Classical Atom Models: A Nobel Prize Waiting to be Won?

[ZapperZ]

I didn't know anything about superconductivity until I read this post (and then was motivated to read up a bit on it). Thanks for the link to Mead's paper, which I've read and will reread.
Anyway, I was just asking a question in my post. I don't know quantum theory well enough to think that it should (or if it can) be changed, and I don't know the details of all the various experimental quantum phenomena well enough to have any good idea whether or not there's any reason to think that they might all be explained classically or semi-classically or whatever (although I've read some papers on this in the course of plodding through my quantum theory text).
Now, at the risk of sounding super ignorant, what is it that makes the superconductivity phenomenon a uniquely quantum phenomenon with, as you seem to indicate, no hope of ever being described in a classically visualizable way?

I know I have mentioned this before, maybe even in this thread, and Carver Mead also have said the same thing. Phase coherence is something that classical mechanics does not have in describing the dynamics of a system. For a gazillion particles to be in a long-range phase coherence, this has no classical counterpart. And then, when you add to the fact that the phase of the order parameter can produce a spontaneous supercurrent around a loop, that has also no equivalent phenomenon in classical physics. Refer to the Van Harlingen paper.

These are only 2 of a numerous set of examples from superconductivity/superfluidity. The physics gets more complex as one considers the exotic observations from high-Tc superconductors.

Zz.

 

[QMrocks]

I know I have mentioned this before, maybe even in this thread, and Carver Mead also have said the same thing. Phase coherence is something that classical mechanics does not have in describing the dynamics of a system. For a gazillion particles to be in a long-range phase coherence, this has no classical counterpart. And then, when you add to the fact that the phase of the order parameter can produce a spontaneous supercurrent around a loop, that has also no equivalent phenomenon in classical physics. Refer to the Van Harlingen paper.
These are only 2 of a numerous set of examples from superconductivity/superfluidity. The physics gets more complex as one considers the exotic observations from high-Tc superconductors.
Zz.

Looks like i got to read a module on superconductor next semester to really appreciate. If you dun mind, pls give me some excellent textbooks on superconductors.

 

[ZapperZ]

Looks like i got to read a module on superconductor next semester to really appreciate. If you dun mind, pls give me some excellent textbooks on superconductors.

I first had a formal introduction to the theory of Superconductivity using Michael Tinkham's book "Introduction to Superconductivity". I think many people in the community are very familiar with this text. Bob Schreifer's (the "S" in BCS) text on the theory of superconductivity is also highly recommended because he covered the field theoretic method of BCS theory, something that Tinkham did not go over in detail.

Zz.

 

[QMrocks]

I first had a formal introduction to the theory of Superconductivity using Michael Tinkham's book "Introduction to Superconductivity". I think many people in the community are very familiar with this text. Bob Schreifer's (the "S" in BCS) text on the theory of superconductivity is also highly recommended because he covered the field theoretic method of BCS theory, something that Tinkham did not go over in detail.
Zz.

Great! i love Dover books (and i happen to have Michael Tinkham's Group theory book too). Will check out on these two books. Thanks for the tip again!

 

[RandallB]

You CAN describe the double slit using classical optics, ……..

No you can’t

Here's the deal. The MORE you have to produce "single" of any object ...

Well duh, these experiments don’t mean anything in CM vs. QM unless they are run in a one particle at a time manner. But the data is still collected to be evaluated MACROSCOPICALLY to learn about the microscopic. To allow otherwise for CM would be like CM running superconductivity tests at room temp it wouldn’t make any sense.

Superconductivity and superfludity are QM phenomena at the MACROSCOPIC level. That is what's so astounding about these things.
Eh?

Eh what? All these things are astounding; the point of QM is no direct measurement or explanation can be made at the microscopic level. Only macroscopic collections of data that can be evaluated with HUP in mind.

So again these all seem to be difficult (if not impossible) obstacles for CM to get by.
Why is your personal favorite any more ‘impossible’ or important than the others that CM should ignore those others and focus on yours?

 

[QMrocks]

sorry to intercept.. but..

No you can’t

Do you mean that if i perform a numerical simulation of Maxwell equation on a double slit setup, i will not be able to reproduce the interference effects?

Why is your personal favorite any more ‘impossible’ or important than the others that CM should ignore those others and focus on yours?

Either u or me are imagining things... but i remember Zapper said it differently. He asked why there's still no CM explanation of superconductivity. So it seems that people are ignoring Superconductivity and not the other way.. What is your opinion on this? Do you think there's any possibility that CM can account for Superconductivity?

 

[Careful]

sorry to intercept.. but..
Do you mean that if i perform a numerical simulation of Maxwell equation on a double slit setup, i will not be able to reproduce the interference effects?
Either u or me are imagining things... but i remember Zapper said it differently. He asked why there's still no CM explanation of superconductivity. So it seems that people are ignoring Superconductivity and not the other way.. What is your opinion on this? Do you think there's any possibility that CM can account for Superconductivity?

