The Rovelli Point of Wrong Turn

[Gebar]

The "Rovelli Point of Wrong Turn"

In 2003 Carlo Rovelli wrote a paper entitled "A dialog on quantum gravity" (Int.J.Mod.Phys. D12 (2003) 1509-1528, http://www.arxiv.org/abs/hep-th/0310077" ). There, in the form of a dialog between professor Simp, a high energy physicist, and Sal, a graduate student who has decided to study loop gravity, Rovelli gives a "State of the Union" (read Unification) account of theoretical physics.

The paper gives a picture of the theory as well as a comment on the sociological effects of the String Wars, but it also makes a point that I think is very important and may lead to a very useful question. It concerns the historical course of theoretical physics through the maze of possible theoretical formulations in its effort to arrive at the one that will describe satisfactorily physical reality.

And I quote:

...
Simp – It is not the fault of the theoretical physicist if the path of the natural evolution of the research has lead to a theory which is very complicated.

Sal – And if it was the fault of the theoretical physicist? I suppose when you say “the path of the natural evolution of the research” you mean the line that goes along Fermi theory, QED, SU(2)×U(1), QCD, the standard model, and then grand unified theories, the revival of Kaluza-Klein, supersymmetry, supergravity, . . . strings. . .

Simp – Yes.

Sal – But what if this “path of natural evolution” has taken a wrong turn at some point. Seems to me there is precise break along this path.

Simp – What do you mean?

Sal – Dirac predicted the positron, and it was found. Feynman and friends developed a calculation method for photon-electron interactions, and it works to devastating precision. Weinberg Glashow and Salam predicted the neutral currents and they were found, and the W and Z particles and Carlo Rubbia found them, precisely where predicted, just to name some . . .

Simp – So?

Sal – And then?

Simp – Then what?

Sal – Then the Veneziano formula predicted a very soft high energy behavior of the amplitudes, and nature was not like that. The grand unified theories predicted proton decay at some precise scale, and proton decay was not found where expected. Kaluza-Klein theory, revived, predicted the existence of a scalar field that was searched by Dicke, and not found. Supersymmetry predicted the supersymmetric particles and these were not found where repeatedly annunciated. Extra dimensions did not show up where recently suggested by string theory. . .

Simp – But the proton may take a bit longer to decay, the masses of the supersymmetric partners may be higher . . .

Sal – Of course, they “might”. Everything is possible. But the cut between the previous fantastic sequence of successful predictions right on the mark, and, on the other hand, the later series of unsuccesses is striking. Before, experimental particle physicists were always smiling and walking like heroes: looked like God was reading Phys Rev D and implementing all suggestions of the theorists. Nowadays, thanks god they are still busy figuring out aspects of the standard model, because all the new physics that theoreticians have suggested wasn’t there . . .

Simp – Theory has always made wrong predictions.

Sal – Yes, but also right predictions, and those are missing, after the standard model.

Simp – It is because energies of new predicted physics are too high.

Sal – Not at all. There have been plenty of predictions that were well within reach. They just were wrong.

Simp – So, what do you make of this?

Sal – That perhaps Nature is telling us that our path of theoretical research has taken a wrong turn, at some point . . .

Simp – This is not a proof.

Sal – Of course. The fact is that we do not know. ...
...​

(Boy, that bit about God and Phys Rev D was too much.) :rofl:

And so, I would like to pose exactly this question here. Where do you think this wrong turn was made? At which point after (or within) the Standard Model?

Or, you may think there is no wrong turn anywhere; that the historical course of theoretical physics is the best possible. (This should probably include an explanation of the cause of the "precise break along the path" that will not involve energy levels.)

Or, finally, you may take the completely heretical view that the wrong turn was made even before the Standard Model. This seems like crackpot country, but you never know.

So, place your bets, ladies and gentlemen! (This may seem inappropriate, but at the current state of affairs what one believes on this point does seem like a gamble.)

