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Author Topic: What do you think about the wave function collapse?  (Read 7934 times)

Offline PmbPhy

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I came across this thread https://www.quora.com/What-does-it-mean-to-say-a-wave-function-collapses at the Quora forum. The first person on the list writes: When people say that "the wavefunction collapses", that means that they don't understand how quantum mechanics works.  Frankly I find comments like that not only rude but ignorant and the person who says it being arrogant. Most textbooks speak of the collapse of the wave function.

To be clear on what it means see: Wave function collapse at
https://en.wikipedia.org/wiki/Wave_function_collapse
Quote
In quantum mechanics, wave function collapse is said to occur when a wave function—initially in a superposition of several eigenstates—appears to reduce to a single eigenstate (by "observation"). It is the essence of measurement in quantum mechanics and connects the wave function with classical observables like position and momentum.


 

Offline Thebox

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Re: What do you think about the wave function collapse?
« Reply #1 on: 08/08/2015 09:19:43 »
I came across this thread https://www.quora.com/What-does-it-mean-to-say-a-wave-function-collapses at the Quora forum. The first person on the list writes: When people say that "the wavefunction collapses", that means that they don't understand how quantum mechanics works.  Frankly I find comments like that not only rude but ignorant and the person who says it being arrogant. Most textbooks speak of the collapse of the wave function.

To be clear on what it means see: Wave function collapse at
https://en.wikipedia.org/wiki/Wave_function_collapse
Quote
In quantum mechanics, wave function collapse is said to occur when a wave function—initially in a superposition of several eigenstates—appears to reduce to a single eigenstate (by "observation"). It is the essence of measurement in quantum mechanics and connects the wave function with classical observables like position and momentum.
I personally think that a wave is only a wave when it interacts, like a calm lake not interacting with the wind, or a pebble thrown in making a ripple.  ''a milk pond'' space.
added-light travels a linearity, if it waved one direction there is no force to make it curve back.it would go ''round in circles'',


..................................................................


if this line started to curve, it would orbit itself with no external altering force making it wave back

''Newton's first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force.''

a wave has a change of velocity
« Last Edit: 08/08/2015 10:14:33 by Thebox »
 

Offline Bill S

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Re: What do you think about the wave function collapse?
« Reply #2 on: 08/08/2015 13:28:49 »
I have not had time to follow the link yet; but is this a question of semantics?  For some time I’ve had the impression that “decoherence” is replacing “wave function collapse”, possibly as part of an attempt to remove the concept of conscious observer input.

The reasoning seems to go something like this: Instead of arguing that the intervention of a conscious observer causes the wave function of a quon to collapse; the interaction of the quon with its environment brings about decoherence.  Typically, this involves interaction with other quons and brings about a situation similar to the older idea of a collapsing wave function.  No conscious observer is necessary for this.
 

Offline Colin2B

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Re: What do you think about the wave function collapse?
« Reply #3 on: 08/08/2015 15:15:43 »
....Typically, this involves interaction with other quons and brings about a situation similar to the older idea of a collapsing wave function.  No conscious observer is necessary for this.
Bill, the term observation means it interacts with something else, it does not imply a conscious observer.
 

Offline Mordeth

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Re: What do you think about the wave function collapse?
« Reply #4 on: 08/08/2015 21:27:07 »
Wrong.  Measurements imply interactions.  But interactions, in quantum mechanics, do not necessarily imply measurements.  The terms are not interchangeable. The "collapse" is simply a measurement and in the Copenhagen interpretation is triggered by the observer or the measuring device connected to the observer.  Therefore, the measurement determines the state and the state is what was measured.  Yes fun fun! 

Anyone think that the measurement process and wave collapse are instantaneous and non-local?  If so, then information has been sent faster than light and the principle of locality has been violated.  Unless you have some hidden variables up your quantum sleeve.
 

Offline lightarrow

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Re: What do you think about the wave function collapse?
« Reply #5 on: 09/08/2015 12:29:41 »
I came across this thread https://www.quora.com/What-does-it-mean-to-say-a-wave-function-collapses at the Quora forum. The first person on the list writes: When people say that "the wavefunction collapses", that means that they don't understand how quantum mechanics works.  Frankly I find comments like that not only rude but ignorant and the person who says it being arrogant. Most textbooks speak of the collapse of the wave function.

