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Interpretations of Quantum Mechanics (is there a general consensus?) 
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#1
Feb412, 02:59 AM

P: 30

Hi :)
I recently read a book that states that most scientists believe the wave function represents a real field (i.e., one that possesses energy and momentum). I think this is part of the transactional interpretation of QM but not sure... can anyone confirm whether the book I read is right about this or not? 


#2
Feb412, 05:16 AM

P: 353

I don't know what most scientists believe, but I find that statement strange. I would have thought that the one thing, about the wave function, they would agree on, is that it doesn't represent a real field.



#3
Feb412, 06:29 AM

P: 2,179

From my experience, I would say there is not a general consensus on this point, and most scientists seem to take the view of SUAC  Shut Up And Calculate  which means they know how to do the calculations and just don't worry too much about the interpretation.



#4
Feb412, 07:38 AM

P: 476

Interpretations of Quantum Mechanics (is there a general consensus?)



#6
Feb412, 10:51 AM

PF Gold
P: 3,080

Not only don't I think there's a consensus on that, I'm not even sure what the statement means. A field is real if it carries energy and momentum? How does one know if a field carries energy and momentum? I would say that thinking is backward we don't ask if it carries energy and momentum, and then decide we think it's real, we ask if we think it's real, and then decide it carries the energy and momentum. In other words, we all know we wish to associate energy and momentum with the wavefunction, whether we regard it as real or not, so we first have to ask if we regard it is real before we can decide whether or not it "carries" that energy and momentum, instead of just "associates with" that energy and momentum. So the field is not real if it carries energy and momentum, the field carries energy and momentum if it is real.



#7
Feb412, 04:42 PM

P: 30

Yeah, what you said makes sense, Ken. I would have thought that most scientists don't believe the wave function is real, too, martin. I may have misstated the part about the wave function a bit, but here's a quote from the preface of the book:
"...if someone, not a theoretical physicist and not thoroughly acquainted with modern methods of analysis, were to attempt to digest a current article dealing with nuclear forces or cosmic rays, relying for help on the available books on the subject, he would discover to his dismay that modern quantum mechanics differs radically from that which he finds in the textbooks... More confusing to him is the interpretation of a field in the new mechanics. It seems evident that what is meant is a real field possessing energy and momentum. Yet the textbooks attach a purely symbolic meaning to the wave field of a particle, picturing the field concept merely as a probability function." ...and there you have it. 


#8
Feb412, 04:57 PM

P: 476




#9
Feb412, 05:28 PM

P: 30

hehe... Do you seriously think I should? :)



#10
Feb512, 03:58 AM

Sci Advisor
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P: 2,543

I personally don't believe it does  I think its like classical probability theory  its simply a device for calculating statistical outcomes. Check out: http://arxiv.org/pdf/quantph/0111068v1.pdf Thanks Bill 


#11
Feb512, 09:44 AM

Sci Advisor
P: 1,969

There is something about the wave function that makes a completely different kettle of fish than fields such as the electric field. That is, that unlike the electric field, the wave function is not a field in the physical world. It's a field in configuration space.
The distinction is this: In the case of an electric field, I can point to a particular spot, and ask "What is the value of the electric field right there?" You cannot ask the analogous question about the wave function, because it is not a probability amplitude on points in space. To see why not, consider a twoparticle wave function. In general, It would be written as (simplifying to the case of 1 spatial dimension): ψ(x_{1}, x_{2}), the square of which gives the probability density of finding the first particle at position x_{1} and the second particle at position x_{2}. It doesn't make any sense for me to point to a particular point and ask what the value of the wave function is at that point. I don't know what the implications of this physicalspace versus configuration space distinction is for whether the wave function is "real", but it certainly shows that the wave function cannot be considered an ordinary field like the electric field. 


#12
Feb512, 11:45 AM

PF Gold
P: 3,080

Yet you can point to a box in real space and ask "what is the probability of finding a particle in that box", even for multipleparticle wave functions (if the particles are distinguishable, you can also specify which type of particle you are asking about). You can also ask about correlations like "what is the probability of finding particles in both of these two boxes", and so on. So it's a more sophisticated kind of field, but it seems to me one can still imagine it "exists" in real space if one wants to. True, it is kind of a "question answering field", but then, so are they all. Does one want to attribute independent existence to questionanswering fields? No less so in quantum than classical physics, it was always something of a stretch in my view!



#13
Feb512, 11:59 AM

P: 353

@ Ken_G: The point of stevendaryl is that fields are represented by mathematical object that have domain spacetime not configuration space. I thought this was so obvious, that's why I didn't even say in my post!



#14
Feb512, 12:43 PM

Sci Advisor
P: 1,969

Yet you can point to a box in real space and ask "what is the probability of finding a particle in that box", even for multipleparticle wave functions (if the particles are distinguishable, you can also specify which type of particle you are asking about). You can also ask about correlations like "what is the probability of finding particles in both of these two boxes", and so on. So it's a more sophisticated kind of field, but it seems to me one can still imagine it "exists" in real space if one wants to. True, it is kind of a "question answering field", but then, so are they all. Does one want to attribute independent existence to questionanswering fields? No less so in quantum than classical physics, it was always something of a stretch in my view!Well, I don't think there was ever any question about whether the wave function was useful for answering questions. It certainly provides information about the real world. My point is that it isn't something that resides in the real world. It isn't an object that exists in some location, nor is it a field that varies from location to location. 


#15
Feb1212, 09:30 AM

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P: 677

I really like Matt Leifer's suggestion in this post:
http://mattleifer.info/2011/11/20/ca...statistically/ 


#16
Feb1212, 11:16 AM

P: 8

GellMann once wrote, ‘Bohr brainwashed a whole generation of physicists into ‘believing' the Copenhagen interpretation of quantum mechanics'.



#17
Feb1212, 01:29 PM

P: 66

So a wave function is not a wave and its not a particle, its an entity of some sort in 'superposition' that spreads out in x,y,z and t. We can only find out if its 'there' by decohering it. Otherwise it is not a physical, real entity.
It behaves as though it were a 'calculation' waiting for its result (at some x,y,z and t) on decoherence. It leaves no track of its path. It simply 'arrives'. We know where it came from but have no idea of its path to its destination. So what entity can achieve this? Something superposition is not a 'thing'  its not an object that we cannot enclose or put in a container  unless we decohere. And even then decoherence results in 'values observed'. 


#18
Feb1212, 02:38 PM

P: 8

We can't detect gravitational waves right now, but it does not mean they do not exist. It just mean our instruments are not sensitive enough to detect them directly right now. 


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