I do not know about superconductivity, but I know for sure that (at least some part of) the quantum Hall effect (another macroscopic ``quantum´´ effect) has been explained by classical physics using particles of fractional charge. I again have to agree with Vanesch here (it is getting boring that I have to agree with him, apart from consciousness of course ) that the real test for classical versus quantum is at the level of simple systems where we can *exactly* compute everything (say the energy levels of helium, the angular momentum quantum numbers etc.). The answer as to why CM is running behind is a retorical question which has been answered already. Vanesch, can you change your name into Schevan, Scevnah or Hasnvec ?

 

[QMrocks]

I do not know about superconductivity, but I know for sure that (at least some part of) the quantum Hall effect (another macroscopic ``quantum´´ effect) has been explained by classical physics using particles of fractional charge. I again have to agree with Vanesch here (it is getting boring that I have to agree with him, apart from consciousness of course ) that the real test for classical versus quantum is at the level of simple systems where we can *exactly* compute everything (say the energy levels of helium, the angular momentum quantum numbers etc.). The answer as to why CM is running behind is a retorical question which has been answered already. Vanesch, can you change your name into Schevan, Scevnah or Hasnvec ?

i see... i supposed the SED approach is usually via numerical simulation, so that's why a large scale object like solid state system is too unfriendly..

 

[NateTG]

I was under the impression that the problem wasn't the double-slit experiment by itself, but that results of double-slit experiements and photo-electric experiments combine to cause problems:

Specifically - experiments with the photo-electric effect suggest that light is 'local' in the sense that it's energy is delivered in 'little packets' whose energy depends on the frequency of light, and that the intensity of light is determined by 'how many' of these packets there are.

Meanwhile, two-slot experiments suggest that light is non-local in the sense that 'information' about the light must go through both slots in order to explain the behavior.

Now the problem is that light is a phenomenon acting on two very different scales in these experiments: in one we're looking at atom-scale, and on the other, the other is at the wave-length of the light - this is many orders of magnitude difference.

My understanding is that in order to handle this disparity orthodox quantum mechanics suggests that 'measurement' causes 'wave-form collapse' which spontaneously, and temporarily changes a local phenomenon into a non-local one. Equivalently, one could postulate a noisy vacuum which provides virtual particles that simulate the non-local interaction, or we could have 'locally scrambled space' where wormholes are constantly popping into and out of existence.

 

[RandallB]

sorry to intercept.. but..
Do you mean that if i perform a numerical simulation of Maxwell equation on a double slit setup, i will not be able to reproduce the interference effects?

No interception at all, your in play here as well. That’s correct, not in a way that would explain it for an individual particle- an expanding wave packet would be superposition.

Either u or me are imagining things... but i remember Zapper said it differently. He asked why there's still no CM explanation of superconductivity. So it seems that people are ignoring Superconductivity and not the other way.. What is your opinion on this? Do you think there's any possibility that CM can account for Superconductivity?

Your right that's the way he said it. The point is so what if “there's still no CM explanation of superconductivity” unless he is satisfied with the arguments already given by CM on the others what difference could it make.

Yes it seems very likely to me that CM will be able account for Superconductivity. BUT only IF, When & after completely accounting for one or two paradoxes currently only resolved by superposition! Not just coming close but actually completely explain it.
Just because there are some “attempts” by CM that kind of come close is no reason to demand that QM must do the same for superconductivity, that’s just silly.

As Vanesch pointed out early on the key difference between QM & CM is superposition. If CM can show that that is wrong, then QM is done for.
So if CM is to assume superposition is invalid, that leaves several paradoxes unresolved. CM must prove it has not just a “better” solution, but a complete and real solution to at least one of the basics (entanglement, double slit, electron not crashing into protons, etc.)

The point of this thread as Vanesch kicked it off is where CM is now and what it needs to do. (Not who as an idea that should crush any CMer from even trying) Other than producing a solution a start could also be made on refuting the negative prove against CM where Bell says CM cannot work. I really don’t see how any “complete proof” can be considered complete if it doesn’t lead to that any way. Certainly for CM that should be more important than superconductivity, even if it can be developed into another form of a negative proof against CM.

As to who will win this “race” how can we tell till we know, till then I’ve never been much for giving odds, so I’ll take the odds and bet on CM.
RB

 

[ZapperZ]

No you can’tWell duh, these experiments don’t mean anything in CM vs. QM unless they are run in a one particle at a time manner. But the data is still collected to be evaluated MACROSCOPICALLY to learn about the microscopic. To allow otherwise for CM would be like CM running superconductivity tests at room temp it wouldn’t make any sense.Eh what? All these things are astounding; the point of QM is no direct measurement or explanation can be made at the microscopic level. Only macroscopic collections of data that can be evaluated with HUP in mind.
So again these all seem to be difficult (if not impossible) obstacles for CM to get by.
Why is your personal favorite any more ‘impossible’ or important than the others that CM should ignore those others and focus on yours?