To be clear on what it means see: Wave function collapse at
https://en.wikipedia.org/wiki/Wave_function_collapse
Quote
In quantum mechanics, wave function collapse is said to occur when a wave function—initially in a superposition of several eigenstates—appears to reduce to a single eigenstate (by "observation"). It is the essence of measurement in quantum mechanics and connects the wave function with classical observables like position and momentum.
It's one of th QM postulates, so I don't know how we could do without it, at least in the standard Copenhagen interpretation.

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« Last Edit: 09/08/2015 13:17:20 by lightarrow »
 

Offline PmbPhy

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Re: What do you think about the wave function collapse?
« Reply #6 on: 09/08/2015 21:44:45 »
Quote from: Bill S
I have not had time to follow the link yet; but is this a question of semantics?
Nope. It's a simple straightforward question. 

Quote from: Bill S
The reasoning seems to go something like this: Instead of arguing that the intervention of a conscious observer causes the wave function of a quon to collapse;...
What's a quon? Do you mean "Quon = quantum entity" as Nick Herbert defined it in his book "Quantum Reality"? If so then it's a very bad idea to use that term in a forum. He's the only person to use that term  and only in that text. So there's no reason to expect others to understand it. It will only go on to create confusion.
« Last Edit: 09/08/2015 21:49:54 by PmbPhy »
 

Offline Bill S

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Re: What do you think about the wave function collapse?
« Reply #7 on: 10/08/2015 14:40:25 »
Quote from: Pete
What's a quon? Do you mean "Quon = quantum entity" as Nick Herbert defined it in his book "Quantum Reality"? If so then it's a very bad idea to use that term in a forum. He's the only person to use that term  and only in that text. So there's no reason to expect others to understand it. It will only go on to create confusion.

Yes, that is the sense in which I use "quon".  The first time I used it in this forum I qualified it as "sensu Herbert" and gave the link to the Wiki reference.  I am not the only one to use the term in this forum, so it seems a little OTT to qualify/explain it on every use.  How dull our language would be if no one allowed new words/usage to enter it.  Imagine trying to conduct a modern physics discussion in Chaucerian English. :)
 

Offline sciconoclast

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Re: What do you think about the wave function collapse?
« Reply #8 on: 11/08/2015 13:19:15 »
Phrases like "wave function collapse" appear frequently in the vernacular. I often use phrases like this for expediency; but, they are technically incorrect. In quantum theory the so called wave function is not describing an actual wave. There is no wave. And nothing collapses. 

In the Bohr interpretation the function only describes what characteristics are possible for a photon. When the photon finally actualizes it has only one set of characteristics such as only one of many possible positions and one of many types of possible spin type ( I realize this is an over simplification ). The actualization of the photon then renders the function unnecessary at that point and this is sometimes referred to as the function collapse ( actually there is a new more limited function that then applies )

"Wave particle duality" is another common but incorrect phrase. Bohr used something like the convergence of time distance intervals along vector lines to calculated the points for the greatest probability for photon occurrence. This is completely different than the historic calculations of crest to crest increase in amplitude for photon occurrence used in wave functions. His function is only referred to as a wave function out of the historical preference.     

However, the predictions for the behavior of light are for the most part the same with both methods. That is why those working in optics and even photonics tend to use the simpler wave functions. For example two nice old gentlemen shared a Nobel prize for applying the math of quantum theory to the Hanbury, Brown and Twist effect but the astronomers working with that multiple source interferometry still use the historic wave functions. 

Unlike Bohr, who believed that the photon characteristics were not determined until a later interaction, Einstein believed that the characteristics were initially determined. The debate continues and the pendulum that first swung towards the Bohr interpretation seems to me to be starting to swing back towards Einstein's views. This would make all of of mentioned concepts irrelevant. 
 

Offline lightarrow

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Re: What do you think about the wave function collapse?
« Reply #9 on: 11/08/2015 16:26:25 »
Phrases like "wave function collapse" appear frequently in the vernacular. I often use phrases like this for expediency; but, they are technically incorrect. In quantum theory the so called wave function is not describing an actual wave. There is no wave. And nothing collapses. 
I prefer "reduction of state" but what counts is the exact mathematical and physical meaning; witout this one, every term is meaningless. The problem, in case, is if there is something physical which changes in the quantum system which is being measured. This is still a matter of discussion.
Quote
In the Bohr interpretation the function only describes what characteristics are possible for a photon.
You have chosen a bad example because it's not yet established if a photon has a wave function or not and in case which is it.

