Timeline for Special relativity constrains massless electric dipoles, but not massless magnetic dipoles?
Current License: CC BY-SA 4.0
9 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jul 27, 2018 at 19:18 | comment | added | mike stone | @Ben Crowel I've added a discusion of spin and how it affects this stuff. It's bit technical, but the issue is precisely how to relate the technical stuff to concrete pictures like your popsicle stick. | |
| Jul 27, 2018 at 19:16 | history | edited | mike stone | CC BY-SA 4.0 |
added rather lengthy discussion of relativistic spining partcles
|
| Jul 27, 2018 at 14:29 | comment | added | mike stone | @Ben Crowell I want to answer your question properly -- it is an interesting one, The problem is that the proper answer depends more on the propeties of the spin rather than the charge distribution. Relativistic spin is complicated however. I am going to organise what I understand for the magnetic moment case. I will need to do this offline but once I have it sorted I will post it, and then we can try to relate this to your question about the electctric moment. | |
| Jul 27, 2018 at 1:05 | comment | added | user4552 | Thanks for the correction re symmetry of M and D, but I still don't see the point of your discussion of their components. The point remains that your description of M would hold for D and vice versa, if we took the Hodge dual of F. I just don't see how this answer really gets at the point of the question. | |
| Jul 26, 2018 at 17:01 | comment | added | mike stone | @Ben Crowell Both my $M_{\mu\nu}$ and $D_{\mu\nu}$ are skew-symmetric. The violation of EM duality in the interaction with matter comes from all known particles having at most electric charge, and not magnetic charge. In the absence of matter E&M is exactly self dual. If we did have mag monoples then your argument would be exactly correct also. | |
| Jul 26, 2018 at 16:49 | comment | added | user4552 | This is helpful, thanks for writing it up. I don't think it's particularly relevant or physically important that a magnetic dipole energy is expressed as a contraction of F with and antisymmetric tensor while the electric dipole energy involves a symmetric tensor. We could just as easily have written Maxwell's equations using the Hodge dual *F, in which case the symmetry and antisymmetry would be expressed the other way around. The semiclassical argument is interesting, but it doesn't seem to me to clear up the underlying issues. | |
| Jul 26, 2018 at 15:43 | history | edited | mike stone | CC BY-SA 4.0 |
added 10 characters in body
|
| Jul 26, 2018 at 15:02 | history | edited | mike stone | CC BY-SA 4.0 |
added 64 characters in body
|
| Jul 26, 2018 at 14:57 | history | answered | mike stone | CC BY-SA 4.0 |