Because, and read this again, superconductivity and superfluidity are the most OBVIOUS manifestation of quantum effects at the MACROSCOPIC scale. That is what Carver Mead was trying to emphasize! There are no classical analogue to even come close to describing such a phenomena.

Period!

Zz.

 

[ZapperZ]

Yes it seems very likely to me that CM will be able account for Superconductivity. BUT only IF, When & after completely accounting for one or two paradoxes currently only resolved by superposition! Not just coming close but actually completely explain it.
Just because there are some “attempts” by CM that kind of come close is no reason to demand that QM must do the same for superconductivity, that’s just silly.

Whoa! Really?!

I would LOVE to see this "CM will be able to account for Superconductivity". Till I see this, I'm sure you'll understand that I will that you are making a guess, or speculating at best. Come up with the order parameter that we observe in high-Tc superconductor, please. That will be a good start.

Zz.

 

[RandallB]

Whoa! Really?!
I would LOVE to see this "CM will be able to account for Superconductivity". Till I see this, I'm sure you'll understand that I will that you are making a guess, or speculating at best. Come up with the order parameter that we observe in high-Tc superconductor, please. That will be a good start.
Zz.

now really
Did you even read past the first sentence??
I’m not interested in your Classical Analogs
I expect classical solutions – and IF that is to start there is no reason for it to start with superconductivity.

Period!

 

[ZapperZ]

now really
Did you even read past the first sentence??
I’m not interested in your Classical Analogs
I expect classical solutions – and IF that is to start there is no reason for it to start with superconductivity.
Period!

Yes I did, because what I quoted was NOT the first sentence.

And I don't care where it starts and with what. If it cannot account for superconductivity, it doesn't come close to be considered on par with QM. What's wrong with that?

Zz.

 

[DrChinese]

As Vanesch pointed out early on the key difference between QM & CM is superposition. If CM can show that that is wrong, then QM is done for.

RandallB,

This is a mischaracterization of the differences between the classical world and the quantum world. There are a lot of differences, and superposition is just one. And that is ZapperZ's point. Some folks like to pick out one thing as the "main" difference: I think it was Feynman who said that the Double Slit was the biggest thing. (This can be explained with the Heisenberg Uncertainty Principle.) But such statements are not intended to be taken literally.

What should be taken literally is this: a theory which wants to compete with QM must be at least as good as QM. Before QM, physics was disconnected in a lot of areas; QM unified a lot of seemingly independent phenomena under one umbrella. And that's a good thing!

QM will never be done for. It makes no sense to talk in such terms. Even if a superior theory is adopted, its ideas will live on. We still use plenty of classical formulas because they have plenty of good applications. QM is the master of new applications because it is such a useful theory.

CM can never show superposition to be wrong. QM already showed us that superposition is right because there has been plenty of experimental support! Otherwise, it would have been rejected a long time ago - actually would never have been considered in the first place.

If someone wants to turn back the clock to classical times, the burden is on them to come up with a compelling benefit - and a theory that delivers. A "classical" theory that matches QM neither makes sense (because it offers no benefits), nor is possible (which anyone who accepts Bell's Theorem already knows).

 

[QMrocks]

No interception at all, your in play here as well. That’s correct, not in a way that would explain it for an individual particle- an expanding wave packet would be superposition.Your right that's the way he said it. The point is so what if “there's still no CM explanation of superconductivity” unless he is satisfied with the arguments already given by CM on the others what difference could it make.
Yes it seems very likely to me that CM will be able account for Superconductivity. BUT only IF, When & after completely accounting for one or two paradoxes currently only resolved by superposition! Not just coming close but actually completely explain it.
Just because there are some “attempts” by CM that kind of come close is no reason to demand that QM must do the same for superconductivity, that’s just silly.

So are you saying that EM theory is not part of CM? And SED has an alternative version of EM theory that does not invoke the idea of superposition?

 

[vanesch]

As Vanesch pointed out early on the key difference between QM & CM is superposition. If CM can show that that is wrong, then QM is done for.
So if CM is to assume superposition is invalid, that leaves several paradoxes unresolved. CM must prove it has not just a “better” solution, but a complete and real solution to at least one of the basics (entanglement, double slit, electron not crashing into protons, etc.)
The point of this thread as Vanesch kicked it off is where CM is now and what it needs to do. (Not who as an idea that should crush any CMer from even trying) Other than producing a solution a start could also be made on refuting the negative prove against CM where Bell says CM cannot work. I really don’t see how any “complete proof” can be considered complete if it doesn’t lead to that any way. Certainly for CM that should be more important than superconductivity, even if it can be developed into another form of a negative proof against CM.
As to who will win this “race” how can we tell till we know, till then I’ve never been much for giving odds, so I’ll take the odds and bet on CM.
RB