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« Last Edit: 11/08/2015 16:31:42 by lightarrow »
 

Offline sciconoclast

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Re: What do you think about the wave function collapse?
« Reply #10 on: 11/08/2015 23:46:31 »
"Bohr never talked about the collapse of the wave packet. Nor did it make sense for him to do so because this would mean that one must understand the wave function as referring to something physically real."
http://plato.stanford.edu/entries/qm-copenhagen/#MisCom
 

Offline PmbPhy

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Re: What do you think about the wave function collapse?
« Reply #11 on: 12/08/2015 03:11:29 »
Quote from: sciconoclast
"Bohr never talked about the collapse of the wave packet. Nor did it make sense for him to do so because this would mean that one must understand the wave function as referring to something physically real."
http://plato.stanford.edu/entries/qm-copenhagen/#MisCom
That's not true at all. The wave function is and always has been understood to be a mathematical tool. The collapse of the wave function is also merely a way of describing the vanishing of all eigenfunctions in the expansion of the wave function. Recall the quote in the opening post (OP). Have you actually read that website that I referenced in the OP? If not then I recommend doing so. It's a very simple idea in fact. Suppose an observable has a discrete spectrum. Then the wave function can be expressed as

|Psi> = a1|psi1> + a1|psi1> + a1|psi1> + .... + an|psin>

As Wiki's words - When an external agency (an observer, experimenter) measures the observable associated with the eigenbasis |phii>, the wave function collapses from the full |psi> to just one of the basis eigenstates, |phii>. That is

|Psi> ---> |psii>

That's all there is to it, i.e. its merely a way to describe what's going on and it's correct by definition.
 

Offline sciconoclast

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Re: What do you think about the wave function collapse?
« Reply #12 on: 12/08/2015 14:51:30 »
You need to read my post more carefully. The quote is stating that the wave function is a mathematical tool and not a physical entity.

I f you disagree with the part about Bohr never using the term collapse and it not being part of his original quantum theory; then you are in disagreement with the credentialed sources at Stanford University that were quoted.

There has been a recent hypothesis that has surfaced in which light exist as a superimposition of both the particle and wave states until tested for as one of those possibilities. I believe that this is what you guys are reading. This is not orthodox theory and is far from achieving theory status. In its attempt to answer some new observations it has created more problems than solving them. Although I am always for new theories and it may develop into something. 
 

Offline PmbPhy

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Re: What do you think about the wave function collapse?
« Reply #13 on: 12/08/2015 16:02:22 »
Quote from: sciconoclast
You need to read my post more carefully.
I really wish people would stop using that comment as a canned response when someone disagrees with them. I already READ your post carefully.

Quote from: sciconoclast
The quote is stating that the wave function is a mathematical tool and not a physical entity.
Totally wrong. There is nothing in the snippet that you quoted that indicates that they're talking about the wave function is a mathematical tool. However since I know quantum mechanics and I know that site I know that it's a given. The part I disagree with is the part that says
Quote
... this would mean that one must understand the wave function as referring to something physically real.
because it means no such thing and doesn't imply it either.

Quote from: sciconoclast
I f you disagree with the part about Bohr never using the term collapse..
How on Earth did you arrive at that conclusion based on what I posted? I said neither said nor meant no such thing.

Quote from: sciconoclast
There has been a recent hypothesis that has surfaced in which light exist as a superimposition of both the particle and wave states until tested for as one of those possibilities.
That's hardly recent. It's been part of quantum mechanics from the beginning. It's called the wave-particle duality. It appeared in its first form in de Broglie's PhD thesis in 1924.

Quote from: sciconoclast
I believe that this is what you guys are reading. This is not orthodox theory and is far from achieving theory status. In its attempt to answer some new observations it has created more problems than solving them. Although I am always for new theories and it may develop into something.
You sure have a lot to learn about quantum mechanics my friend. A hell of a lot.
 

Offline sciconoclast

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Re: What do you think about the wave function collapse?
« Reply #14 on: 13/08/2015 03:06:01 »
" that would mean that one must understand the wave function as referring to something physically real" is taken out of context. You need to place " Nor did it make sense for him to do so because it would mean " in front of it. You need to read more carefully. Actually, Faye's phrasing might be confusing if English is not someones first language. A simple translation or paraphrasing would be: Bohr would never use the term collapse because it would mean he was talking about something physical which he did not believe was physical.

