ctamblyn
Data Ghost
OK, but pictures can be dangerous. Look at the E-field in (a) - an impression is created that a line of E begins at the strip, and then extends outwards normal to the strip. Of course, we both know (and I'm sure that Williamson and van der Mark know this too) that the line of E does no such thing. Rather, we should perhaps picture it as passing through the strip, extending infinitely far in a straight line in both directions.I really think you're reading too much into that. The twisted strip marked a)
[qimg]http://members.optushome.com.au/walshjj/toroid1.jpg[/qimg]
..is just a re-presentation of the typical depiction of a circularly polarised light wave:
[qimg]http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/imgpho/polcir.gif[/qimg]
http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/polclas.html
The reason for pointing this rather obvious fact out, is that in the closed path picture (b), Williamson and van der Mark are, I contend, incorrect in asserting that the E-field vector is "radial and directed inwards", at least on the basis of the topology they're considering. Actually there's a very general argument that covers a wide range of spatial topologies, and in outline it's like this:
Consider a self-trapped photon, and picture in your mind a closed surface which contains it. Now suppose that there is a non-zero flux of E through that surface (let's imagine the flux is negative, so we have a negative apparent charge). If this is the case, then select a line of E and follow it in through the surface, and into the heart of the self-trapped photon system. Where does it go? I think we'd agree that photons cannot be a field-line terminus (correct me if I'm wrong), so the line of E must do one of two things:
- Disappear down a hole. If you could arrange for a funnel to connect two distant points in space, then lines of E could disappear down one end of the funnel and emerge from the other end. You'd appear to have two equal, yet opposite charges.
This may seem attractive (ETA: no pun intended), but the problem is that the spatial topology here would be just as capable of generating magnetic monopoles as electric ones (it's that old problem again). Depending on the radius of the funnel opening, maybe you could also observe things seeming to "vanish" as they fall in - not, I imagine, what you're after. - Re-emerge. The situation then is that there is actually zero net flux through our surface, and so the contained system is electrically neutral.
Hopefully my comment above has addressed this.The figure-of-eight at b) is just a stepping stone to the torus with the dark line, see http://members.optushome.com.au/walshjj/toroid2.jpg.
I prefer to reserve the term "curvature" for the geometric concept - the stuff that makes parallel transport around closed curves non-trivial and, therefore, interesting.OK. I'd say there's a topology to the electron, and a curvature to the photon, but let's not get bogged down with the distinction.
The distinction mainly mattered if you were claiming that the stress-energy-momentum of the photon field corresponds to the spacetime geometry which causes the confinement - at least, if this is happening in a manner consistent with GR. I don't think this is what you're claiming at this stage, however.
Ah, I remember the joy of having a two-year-old. I hope he's all better now.Commiserations. The wife and I have a two-year-old, and he's a little unwell at the moment. Nothing serious, just a coughy cold. But said wife has been out this afternoon, shopping, and young sir has been having a bad day.
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