I don't think theory A can prove theory B wrong or vice versa. You can only find out 2 possibilities:
- it can be shown that theory A and theory B will make the same predictions for experiment
- theory A and theory B make, in some cases, different predictions for experiment.
If you are in the first case, it is a matter of taste and you can argue until you grow a long beard over it. The interesting case is when you're in the second case. It is then sufficient to do one of those experiments where the predictions are different and you know that at least ONE theory will be falsified.
Ok, that sounded simple. But the situation QM - CM is not that easy.
Here we have: theory A versus an entire set of not yet clearly defined theories B, call it Bag C. Clearly, Bag C does not have many predictions for many things, because they are many of them and not even written down.
What Bell did, was: well, if I can make these basic assumptions about ALL theories of Bag C, then I can show that theory A will make, in certain cases, different predictions than all the theories of Bag C.
So we know that no theory of Bag C will ever be a theory that will bring us in the first case.
The problem is that the experiments suggested are difficult to put in place, and we can not do them, exactly in that way. We can do experiments that come close and use the elements of theory A exactly where they would make different predictions, but we need experimental corrections, also suggested by theory A, which make that some theories in Bag C can do the same. This is strongly suggestive that theory A is not wrong, but it is not excluded.
And of course the main problem is that we still have a whole bag of undefined theories Bag C, so for MOST phenomena which are handled well by theory A, nothing is said by the theories of Bag C. This was ZapperZ point: telling about how it is not impossible that some theory in Bag C can do all the same is nothing else but day dreaming.
It is correct that the scientific method only discriminates between two existing theories, not between an existing theory and a set of as yet undefined theories which could potentially maybe make the same predictions.
Now, imagine that CM proponents do a lot of work and finally come up with a classical theory that matches all of QM's predictions in those areas where it has been tested. Did CM now prove QM wrong ? No, of course not: QM ALSO made all these predictions. You can now maybe have an interpretational preference for CM, but if I wanted to, I could stick to QM, and CM DID NOT PROVE QM WRONG. Are we now in case 1, where it is simply a matter of taste to prefer one theory over another ? No, because of Bell's theorem: it means that SOME predictions of the CM theory to be develloped ALWAYS will be different from the QM predictions. So we only have to do those experiments, right ? Only this time it will be clear: there will not be loopholes because the CM theory will ALSO make precise numerical predictions of the outcomes (and not just an inequality).
One of both will win (or both will loose).
Imagine that the experiment proves QM wrong: it wasn't CM who falsified QM in that case: it was experiment. So we didn't really need the CM theory to falsify QM.
Imagine that the experiment proves QM right: all the work in CM for nothing.
So the situation is this:
- for the moment we have no CM theory that makes identical predictions as QM in ALL the areas where QM was successfully tested. It is only some HOPE by some that such a theory exists and can be worked out.
- If ever their hope is satisfied and they finally DO find such a theory that can make same predictions as QM in areas such as superconductivity, atomic and molecular spectra etc... then QM and CM are at that moment on an equal footing.
- finally experiment alone will decide between them, and QM will only be proved wrong when experiment falsifies it. Also, CM could be proven wrong.

That's why I honestly don't see the point in working on a CM until QM is falsified experimentally. The reason is that you have to work a lot and hope 2 times: first to FIND the CM theory that fits current QM (I'm far from convinced that that is a reasonable thing to look for), and second that the EXPERIMENT will falsify QM, something it hasn't done since about a century. That's taking a big bet.

I think it is much more "bet efficient" to just do experiments to test QM in all possible ways. As long as QM is not falsified, I don't see the point in looking for something else. And IF QM is falsified, we'll have a clear indication into what direction to look for. The thing that CAN be interesting in looking for CM's are suggestions for experiments.

 

[RandallB]

At least you know how to stay on topic your own thread (as revised in post #3). I still feel superposition is the best single issue to set as a demarcation between CM & QM. After all HUP doesn’t explain the double slit as DrC would suggest, it only statistically measures it. It’s when you us HUP to build superposition that you can use that to build an explanation or understanding of the double slit that remains consistent within the boundaries of QM Theory. I’m not aware of any issue solved by QM that cannot at least use superposition of an individual or of multiple particles together as a QM description of the event even if there are others.

I don't think theory A can prove theory B wrong or vice versa.

And this is where your thread seems like it is being hijacked. Theory A can do well on an experiment that B has no answer to and thus IMPLY that B can never do so. And therefore ignore theory B until that experiment is addressed by B.
Proving activity in CM is pointless is zz's real point and there is nothing wrong with that – it just doesn’t belong in your thread here.
Here your looking for where CM is and what it needs to do, not for reasons to ignore or stop the effort.

Now, imagine that CM proponents do a lot of work and finally come up with a classical theory that matches all of QM's predictions in those areas where it has been tested.

Here’s where you and I disagree within the real topic. The biggest mistake CM proponents make is exactly this – just trying to match what QM has already done – that will not show anything. They must build there own experiment that that they can solve that explains more than QM can. Because if it can explain more than QM can, that experiment will be unexplainable by QM. Then is when CM will have something to really talk about.