I am well aware of DeBroglie's work. There are a lot of versions of quantum theory and when I see a simple question that I think I can answer I feel obligated to do so with the most accepted view, even if it is not my own, unless I am in the new theories section. At a recent conference a pol was taken and the attending physicist overwhelmingly selected the Bohr interpretation. DeBroglies wave particle duality is in direct opposition to Bohr"s principle of non-complementarity.

Several years ago I was posting some original tertiary experiments on this forum that favored the Bohm DeBroglie interpretation over the Bohr interpretation. I was looking for some feed back before making a fool of myself elsewhere. After JP informed me that this was not an appropriate site for this I stopped doing it. Sense then with the help of a fellow retired engineer and good friend I have gone on to do some more elaborate and sensitive versions which are currently under review. If you want to play around and have some fun there is an hour long video on my youtube channel that demonstrates a lot of simple experiments you can easily do at home that challenge the Bohr interpretation and support the Bohm DeBroglie interpretation. So I am well aware of the Bohm Debroglie interpretation. I do not think that these guys would have ever used the term collapse or superposition as they believed they were dealing with a real physical entity, at least not in the joint interpretation that they published.

You can find a version of quantum theory to support just about any claim you want to make. For example Heisenburg who was part of the Copenhagen school along with Bohr disagreed with Bohr in that he thought the functions were describing something real and may have used the term collapse. 

You are right I have a lot to learn about quantum theory and I am discovering something new very regularly.     
 

Offline lightarrow

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Re: What do you think about the wave function collapse?
« Reply #15 on: 13/08/2015 08:01:06 »
You need to read my post more carefully. The quote is stating that the wave function is a mathematical tool and not a physical entity.
I f you disagree with the part about Bohr never using the term collapse and it not being part of his original quantum theory; then you are in disagreement with the credentialed sources at Stanford University that were quoted.
Don't know if when you talk about Bohr ideas on collapse you also want to mean "Copenhagen interpretation and formulation of QM", however I have to inform you that the collapse is part of standard QM formulation fron 1932, with the work of Dirac and Von Neumann and his book "Mathematical Foundations of Quantum Mechanics":
https://en.wikipedia.org/wiki/Mathematical_Foundations_of_Quantum_Mechanics.

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Offline PmbPhy

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Re: What do you think about the wave function collapse?
« Reply #16 on: 13/08/2015 09:19:42 »
Quote from: sciconoclast39431561
You need to read more carefully.
You're getting to be really irritating by claiming that I "You need to read more carefully" and crap like that. I know EXACTLY what I read and what it said and meant. Claiming that I didn't read it carefully is utter crap. All you've done is make a false accusation by implying that what I said was wrong when in fact I know the reasons for precisely what I said and why I said it. So please cut the crap.

Quote from: sciconoclast39431561
A simple translation or paraphrasing would be: Bohr would never use the term collapse because it would mean he was talking about something physical which he did not believe was physical.
What the hell is wrong with you anyway? I KNOW that's what the article said for cripes sake. Why do you keep dwelling on that useless and irrelevant point? Nobody cares about it except you! Whether Bohr would or wouldn't use it is irrelevant to me. The FACT of the matter is that it has a well-defined meaning and the phrase is found in most texts on quantum mechanics including ones used in graduate school.

Quote from: sciconoclast39431561
There are a lot of versions of quantum theory and when I see a simple question that I think I can answer I feel obligated to do so with the most accepted view, ..
And you already did so in reply #8 and in that post it was very clear that you don't understand quantum mechanics very well so after I read that nothing you said was of any value to me.

For that reason and your continued rude remarks claiming that I need to read more carefully when in fact the problem is that you're totally clueless, I will never respond to another post made by you on this discussion board. You're just too rude and ignorant to want to deal with.
 

