The destiny of an antiparticle

[ohwilleke]

After this interaction with Bob, she will entangle her bodystates with his (mmm:-)

Somebody is way, way too hard up.

More seriously, thanks for bringing the MWI into the discussion. I personally don't like the MWI, but your example does a good job of illustrating its intepretive power.

 

[vanesch]

More seriously, thanks for bringing the MWI into the discussion. I personally don't like the MWI, but your example does a good job of illustrating its intepretive power.

Personally, I evolved from rather anti-MWI to quite in favor of it, for several reasons, the most important being:
- all current attempts at incorporating gravity (string theory, loop quantum gravity) seem to take the superposition principle very seriously - although I think that the jury is still out on this.
- symmetry principles of which the guiding importance in physics cannot be denied are respected throughout the entire theory, which is not the case for any other formulation of quantum theory (copenhagen, or Bohm).

Nevertheless, I'm a heretic in the MWI camp, in the sense that I think that the probability rule (Born rule) does NOT follow automatically from the unitary evolution ; I even recently submitted a paper concerning this
(see http://perso.wanadoo.fr/patrick.vanesch/articles/borneverett.pdf). I think the Born rule IS an extra postulate which describes the ontological/epistemological transition.

However, I don't know how seriously I have to take it - as I pointed out already in the past, every century or so, our paradigms change, so it would be pretentious to think that we now reached "the end" and have "the right" paradigm: 300 years from now, our vision will be totally different in any case.

But I think that MWI, even just as a formal game, has the possibility of enlightening the understanding of a lot of "quantum mysteries", of which EPR setups and delayed choice quantum erasers are examples.

Especially the locality issues in the EPR case are well illustrated: it is to my knowledge the only explanation which clearly puts forward both facts: the clear observation of correlations, and the impossibility of making FTL telephones using the phenomenon. It also helps resolve issues of "when do we apply the collapse".
So I think that in this context, MWI has its place just as Bohm's theory has its place, as _examples_ of what is often claimed is not possible :-)

cheers,
Patrick.

 

[El Hombre Invisible]

Ahem. I won't pretend that any of that didn't go over my head, though I'm trying to get that link opened right now. I just had a thought relating to a point I asked about earlier - that is, is there any reason why the photon emitted has to be twice the energy of the original electron or, to put it another way, does the speed of the positron have to be the same as the electron? Would I be right in saying they would have to be equal, as momentum must be conserved in pair creation? Having said that, if the speeds weren't equal, could the relativistic momentum of the photon make up the difference? Thanks. Sorry for interrupting. What is MWI? Mars War One?

 

[masudr]

The momentum has to be conserved in any interaction, and so the momentums of both the electron and positron have to be equal and opposite. MWI = Many worlds interpretation (but I'm guessing if you didn't know it already, me telling you wouldn't help too much (:, look it up on the web, in your local library etc).

 

[El Hombre Invisible]

Sounds far out. I'll dig around. I tried to understand Patrick's explanation and I am thinking that, in words an undergrad can understand, the point is that the information isn't being transmitted instantaneously because to compare the results of a change to one of the entangled pair with the other, somebody or something has to travel between the two (such as Alice radioing Bob or vice versa) and it is this medium by which the information crosses..? If not, I'll... try again in a few years. ;o)

Thanks to all for your help with the pair problem. I think it has kind of brought me round full circle, as although Feynman's approach seems to yield a satisfactory explanation for spontaneous pair creation and annihilation, it does seem to depend equally coincidentally on the amount of energy released (forwards or backwards in time). Ultimately neither interpretation seems free of what I believe are scientifically known as niggles.