I think it is much more "bet efficient" to just do experiments to test QM in all possible ways. As long as QM is not falsified, I don't see the point in looking for something else. ….
The thing that CAN be interesting in looking for CM's are suggestions for experiments.

But you’ll never find an experiment that can falsify QM if you’re only looking at matching what QM is already doing. If a current experiment were to find something significant and unexplainable my guess is it would be set aside as just another “wonderful weirdness of QM and/or GR” and not investigated in detail and worst of all not shared for other to consider. New ideas come from generally one of two places, 1) A new unexpected experiment or observation that demands/leads to a new idea, or 2) An original thought to explain things by; that leads to creating a new experiments or observation to confirm the idea.

I believe a CM solution must come from a new idea. CM proponents need to stop reacting with ideas just to match QM results. It will require proactive thinking to directly explain reality with CM, which means to really THINK to reach something new.
So in the context of this thread what does CM need to do – stop fretting about matching QM and set about coming up with real answers till you find one that rationally works.

“But GEE what should we think about, ….what should we solve?”
My suggestion assume superposition is wrong and has no place in a CM world.
This means several “resolved paradoxes” are no longer resolved – so solve them! Including that the Bell Theorem is somehow miss-understood or wrong (And yes I am convinced of that) and solve it correctly. No matter which one you start with. Quite whining and start thinking, you don’t get to ask giants to resolve it for you, you need to stand on their shoulders, see further, and find another path on your own.

By no means a popular thing to even try from within the scientific community. Very few like L. de Broglie and J. S. Bell spoke much about their preference for the classical as they worked from within QM. Popular or not if there is a solution in your bag C it will never be found without someone looking for it.

SO, the idea that the looking should not even be attempted; Sorry I’ve not seen anything that proves that attitude justified. In "bet efficient" terms you don’t see QM with the confidence of ‘giving odds’ that CM cannot work, because even the top QM guys admit that in their gut they don’t really understand QM. That’s why there are so many variations (String, MWI, etc) looking for a way to somehow complete QM and resolve their doubts.

 

[reilly]

It is wise, I think, to remember that QM is all about weird phenomena -- discrete atomic spectra, black body radiation, electron diffraction, photoelectric effect, atomic and molecular structure and stability, Stern-Gehrlach, the supers -- conductivity, fluidity,conductors, ... . QM is so far ahead of any other theory in describing and explaining Nature, that it is hard indeed to see how CM could be turned inside out and upside down to make nice with all, repeat, all of QM phenomena.

Note -- folks have been trying to redo CM to fit quantum phenomena for most of the last 100 years or so. While during this time the QM community has gone from Planck to strings and branes, the classical wannabes have made precious little progress, and seem to be hung-up on a very few experiments, and have contributed no new physics. (Even the Chicago Cubs have come closer to their goal than the CM => QM folks.) But, then, every once in a while, a windmill tilts and falls.

Regards,
Reilly Atkinson

 

[Careful]

I largely disagree with one statement which repeatedly is made by QM proponents. IF one would come up with a consistent CM scheme which explains all experimental outcome which is also fitted by QM, THEN the CM theory is BY FAR preferred from the ontological point of view. We would dispose at that moment of a single unifying ontology, it is shocking to see how few of you are not aware of/``in for´´ this argument.

 

[ZapperZ]

I largely disagree with one statement which repeatedly is made by QM proponents. IF one would come up with a consistent CM scheme which explains all experimental outcome which is also fitted by QM, THEN the CM theory is BY FAR preferred from the ontological point of view. We would dispose at that moment of a single unifying ontology, it is shocking to see how few of you are not aware of/``in for´´ this argument.

Why stop there? Why not just say "IF I can come up with the Granddaddy theory of everything describing the universe..."? You made a huge assumption... no, not even an assumption, a speculation, that IF so-and-so happen. But it doesn't, and there's nothing to even indicate that such a progress has been made. It has been close to 100 years since superconductivity was discovered, and classical mechanics is nowhere closer to forming an accurate description of this phenomenon than it was back then. And I haven't even started with the newer, more exotic phenomena such as the Fractional Quantum Hall effect, fractional charges, Luttinger Liquid, etc.. etc.

No, what is shocking to see is that CM proponents CONTINUE to ignore the 90000 lbs gorrila staring right in their faces. Until I brought it up, NO ONE was even considering phenomena such as superconducitvity, superfluidity, etc. as being the single most clearest manifestation of quantum phenomena. When a phenomenon has been that obvious for THAT long, it still cannot even come close to describing it accurately, doesn't this a serious shortcomming in that point of view? I am not surprised then that superconductivity is put under wraps and being swept under the carpet whenever people claim that CM can do so-and-so.

If we're playing random speculation, then I could also make the speculation that classical mechanics can never describe these phenomena, and I have more observational evidence to go by based on all the things it can't do.

Zz.