Offline PmbPhy

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Re: What do you think about the wave function collapse?
« Reply #17 on: 13/08/2015 09:22:37 »
Quote from: lightarrow
Don't know if when you talk about Bohr ideas on collapse you also want to mean "Copenhagen interpretation and formulation of QM", however I have to inform you that the collapse is part of standard QM formulation fron 1932, with the work of Dirac and Von Neumann and his book "Mathematical Foundations of Quantum Mechanics":
https://en.wikipedia.org/wiki/Mathematical_Foundations_of_Quantum_Mechanics.
Don't bother with him. He has no idea what the concept means. From his statement above that
Quote
they are technically incorrect. In quantum theory the so called wave function is not describing an actual wave. There is no wave. And nothing collapses. 
it's clear that he doesn't know that the wave function collapse is a mathematical statement. That's one of the reasons I said he's clueless.
It's also clear that he doesn't even know that the wave-equation describes the wave behavior of matter such as the wave properties of electrons in a nickel crystal lattice.
« Last Edit: 13/08/2015 09:24:36 by PmbPhy »
 

Offline sciconoclast

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Re: What do you think about the wave function collapse?
« Reply #18 on: 13/08/2015 15:21:17 »
There are articles that have appeared recently with titles such as "Quantum Physics just got Easier to Understand" http://www.huffington.com/2014/12/24  . It is obvious from these titles that a new hypothesis is being presented. Sense a lot of Pmbphy and Lihhtarrows comments could be taken as verbatim to what was in these articles I assumed that this is what they were really presenting. If this was incorrect then I apologize for that assumption. On the other hand if that is what they are up to then I would welcome a rational discussion about the experiments that have been said to support that view.

I do not think that I insulted anybody. Stating that you think someone has taken something out of context is not an insult if you believe it to be true. I am trying to conduct a civil and rational conversation and have introduced references for the most important points. It is unfortunate that these guys are no longer interested in my post but there are probably other viewers that are, or perhaps not. It really doesn't matter that much.

 

Offline Bill S

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Re: What do you think about the wave function collapse?
« Reply #19 on: 13/08/2015 20:33:37 »
Quote
http://www.huffington.com/2014/12/24

I tried following this link and all I got was a blank page.  Is that some kind of comment?   ???
 

Offline sciconoclast

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Re: What do you think about the wave function collapse?
« Reply #20 on: 13/08/2015 21:08:12 »
Opps, sorry. The link should be http://www.huffingtonpost.com/2014/12/24/       

If that doesn't work just google the title.
 

Offline PmbPhy

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Re: What do you think about the wave function collapse?
« Reply #21 on: 14/08/2015 03:01:37 »
Quote from: sciconoclast
I do not think that I insulted anybody.
Alright then. My fault. I'll accept that perhaps it wasn't an insult, that it's merely very irritating. You keep claiming that I misread something when in actuality it's the furthest thing from the truth. For example; in reply #10 you quoted this
Quote
Bohr never talked about the collapse of the wave packet. Nor did it make sense for him to do so because this would mean that one must understand the wave function as referring to something physically real.
I explained that That's not true at all. The wave function is and always has been understood to be a mathematical tool. Then you responded by saying You need to read my post more carefully. The quote is stating that the wave function is a mathematical tool and not a physical entity. which is wrong! The post says "Nor did it make sense for him to do.." their reason being that if one spoke of the "collapse of the wave packet" that it "would mean that one must understand the wave function as referring to something physically real."
 where in truth it one does not have to understand the wave function as being physically real. So you see, it was you who didn't understand what you were quoting because you didn't pay close enough attention to what you were reading.

Then you wrote
Quote
A simple translation or paraphrasing would be: Bohr would never use the term collapse because it would mean he was talking about something physical which he did not believe was physical.
Obviously. And that's what I explained was a wrong belief on Bohr's part, i.e. that assertion "it would mean" is totally wrong since it does not mean that and that's what I said in reply #11. If you actually thought that "The quote is stating that the wave function is a mathematical tool and not a physical entity." then you contradicted yourself with what I just quoted.

As I said, you keep claiming that I need to read more carefully when in fact I'm right on and it's you who aren't paying attention.

And since you keep doing this and your confused and your knowledge of qm is quite lacking I'm tired of trying to set you straight since you're not listening. This isn't an insult, merely an honest observation. You clearly don't understand know that there actually IS a wave being described by the Schrodinger equation. Those waves are complex functions. They have the property of interference as demonstrated when electrons are diffracted by a nickel crystal lattice. After all that's part of the wave-particle duality. The wave itself is not observable just the probability density and whatever that shows. There may in fact be a propagating pulse whose width increases with time etc. What is observable is the probability density and in that distribution the wave nature becomes manifest.

