Talk:Interpretations of quantum mechanics/Archive 1

message: Why is a Yes or No desirable?
It seems to me that it does not make sense to presuppose that all "yes"es in the table is desirable. Nature is the way she is.
I think the last 2 paragraphs should be removed (or significantly changed) 
Oz 04:00, 13 Sep 2003 (UTC)
thread_title:  Why is a Yes or No desirable? 

message: One has to define for any interpretation (whether it is understood as a formal equivalence or an ontological one) what it means for that interpretation to have the properties of "reality", "completeness" etc. I am treading on dangerous waters here.
I also agree that the Feynman dictum should be put back in.  I only meant to remove the phrase "neutral interpretation".  CSTAR 16:47, 16 Jan 2005 (UTC)
thread_title:  Philosophical problems

message: I suggest changing the sentence
: are described by real numbers nd there does not seem to be any need to provide a special interpretation for these values. A similar comment can made in regard to the understanding of electromagnetism.
: are described by real numbers and functions defined on sets which have direct spatial meaning.  In this case, there does not seem to be any need to provide a special interpretation for these objects . A similar comment can made in regard to the understanding of electromagnetism.
CSTAR 20:26, 9 Feb 2005 (UTC)
thread_title:  Interpretation in classical physics 

message: Could we remove that adverbial phrase at the beginning? Yes I put it in, but at the time it seemed a like a plausible step to set up a transition from the previous content of the page. CSTAR 23:13, 10 Feb 2005 (UTC)
thread_title: In a nontechnical sense

message: Could we delete this sentence or somehow integrate it into another one?  CSTAR 17:44, 19 Feb 2005 (UTC)
thread_title:  very high status as a scientific theory 

message: ----
"later expressed in Richard Feynman's famous dictum: "Shut up and calculate"."  Attribution to Feynman, althought widespread, may be bogus. see http://www.physicstoday.org/vol-57/iss-5/p10.html Mermin is not able to find a reference with a source to Feynman ever saying this, although Mermin said it in 1989  64.165.202.199 22:10, 2 May 2005 (UTC)
replies: text:  Thanks for the tip.  I included your reference into the article.--CSTAR 05:15, 3 May 2005 (UTC)
thread_title:  Shut up and calculate 

message: A recent edit claims that the assertion is disputed.  How is this dispute to be "interpreted". (This BTW is a fairly standard view, e.g., from Omnes).--CSTAR 22:27, 17 September 2005 (UTC)
thread_title:  Disputed claim 

message: Another recent edit asserts that measurement and non-determinism are not within the theory"? Wht not? One of von Neumann's big contributions in his book was the theory of measurement. He made a big deasl out of this. More over every article amnd book I've seen on interpretation of quantum mechanics makes this into a big deal. If not, why are quantum operations important? Is the editor who made the above claim also claiming that these are not part of the theory?--CSTAR 20:59, 18 September 2005 (UTC)
thread_title:  Another edit 