 

[Careful]

Why stop there? Why not just say "IF I can come up with the Granddaddy theory of everything describing the universe..."? You made a huge assumption... no, not even an assumption, a speculation, that IF so-and-so happen. But it doesn't, and there's nothing to even indicate that such a progress has been made. It has been close to 100 years since superconductivity was discovered, and classical mechanics is nowhere closer to forming an accurate description of this phenomenon than it was back then. And I haven't even started with the newer, more exotic phenomena such as the Fractional Quantum Hall effect, fractional charges, Luttinger Liquid, etc.. etc.
QUOTE]
I just told a few posts ago that the Fractional quantum hall effect has a (at least a partial) classical explanation in terms of fractional charges. I will ask you a silly question : do you know of any derivation of superconductivity which originates from first principles ?? BCS theory rests upon some certain (almost classical) assumptions, why would a classical theory exclude the formation of Cooper pairs ?

 

[ZapperZ]

I just told a few posts ago that the Fractional quantum hall effect has a (at least a partial) classical explanation in terms of fractional charges. I will ask you a silly question : do you know of any derivation of superconductivity which originates from first principles ?? BCS theory rests upon some certain (almost classical) assumptions, why would a classical theory exclude the formation of Cooper pairs ?

Are you on a fishing expedition? Please show exactly where "BCS theory rests upon some certain (almost classical) assumptions". And in case you missed it, take note that the BCS theory DOES start from First Principles, AND that it can be derived either via Variational method and Field Theoretic method, per what is described in Tinkham's text.

And if you have a "partial" classical formulation of fractional quantum hall effect, I would appreciate it if you could submit it to PRL to challenge Laughlin's formulation of his quasiparticles.

Zz.

 

[vanesch]

SO, the idea that the looking should not even be attempted; Sorry I’ve not seen anything that proves that attitude justified. In "bet efficient" terms you don’t see QM with the confidence of ‘giving odds’ that CM cannot work, because even the top QM guys admit that in their gut they don’t really understand QM. That’s why there are so many variations (String, MWI, etc) looking for a way to somehow complete QM and resolve their doubts.

QM is strange indeed, but it is my impression that the strangeness is not an impossible difficulty ; at least it works!
I agree with you that people who are interested, can always continue to look for that holy grail in Bag C. Only, as long as they haven't found anything, it's maybe not very useful to have a lot of wishful thinking about how it will be nice once they've found it. IT MIGHT NOT BE THERE.
I could also call for more investigation into the hidden treasure of the Templars, and then talk about all the things I'm going to do with the money, and how other people working for their meager salary are profoundly misguided. The treasure might not be there. Now, for people who have a personal conviction that they will find it, please go ahead ! I've wondered how it cannot occur to certain CM proponents that their theory might simply not exist. Nevertheless, if they are motivated to look for it, why not let them, this can always give rise to interesting discussions. But UNTIL they've found it, I don't think it makes a lot of sense to talk about it as if such a theory exists. And finding it means: reproducing about all the successes of QM until now. Not: hoping that it will, but doing so.

 

[Careful]

Are you on a fishing expedition? Please show exactly where "BCS theory rests upon some certain (almost classical) assumptions". And in case you missed it, take note that the BCS theory DOES start from First Principles, AND that it can be derived either via Variational method and Field Theoretic method, per what is described in Tinkham's text.
And if you have a "partial" classical formulation of fractional quantum hall effect, I would appreciate it if you could submit it to PRL to challenge Laughlin's formulation of his quasiparticles.
Zz.

Ah, it always useful to fish, that is the only way to learn ! But it is exactly Laughlin who provided at the same time this classical picture ! I assume that what you mean by first principles is that Tinkham describes an *effective* field theory based upon symmetry principles and some other simplifying assumptions ? It is long ago that I did solid state physics : so you might wish to explain us what is *essentially* quantum in the effect of superconductivity. To start with, what quantum ingredients are used??

 

[ZapperZ]

Ah, it always useful to fish, that is the only way to learn ! But it is exactly Laughlin who provided at the same time this classical picture ! I assume that what you mean by first principles is that Tinkham describes an *effective* field theory based upon symmetry principles and some other simplifying assumptions ? It is long ago that I did solid state physics : so you might wish to explain us what is *essentially* quantum in the effect of superconductivity. To start with, what quantum ingredients are used??

Sorry, no go. One only needs to look at the starting point of the BCS theory, and they're everywhere. You were the one who claimed there are "classical" ingredients to this. Yet, you CLEARLY are refusing to provide evidence to back it up. Please show me exactly where in the BCS theory is the "classical assumption" made.

And while you're at it, please show where in Laughlin's PRL paper on FQH did he "provide" the classical picture.

Zz.

 

[Careful]

Sorry, no go. One only needs to look at the starting point of the BCS theory, and they're everywhere. You were the one who claimed there are "classical" ingredients to this. Yet, you CLEARLY are refusing to provide evidence to back it up. Please show me exactly where in the BCS theory is the "classical assumption" made.
And while you're at it, please show where in Laughlin's PRL paper on FQH did he "provide" the classical picture.
Zz.

