Questions abot magnetic monopoles

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Discussion Overview

The discussion revolves around the theoretical existence of magnetic monopoles, exploring their properties, potential types, and implications for cosmology, particularly in relation to dark matter. Participants examine the nature of monopoles in the context of Maxwell's equations and their possible characteristics as particles.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that if magnetic monopoles exist, there would be two types: North and South.
  • One participant suggests that if a monopole were a fermion, it might have an intrinsic electric dipole moment, similar to charged fermions with intrinsic magnetic dipole moments.
  • Another participant argues against the possibility of monopoles being fermions, stating that they must be scalars when included in Maxwell's equations as a source term.
  • A participant challenges the scalar requirement, asserting that there is no evidence for scalar particles and suggesting that monopoles should behave like magnetic electrons, potentially possessing an intrinsic electric dipole moment.
  • Reference is made to a paper by the D0 collaboration that sets mass limits on magnetic monopoles with various spins, indicating that monopoles with spin are considered a possibility.
  • One participant questions whether a North and South monopole could form a bound state that cancels out the magnetic charge, noting that such a state might be harder to detect.
  • Concerns are raised about the abundance of dark matter and the implications for the existence of monopoles, suggesting that if they were common, they should have been observed by now.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of magnetic monopoles, their potential properties, and their implications for dark matter. The discussion remains unresolved, with no consensus reached on the characteristics or existence of monopoles.

Contextual Notes

Participants reference various assumptions about the nature of monopoles and their treatment in theoretical frameworks, including the implications of Maxwell's equations and the characteristics of potential monopole particles. There are unresolved questions regarding the definitions and properties of monopoles as they relate to existing physical theories.

johne1618
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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?
 
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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
 
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.
 
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. :smile:
 
Khashishi said:
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.
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.
 
tom.stoer said:
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

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.
 
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