So as I said, I've had enough of your poor understanding and confused claims.
« Last Edit: 14/08/2015 18:31:30 by PmbPhy »
 

Offline PmbPhy

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Re: What do you think about the wave function collapse?
« Reply #22 on: 14/08/2015 18:16:19 »
sciconoclast - I never got around to commenting on the following claim
Quote from: sciconoclast
"Wave particle duality" is another common but incorrect phrase.
Assertions like this is why I said you have a very poor understanding of quantum mechanics. The wave-particle duality is a fact and the term "wave-particle duality" for the phenomena is a perfect way to express this fact. All quantum mechanics textbooks either use the term outright or they discuss the subject of the wave-particle duality in detail, such as in Young's double slit experiment.

To start your education on the wave-particle duality I recommend starting here: http://physics.weber.edu/carroll/honors-time/duality.htm   E.g. see the part that says
Quote
    The implications of this (which are described in Chapter 6 of Richard Feynman's The Character of Physical Law) are staggering.
In that book Feynman wrote on page 128
Quote
This growing confusion was resolved in 1925 or 1926 with the advent of the correct equations for quantum mechanics. Now we know how the electrons and light behave. But what do we call it? If I say they behave like particles I give the wrong impression; also if I say they behave like waves. They behave in their own inimitable way, which technically could be called the quantum mechanical way. They have in a way that is nothing like you have ever seen before. Your experience is incomplete. The behavior of things on a very tiny scale is simply different. An atom does not behave like a weight hanging n a spring and oscillating. Nor does it behave like a miniature representation of the solar system with planets going around in orbits. Nor does it appear to be like a cloud or a fog of some sort surrounding the nucleus. It behaves like nothing you have ever seen before.
   There is one simplification at least. Electrons behave in this respect in exactly the same way as photons; they are both screwy, but in exactly the same way.
That, in essence, is the wave-particle duality! Please learn it - correctly.

It's rare not to see a quantum mechanics textbook use the term. Even those who don't use it explain the concept since it's the central idea of quantum mechanics.

See: https://en.wikipedia.org/wiki/Wave%E2%80%93particle_duality
Quote
Wave–particle duality is the fact that every elementary particle or quantic entity exhibits the properties of not only particles, but also waves.

Here are some perfect examples from the quantum mechanics literature where the phrase is used. The following are very well known graduate level texts;

Quantum Mechanics - 3rd. Ed. by Eugen Merzbacher, page 2. After describing the dual nature of matter he wrote
Quote
Louis de Broglie proposed that the wave-particle duality is not a monopoly of light but is a universal characteristic of nature which becomes evident when the magnitude of h cannot be neglected. He thus brought out a second fundamental fact, usually referred to as the wave nature of matter.

Chapter 3 ofIntroduction to Quantum Physics by A.P. French and Edwin F. Taylor, is entitled Wave-particle duality and bound states. So the entire chapter is about something that you claim is wrong. Both of these authors are extremely good physicists and authors of physics. Both either teach or taught at MIT at one time or another. So you are guaranteed that they know the subject a hell of lot better than anybody on this discussion board. If you want to you can download that text and read that chapter from here: http://bookos-z1.org/book/2316071/f921a2  You have to first register with the site and then login. Registration is free. It's a great place to download almost any text textbook that you want from!

When I was searching for this I came across an entire chapter on the collapse of the wavefunction. You can find it in Quantum Mechanics; The Theoretical Minimum by Leonard Susskind and Art Friedman. I.e.
Quote
4.14 Collapse
....
But something different happens when an observation is made. An experiment to measure L will have an unpredictable outcome, but after the measurement is made, the system is left in an eigenstate of L. Which Eigenstate? The one corresponding to the outcome of the measurement. But this is unpredictable. So it follows that during an experiment the state of a system jumps unpredictably to an eigenstate of the observable that was measured. This phenomena is called the collapse of the wave function.
Do you get it now? All that "collapse of the wave function" means is is a description of the above described phenomena, period!

Back to wave-particle duality. Section 2 of Quantum Mechanics by Cohen-Tannoudji, Diu and Laloe is entitled Wave-particle duality. You can download this from http://bookos-z1.org/book/999673/966ae4 This is a graduate level QM text. In fact its the text I myself used in graduate school.

Another graduate QM text that uses it is Principles of Quantum Mechanics - 2nd Ed. by R. Shankar, page 113.

