Talk:Wave function/Archive 4

Archive 1

Archive 2

Archive 3

Archive 4

Archive 5

Archive 6

→

Archive 10

Lead edits

It's just my opinion, although recent edits to the lead seem to have gone backwards in clarity.

1. Sbyrnes321 beat me to this at the end of this section. I don't know what a "quantum analyzer" is (a hypothetical or real particle detector?), and it was clearer to get the point across quickly and say "the wavefunction is a function of the all the position coords and time, or momenta and time" etc.
2. A previous concern by Quondum here was mathematical. Is the codomain of the wavefunction always the complex numbers? The statement "However, complex numbers are not necessarily used in all treatments" has been deleted.

It is tempting to revert back to this lead version, but others should input first. M∧Ŝc²ħεИ_τlk 17:57, 3 January 2015 (UTC)

Input. YohanN7 (talk) 18:49, 3 January 2015 (UTC)

To be a bit more precise. Chjoaygame, what is the point of rewriting the lead in an archaic style so that instead of the occasional lay-reader not understanding it, now nobody understands it? This is not the place to invent terminology. Even if Bohr and others might have used it, the language and tone of the early 1900's is inappropriate and not quite penetrable if you want to know what QM is about. It perhaps makes the thing easier to read, but it comes with the price of making it impossible to understand. If we have to compromise between readability and correctness, then correctness will always come out on top. An article about QM that makes you feel good because you understood every single word (in isolation) isn't necessarily good. YohanN7 (talk) 19:05, 3 January 2015 (UTC)

It seems, I know what is meant by "analyzers". Just observables. In the same spirit as I wrote in the previous section: 'it is hardly a good idea, to fix once and for all the "right" collection of "physically natural" observables'. Coordinates, yes; momenta, yes; but any other observable, still yes, provided that its spectrum is of multiplicity 1 (the squared momentum does not fit, for instance). Boris Tsirelson (talk) 19:28, 3 January 2015 (UTC)

Regardless, the whole lead is not better than it was before. "Quantum analyzer" is not a common term and isn't helpful when you can just say "observable", which is standard and useful terminology.

Just to add to my point 2 above: currently the lead now merely states:

"Other treatments of quantum physics have been proposed, for example by Louis de Broglie.[6]"

which is not helpful since yes there are other formulations of QM, but this is not the point. For this article it should state wavefunctions are not always complex-valued.

Also Chjoaygame, could we keep the discussion in this section from this point forward? Thanks, M∧Ŝc²ħεИ_τlk 19:40, 3 January 2015 (UTC)

"I don't know what a "quantum analyzer" is (a hypothetical or real particle detector?)" It's the device that splits the beam into eigenstates that are sent to their respective detectors, as noted above.

I have undone my edit as suggested by Maschen.

I was driven to make the now undone edit because I think the lead should make the point that the wave function must be defined with respect to the possible measurements. For example London and Bauer (1939): "The wave function it uses to describe the object no longer depends solely on the object, as was the case in the classical representation, but, above all, states what the observer knows and what, in consequence, are his possibilities for predictions about the evolution of the object. For a given object, this function, consequently, is modified in accordance with the information possessed by the observer."<translation by Wheeler, Zurek et al., page 218 of Wheeler and Zurek 1983.> I read the latter as a paraphrase of Bohr's injunction. In mathematical terms that translates to a requirement for the mathematical existence of at least one basis that refers directly to physical existence. London and Bauer's "modification" of the wave function is not an adjustment of its values; it is a restructuring of its functional nature. Also I think that it should be made clear that QM "measurement" is not measurement in the ordinary language sense, as emphasized by Bohr.Chjoaygame (talk) 20:18, 3 January 2015 (UTC)Chjoaygame (talk) 20:47, 3 January 2015 (UTC)

For reference here is the reversion.

Thanks, we do appreciate the good faith efforts, but writing something along historical lines is not usually helpful, since interpretations, terminology etc. moves on. It's just that overall, the writing was not well-written, right at in beginning paragraph you wrote about "adventures" (...??).