message: "In particular, the bare instrumentalist view of quantum mechanics outlined in the previous section is not an interpretation at all since it makes no claims about elements of physical reality." (see section "properties of interpretations")
The statement above is incorrect. A genuine instrumentalist view would state the following:
"A particular experimental pattern run in a precise configuration (e.g. a Stern & Gerlach experiment with a specific relative orientation between the "green" apparatus and the "red" one) generates a flux of discrete informations whose distribution function over a fixed (potentially infinite) set of values is stable, reproducible at will, valid for any experimentator".
The distribution function is a property of the experimental pattern (this is a tautology and thereby a true statement). Running the experimental pattern results in a measurement of the distribution function. It creates knowledge about a property of the experimental pattern. It adds value if considered within the framework of a theory about experience, about "what it means to be the Actor of an experiment in the world", within the framework of a "phenomenology". This is precisely what "Quantum Theory" is about.
Of its own, the distribution function does not bring any knowledge nor information about "what happens inside the experimental device". It does not add any value if considered within the framework of a physics theory, until it is converted ("interpreted")into a property of our "model" or "simulation" of "how the world is, how it works, what happens there inside the experimental device". 
"In the case of quantum mechanics, the most common instrumentalist description is an assertion of statistical regularity between state preparation processes and measurement processes. This is usually glossed over into an assertion regarding the statistical regularity of a measurement performed on a system with a given state φ." (see section "instrumentalist interpretation")
Stating that the information gathered through participating into an experiment is "about a system", meaning "about something in the world" is already the result of an interpretation for which conversion rules have not been defined. This statement is neither true nor false: it simply cannot be falsified or verified by an experiment.            SUGDUB  (07 Sept 2005)
: Your formulation seems like an extremely radical form of instrumentalism. A more traditional function of instrumentalism is to reconcile divergent models of observations: for example, an earth-centrist might consider a copernican model of the universe as a useful theoretical tool (or instrument)   to make calculations and predictions. Am I mistaken? --CSTAR 19:24, 8 October 2005 (UTC)
replies: text:  You can certainly add such a section. --CSTAR 02:27, 13 October 2005 (UTC)
replies: text: I suggest a distinct article on the instrumentalist interpretation. linas 18:12, 23 October 2005 (UTC)
replies: text:  Done. I started with a "factual" description of the S&G experiment, alongside the above. Larmor's experiment should follow. However the section title is misleading, since the aim is to avoid any interpretation, trying to stick to facts. (SUGDUB - 01/11/2005)
To quote from Einstein, "I don't undrstand it.".
David R. Ingham 03:21, 15 October 2005 (UTC)

text:  You'll have to me more specific: You don't understand what? --CSTAR 03:26, 15 October 2005 (UTC)

text: Well you are  pointing to the fact that much of what is regarded as interpretation is an artifact of history, a transitional intellectual activity. I prefer Axiomatic quantum mechanics myself.--CSTAR 05:27, 24 October 2005 (UTC)
thread_title:  On the aboutness of Quantum Theory 

message: H0riz0n: How about "Quantum philosphy" why was it deleted and redirected WITHOUT DEBATE? I had put up the page put the "Wiki Control Group" against alternative views. Deleted it and redirected it here. Quantum Philosophy isnt "interpretation" its applying philosphical and theoogical interpretation into the realm of QM and Quantum Cosmology. Quantum Philosoper are making far reaching interpretations of QP into the realm of theology and philosophy.  That is why such discussion is not merrited to this page because Interpretation ISNT philosphy.
:This act of redirection is being discussed at Wikipedia_talk:WikiProject_Physics#New_.26_interesting and whether to merge with Quantum mysticism. Please move discussion there. GangofOne 05:46, 6 April 2006 (UTC)
thread_title: Quantum philosophy

message: Might it be better to change the instrumentalist view to talk more about expectation values instead of wave functions?  This is because the former are "real" in that they're measureable, whereas the latter are the subject of interpretation.  Thus, I propose that the text would be something like the below, prettied up. It has a side benefit of cleaning up the math and making the math less akward (in my opinion):
:An arbitrary (pure) state of the system may be represented by a wave function ψ. When an experimenter chooses to measure some observable A, then the outcome of the experiment is given by the expectation value of A with repsect to ψ. To compute this expectation value, the theory states that ψ is an element of a vector space, and that it must be written in a vector space basis
::\vert \phi_1 \rangle, \vert \phi_2 \rangle, \cdots
:of eigenstates of A, where an eigenstate is a vector satisfying
::A\vert \phi_n \rangle = \lambda_n \vert \phi_n \rangle 
:for some real number \lambda_n. To compute the outcome of the experiment, the state of the system ψ must be decomposed as
::\vert \psi \rangle = c_1 \vert \phi_1 \rangle + c_2 \vert \phi_2 \rangle + \cdots
:with some certain specific complex numbers c_n resulting from that decomposition.  The outcome of the experiment is then nothing more than the expectation value of A, which is given by the expression
:: \langle \psi \vert A \vert \psi \rangle = c_1^* c_1 \lambda_1 +
c_2^* c_2 \lambda_2 + \cdots
:This experimentalist view gives a simple, direct way to compute the outcome of an experiment. To compute the outcome, there is no need to inquire into the meaning of the numbers c_n or \lambda_n; they are merely components of a formula where only the final value matters.
Optionally, have also the following paragraph (which I think is superfluous) but:
:The probability of finding the system in a given state \vert\phi_n\rangle is given by computing the expectation value of the projection operator
::\Pi_n = \vert\phi_n\rangle \langle \phi_n \vert
:The probability is then the non-negative real number given by
::P_n = \langle \psi \vert \Pi_n \vert \psi \rangle = c_n^* c_n = \vert c_n\vert^2
:The sum total of probabilities of finding the system in a state \phi_n must add up to a total of one:
::P_1 + P_2 + \cdots = 1 
I think that this might bring the math closer to actual practice/education, as well as minimizing discussion of the wave function (which, I believe, is what the instrumentalists do). Also, I believe the math above is no harder than what the article currently contains, right? And its more edifying, as it reminds the reader that QM plays out entirely on vector spaces. linas 14:40, 24 October 2005 (UTC)
replies: text: I have no objection. --CSTAR 15:09, 24 October 2005 (UTC)

