If you want to introduce a spinor field you have to construct an object (at least) bilinear in the spinors to plug it into the Maxwell equations.

6. Mar 29, 2012

### johne1618

Could a North and South monopole form a bound state cancelling out the magnetic charge?

I guess such a bound state would be harder to detect.

Last edited: Mar 29, 2012