Quote from: sciconoclast
Bohr used something like the convergence of time distance intervals along vector lines to calculated the points for the greatest probability for photon occurrence. This is completely different than the historic calculations of crest to crest increase in amplitude for photon occurrence used in wave functions. His function is only referred to as a wave function out of the historical preference. 
Totally irrelevant. I fail to see why you keep bring up Bohr because what he said is of no consequence to the subject matter. That you think it does is just another example of why you need a much better education in physics. Again, no insult intended. Just an honest observation and some good advice. But if you're not honest with us or yourself you'll never be able to learn the correct physics.   

Example; You keep on thinking that "wave function" is some sort of historical accident or historical remnant. That's about as wrong as you'll ever get in quantum mechanics and tells me that you've never even read a good quantum mechanics textbook such as that of Griffiths or French and Taylor!
« Last Edit: 14/08/2015 19:03:43 by PmbPhy »
 

Offline sciconoclast

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Re: What do you think about the wave function collapse?
« Reply #23 on: 15/08/2015 02:31:17 »
Maybe we have a communication problem and it might be my fault.

I think that the best way to get my view across is to use something I am very familiar with such as the double slit experiment as an example.

Prior to Einstein and Compton the interference pattern was generally thought to be a real physical wave in the physical aether. The wave passing through both slits and the subsequent multiple waves interfering to produce visible light at the points of greatest amplitude.

The prevailing quantum theory is that the photons do not come into existence, or actualize as photons, until they actually encounter the detector. In this theory nothing physical, photon or wave, is propagating through space and passing through the slits. Where the possible paths, at the same time distance interval, converge at the detector is where the greatest probability for photon actualization occurs.

These intersections are calculated by calculating the actual possible trigonometric paths along with some other criteria. Both methods produce the same resulting pattern at the target. I would much rather use the simpler wave function with the slit spacing, the distance to the detector, and the frequency, to verify an interference pattern than the more complicated Bohr method. So does everybody else except the quantum purist in a very special application.

At the detector, when the photon actualizes, it is usually said that the wave function has collapsed. There are other terms that are sometimes used, such as collapse of the quantum probability field.

There are many possible future manifestations for a quantum entity ( despite the objections by Schrodinger's kitty cat ) and there are many ways to calculate those possibilities and the wave function is only one. These functions are only used to calculate probabilities not to describe physical occurrences.

There is a school of thought that the wave function is actually describing a physical wave, sometimes referred to as the psi-ontic school, and one that does not psi-epirtemic. As far as I know the view that it is not a physical wave is the prevailing one. I personally believe that there is a real physical wave component and if that is the prevailing view then I have been wasting a lot of time trying to prove it.     

Here are some quotes you might get a laugh out of. "When we teach quantum mechanics to undergraduate physics majors, we generally give them a list of postulates that go something like this. 1. Quantum states are represented by wave functions, which are vectors in a mathematical space called Herbert space...... Of course we can do better, since textbook quantum mechanics is an embarrassment."  www.preposterousuniverse.com/blog/2014/07/24/why-probability-in-quantum-mechanics-is-given-by-the-wave-function-squared/

"One of the main reasons why the wave function in current quantum physics has to be considered fictional is because it is expressed by the resultant of many sub-wave functions representing probabilities or attributes of entities of the natural world in the form of respective orthogonals."   www.bibliotecapleyades.net/cienia/secret_projects/project419.htm

If you think that there is a physical wave component to light I would be in agreement. If you think that this is the prevailing theory or that there is an actual physical collapse I would not. But I am only expressing an opinion.   

Of course a lot depends on your view of reality. Some think that mathematical formulas are reality.   
 

Offline sciconoclast

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Re: What do you think about the wave function collapse?
« Reply #24 on: 15/08/2015 11:46:12 »
Oops: Finally got it. You were not objecting to the wave function as being a mathematical abstraction but to saying that using the term function collapse means that it is not. I guess I am the one who should read more carefully.

If you consider the wave function as only a tool for prediction then you are in agreement with prevailing theory. Keeping with the tool analogy the function collapse would only mean laying down one tool and picking up a different one.

Of course as you know I favor the Bohm DeBroglie type of model in which a photon core exist from the onset and generates a broader actual wave. There is no function collapse in this model but I am the one who is outside of prevailing theory.

Please accept my apology for miss-reading you if that is the case,
 

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Re: What do you think about the wave function collapse?
« Reply #24 on: 15/08/2015 11:46:12 »

 

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