Really, could you enlighten then this poor mind which does not see ?? This is just a friendly question ; until now in our conversations you have only said no no and I have often backed my claims up with concrete references and reasons saying yes yes - this has happened many times also with other PF mentors. Now, this is clearly your field of expertise (I am just a poor GR kid) so you should radiate on the classical GR world here, I am all ears. All I said moreover is that I do not see anything exclusively quantum in the possibility of Cooper pairs; so I would really welcome your insight in WHY it is so, perhaps you could erase my blindness ? I will cite you from the laughlin reference:

**Laughlin discovered a useful and beautiful analogy between the interacting electrons of the fractional quantum Hall effect and a one component classical plasma of particles interacting with a logartihmic potential ... ** I said there was a analogy known up to a certain level; I did not claim more.

So, I think this should be a definite ``yes go´´. It is easy to have criticisms on every attempt when you rocksolidly stick to what you know best. It would be much easier for me not to look for anything else ! So perhaps we can turn this into a constructive discussion.

 

[ZapperZ]

Really, could you enlighten then this poor mind which does not see ?? This is just a friendly question ; until now in our conversations you have only said no no and I have often backed my claims up with concrete references and reasons saying yes yes - this has happened many times also with other PF mentors. Now, this is clearly your field of expertise (I am just a poor GR kid) so you should radiate on the classical GR world here, I am all ears. All I said moreover is that I do not see anything exclusively quantum in the possibility of Cooper pairs; so I would really welcome your insight in WHY it is so, perhaps you could erase my blindness ? I will cite you from the laughlin reference:
**Laughlin discovered a useful and beautiful analogy between the interacting electrons of the fractional quantum Hall effect and a one component classical plasma of particles interacting with a logartihmic potential ... ** I said there was a analogy known up to a certain level; I did not claim more.
So, I think this should be a definite ``yes go´´. It is easy to have criticisms on every attempt when you rocksolidly stick to what you know best. It would be much easier for me not to look for anything else ! So perhaps we can turn this into a constructive discussion.

Sorry, but you call this a "constructive discussion"?

You made an off-the-cuff remark that BCS theory had a classical component. When I question you to show specifically where this is, you cite poor memory. I find it incredulous that you would use that as an excuse, yet you make no qualms in making a statement about BCS theory. So where is your "concrete references" now?

I have no desire to tell you about BCS theory when this is one of the, if not the, most well-publicized theory of all time. The BCS Hamiltonian is known to everyone who would even look at a Superconductivity text. This thing is well established. What is NOT well-established is what you claim. When someone is making non-standard claim about an established principle, shouldn't the responsibility falls on that someone who produce the evidence and NOT the other way around?

And since WHEN do we do physics simply by citing quotes. I cited Carver Mead not just for his quotes, but because I understand intimately the subject matter he was discussing and not just superfically the statements he made. I asked you to look at the Laughlin's PRL paper and show me where he actually did anything "semi classical" to derive his wavefunction for FQHE. Again, you could not produce such a thing.

And you wanted a constructive discussion? Oy vey!

Zz.

 

[Careful]

There are pleanty of people around here asking about well established physics and they get a perfectly good aswer. So, why should I be treated differently ??


** You made an off-the-cuff remark that BCS theory had a classical component. When I question you to show specifically where this is, you cite poor memory. **

I did not make such claim, I said I saw no reason why Cooper pairs could not be formed by a classical principle. I am asking you here for your insights why this should not be so and also for your expertise what is so quantum about superconductivity.

Can you provide me with an internet reference where I can find a DERIVATION of BCS Hamiltonian from the physical lattice structure and the detailed interactions ?? Looking at the Hamiltonian only tells me that Cooperpairs are put in by hand. I am just interested in this, that's all.


**
And since WHEN do we do physics simply by citing quotes. **

So what is wrong with this quote which you can find in the nobel lecture. If I misunderstood what is meant, I am sure you can clarify it. Moreover, it is your responsability to explain to what degree this well established theory is derived from first principles and giving the effective Hamiltonian does not explain anything unless you provide a reference which shows this Hamiltonian is reasonable.

 

[member 11137]

Can you provide me with an internet reference where I can find a DERIVATION of BCS Hamiltonian from the physical lattice structure and the detailed interactions ?? Looking at the Hamiltonian only tells me that Cooperpairs are put in by hand. I am just interested in this, that's all.
**
And since WHEN do we do physics simply by citing quotes. **
So what is wrong with this quote which you can find in the nobel lecture. If I misunderstood what is meant, I am sure you can clarify it. Moreover, it is your responsability to explain to what degree this well established theory is derived from first principles and giving the effective Hamiltonian does not explain anything unless you provide a reference which shows this Hamiltonian is reasonable.