text: In the instrumentalist point of view, QM is understood to be a set of calculations to be performed on a complex-valued vector space, of finite or possibly infinite dimension. The state of a system to be measured corresponds to a vector in this vector space. Experiments perform measurements on observables, where observables correspond to Hermitian matrices. The result of a measurement is given by the expectation value \langle \psi \vert A \vert \psi \rangle where ψ was the vector, and A was the observable.
This is much briefer, maybe more appropriate? Or do you prefer the long version? linas 14:22, 25 October 2005 (UTC)
replies: text:  I liked your longer version.--CSTAR 14:59, 25 October 2005 (UTC)
replies: text: OK, I've merged it in. Somehow, it got slightly more verbose. Fix/critique as needed.linas 22:21, 27 October 2005 (UTC)

text:  It is longer, but that's the nature of the beast. And it's more in line with the educational system as you point out.--CSTAR 03:11, 28 October 2005 (UTC)
thread_title:  Fix for instrumentalist view 

message: A change [] has been suggested that would re-name and re-classify this article.
: The suggested change is a bad idea, in my opinion. That article has problems of its own, documented there.--CSTAR 13:09, 26 October 2005 (UTC)
replies: text: Agree with CSTAR. That other article is highly unusual, bordering on original research; it needs to be fixed first. Its also not at all about classical physics.  linas 14:30, 26 October 2005 (UTC)
thread_title:  Organization and the place of this artcle 

message: Re: Edit summary:I'm not sure what that sentence was trying to say, but hopefully now it's clearer
What it was trying to say, was I though pretty clear: 
* Quantum mechanics is succesful
* Some people (Philosophers of science, -- some people) argue over what it means (whether this is in fact what they're arguing about  is itself subject to argument).
* This requires some  explanation
Now you may argue that's a non-sequitur, but then you should fix the non-sequitur. --CSTAR 19:52, 26 October 2005 (UTC)
replies: text:  Actually you (User:Laurascudder) may want to rewrite the whole intro. Although I suggest that the Jankiw and Kleppner quote be kept. --CSTAR 20:10, 26 October 2005 (UTC)
thread_title:  Edit of intro

message: "In fact, the notion that the state vector collapses to a particular value of a variable "at a given instant" is inconsistent with the transactional description." quote from  Cramer's own description of his interpretation. Wouldn't this mean that there is no wavefunction collapse in transactional interpretation in contradiction with what the diagram claims? --MarSch 14:00, 2 November 2005 (UTC)
replies: text: That diagram is highly suspect. --CSTAR 14:16, 2 November 2005 (UTC)
replies: text: It appears so. Transactional interpretation is also not deterministic.--MarSch 16:08, 2 November 2005 (UTC)
replies: text:  Blow it away, if you want.--CSTAR 16:11, 2 November 2005 (UTC)
replies: text:  Changed to non-deterministic --Michael C Price 13:42, 13 June 2006 (UTC)
thread_title:  no wavefunction collapse in transactional interpretation