About "quantum analyzers", I started this thread at 17:57, you posted in this section at 18:21, so I hadn't seen what you meant. M∧Ŝc²ħεИ_τlk 20:54, 3 January 2015 (UTC)

For the last point of Maschen, which is really an aside in this thread, there is no need at all to in the lead make the point that wave functions aren't necessarily complex valued under exceptional circumstances. The exceptions fall into two classes. The first class are exceptional circumstances where the imaginary part happens to vanish (Some 1-d problems, Majorana fermions in a certain basis). No mention needed. The second class is when a mathematical framework is used to transform the complex wave functions (and the machinery, including the Schrödinger/Dirac/Whatever equations) to a more complex domain, such as the domain of geometric algebra. (Ironically, this case is covered by complex valued wave functions.) Neither of these exceptions need to be mentioned in the lead. Why? Well, the reader might ask - if the wave function isn't a vector of complex numbers, then what the hell is it? This is not the place to elaborate on such questions. This is making something difficult more difficult. Connoisseurs of geometric algebra might object, but introducing GA in the lead here is overdoing it. The wave function is always an array of complex-valued functions. The fact that you can turn it to something else in a one-one fashion is immaterial. If that wasn't the case, most every lead needs to be rewritten. YohanN7 (talk) 20:35, 3 January 2015 (UTC)

Agreed.Chjoaygame (talk) 20:41, 3 January 2015 (UTC)

I was trying to not exclude other formulations of QM or mathematical machinery. If people want to cut that part out entirely that's fine, up to them, just write it clear so that no-one will ask the question again in future. M∧Ŝc²ħεИ_τlk 20:54, 3 January 2015 (UTC)

I know of the previous discussion, and I thought myself the wording was an okay compromise back then. I have cut it out because I no longer think it is okay (too demanding for the reader). The place to reintroduce it is in a new subsection of one of the mathematical sections as just one more formalism. YohanN7 (talk) 21:09, 3 January 2015 (UTC)

I also removed the de Broglie-Bohm theory from the lead. It presence seemed to be motivated by that real numbers were used as opposed to complex numbers. (My taking is that de Broglie-Bohm theory is something over and above ordinary QM and has little to do with how it is represented in terms of numbers.) YohanN7 (talk) 21:20, 3 January 2015 (UTC)

Chjoaygame I think some of your edits have been good, just out of place. Some of it (the Stern-Gerlach thing) could, if edited, go elsewhere. But here is another point, "... the wave function must be defined with respect to the possible measurements...". No, this is not so. The interpretation of the wave function might have to be associated with something we can measure (or it wouldn't be accepted as an interpretation), but this is all POV. Granted, it is the POV of some great minds, but it isn't necessary to develop QM to involve measurements. YohanN7 (talk) 21:40, 3 January 2015 (UTC)
(Here's my POV: Nature couldn't care less whether we measure it or not. YohanN7 (talk) 21:42, 3 January 2015 (UTC))

And mine: Nature measures itself in some situations, and does not in others, and this makes the quantum/classical interface; we are just one form of decoherence makers. Boris Tsirelson (talk) 06:47, 4 January 2015 (UTC)

What you say here needs some replies, but not here and now. According to Feynman, nobody understands QM.Chjoaygame (talk) 00:06, 4 January 2015 (UTC)

And he was right. YohanN7 (talk) 01:39, 4 January 2015 (UTC)

I've not seen the history of edits, and the controversial assertion that measurement is intrinsic to the definition of a wave function clearly cannot be made. To make this assertion would be to imply that the concept would not apply at all in the many-worlds interpretation. This is enough reason to exclude it. —Quondum 16:56, 4 January 2015 (UTC)

Archiving

I might have screwed up when putting a MiszaBot template here. It did archive, but the gods themselves only know to where. YohanN7 (talk) 00:50, 12 January 2015 (UTC)

It filled up an old archive, Archive 2, then created Archive 3. Stuff still here. YohanN7 (talk) 11:02, 12 January 2015 (UTC)