Hey people: not enougth war on the Earth ? Carefull, I am not a specialist and not a mentor of this website. I also don't know your level and if it can help you, but did you try at the following adress ?
http://ocw.mit.edu/index.html
I have found an interesting lecture on the BCS (perhaps only a special case and to easy for you; I don't know; sorry)

 

[Careful]

Hey people: not enougth war on the Earth ? Carefull, I am not a specialist and not a mentor of this website. I also don't know your level and if it can help you, but did you try at the following adress ?
http://ocw.mit.edu/index.html
I have found an interesting lecture on the BCS (perhaps only a special case and to easy for you; I don't know; sorry)

Hi, thanks, will take a look later on. What I am interested in is a derivation of an effective field theory of Cooper pairs from an exact lattice field theory (starting from known interactions). Screening on the web, I bumped upon the following reference:
cond-mat/0006097 where the authors claim to have done this in a perturbative approach for the TWO dimensional, Euclidean, two component Ginzburg-Landau model. I am not a condense matter physicist, so I wonder wether ZapperZ knows if more progress is made in this direction (in 3+1 dimensions for example). The point I was trying to make here, is that you still have to DERIVE the Cooper pair mechanism from first principles before you can claim that QM *predicts* superconductivity *from first principles*. I do not dispute that the idea of Cooper pairs and the associated BCS Hamiltonian do a good job, but that is not sufficient. But I can be wrong here, and just be ignorant of more significant progress. That is why I ask an expert like ZapperZ.

Cheers,

Dr. Careful

 

[reilly]

I largely disagree with one statement which repeatedly is made by QM proponents. IF one would come up with a consistent CM scheme which explains all experimental outcome which is also fitted by QM, THEN the CM theory is BY FAR preferred from the ontological point of view. We would dispose at that moment of a single unifying ontology, it is shocking to see how few of you are not aware of/``in for´´ this argument.

Well, Careful, when that great CM theory arrives, then we'll worry about ontological nicieties. To me it's shocking that anyone would would be shocked about hypotheticals, even within the arcanities of QM. How in the world, do you do all of chemistry and atomic physics, including emission and absorbtion spectra, and QED to some 13 decimal places, without QM? Curious minds want details, physics, not speculative philosophy. How do you go about producing this theory of the future?

Regards,
Reilly Atkinson

 

[Sherlock]

It seems to me that the main problem for a CM description of quantum phenomena is that we can't see the media in which quantum disturbances are occurring in nature. In order to say anything at all about quantum phenomena, they have to be amplified (sometimes through several, ingeniously designed, steps) to scales which are amenable to our sensory perception. This doesn't mean from spatially small to large necessarily. It means from disturbances in an undetectable medium (or media) to disturbances in detectable media. So, I'm thinking of the necessary transformations to observable phenomena as going through energy scales. Is this an ok way of looking at it? Is there a better way?

In this way of looking at the problem, there doesn't seem to be a theoretical solution to the problem of rendering the nature of quantum phenomena more amenable to a description in terms of analogs from our sensory experience of nature than it already is. Given more sensitive instruments and even more ingenious detection schemes, it seems that as (rather, if) quantum phenomena become more amenable to CM descriptions, then those descriptions will be adopted. But, for now, they are rendered as classically as is possible it seems.

 

[Careful]

Well, Careful, when that great CM theory arrives, then we'll worry about ontological nicieties. To me it's shocking that anyone would would be shocked about hypotheticals, even within the arcanities of QM. How in the world, do you do all of chemistry and atomic physics, including emission and absorbtion spectra, and QED to some 13 decimal places, without QM? Curious minds want details, physics, not speculative philosophy. How do you go about producing this theory of the future?
Regards,
Reilly Atkinson

You seem to have missed that my statement was a reaction on the assertion that a CM theory of microphenomena is only worthwhile when (a) a future experiment falsifies QM (b) when it gives easily rise to new predictions. Oh for sure I want details, and SED and the self field approach are far from speculations; they are useful first rigorous steps in my opinion. I seems to me that when the scientific community wants to invest millions of dollars into ``constructs´´ such as string theory, supersymmetry, LQG and so on, which do not have even produced a single experimental prediction in 30 years (supersymmetry is still waiting for falsification and LQG is still digesting the Hamiltonian constraint); then for sure one might give CM a good try. Since you are such a curious mind, why don't you tell me where QFT derives an effective theory of cooperpairs from first principles ??

 

[DrChinese]

I seems to me that when the scientific community wants to invest millions of dollars into ``constructs´´ such as string theory, supersymmetry, LQG and so on, which do not have even produced a single experimental prediction in 30 years (supersymmetry is still waiting for falsification and LQG is still digesting the Hamiltonian constraint);

There is a difference, as you should know. Supersymmetry promises a unified theory, which is a specific benefit. CM promises absolutely nothing, and I do mean nothing as in nada and zilch; and it is completely ridiculous to claim otherwise. Why should anyone invest a penny in it? There is only one reason, and that is BLIND FAITH.

Of course, the search for a TOE may not lead to anything anyway, as perhaps there is no unification of GR and QFT.