 

[selfAdjoint]

I wou;d say it was when Fadeev and Popov quantized nonabelian gauge therory and found their ghosts (foreseen by Feynmann) as necessary to preserve unitarity within gauge freedom. Once physicsts had gulped and swallowed that, they would gulp and swallow anything.

 

[Careful]

**
Or, finally, you may take the completely heretical view that the wrong turn was made even before the Standard Model. This seems like crackpot country, but you never know.

So, place your bets, ladies and gentlemen! (This may seem inappropriate, but at the current state of affairs what one believes on this point does seem like a gamble.) **

I think your way of presenting it is far too simplistic as is usually the case for people making polls. Clearly, the standard model, QM and all this are good approximations to nature; the far more difficult question being on what scales one has to take these theories seriously. For example, no serious local realist (which you probably would consider a heretic) would doubt the accuracy of the standard model in high energy experiments, however he/she could say that the one particle interpretation of QM is incorrect (which is actually consistent with the statistical interpretation of QM). Strictly speaking, it is rather easy to construct local hidden variable models which reproduce the QFT correlation functions. Given the fact that in QFT only correlation functions are computed, there is even no contradiction at this level ! So, the game is much more subtle and the possibilities you offer are irrelevant; local realism was disposed of ``socially'' prior to the birth of the standard model, but nothing really went wrong in the standard model provided you interpret it correctly.

What could very well have gone wrong, is the possibility that the question of quantum gravity is meaningless or posed way too early to say the least.

Careful

 

[Gebar]

Careful:

The question was very specific (if you care to address it, of course; I can perfectly well accept your answer as it is): how do you explain this "precise break along the path" of theory development in terms of the successful predictions made up to a point and the unsuccessful ones made from that point onwards.

 

[Careful]

Careful:

The question was very specific (if you care to address it, of course; I can perfectly well accept your answer as it is): how do you explain this "precise break along the path" of theory development in terms of the successful predictions made up to a point and the unsuccessful ones made from that point onwards.

You misread me: the question is fine, the *options* you offer in your poll are not (that is what I said literally) - they do not reflect the subtlety in foundational issues we are confronted with today. I mean for all practical purposes, we have incompatible theories which give very accurate predictions in different domains of length (energy) scales - so there is no lack of prediction, there is only lack of a unified concept. In this matter, I fear that some frameworks were pulled out of context, and extrapolated to domains where they don't belong. More on that later.

Careful

 

[arivero]

Of course there is a wrong turn very early: to assume that the angular momentum can happen [and, particularly, that it can change,] in quantities as small as one wants. But it happenned too many time ago. Two close friends of the author of this assumption convinced him to retain publication until the argument were closely examined, and this delay went into a priority dispute. It is the only "before standard model" thing I can imagine.

 

[marcus]

Of course there is a wrong turn very early: to assume that the angular momentum can happen [and, particularly, that it can change,] in quantities as small as one wants. But it happenned too many time ago. Two close friends of the author of this assumption convinced him to retain publication until the argument were closely examined, and this delay went into a priority dispute. It is the only "before standard model" thing I can imagine.

this whets my curiosity. would you please give a little more detail?

 

[arivero]

this whets my curiosity. would you please give a little more detail?

a old history. The first excuse of Newton in the Dispute was that two very close friends of him have suggested him to do not publish because of some doubts they raised. He does not tell us which the doubts were, but historians have read and reread the notebooks and early manuscripts of the Principia and it seems that the heaviest edited "proposition" is the one of the angular momentum under central forces. I have been a bit sloopy in the previous remark, because it not exactly the variation of angular momentum which is at stake (after all, it does not change), but the need of taking smooth paths during the process of proof, and the adequate conditions for convergency. In fact the drawing of the proof of this theorem closely remembers Feynman's path.

This wrong turn was, in principle, corrected by Nature, when She told us that the angular momentum in 3D was to be token always as integer multiple of a quantity, and then She hinted Pauli that this was to be interpreted as discrete derivatives. Pauli gave the hint to Heisenberg, and Heisenberg to Born and Jordan.

But Meanwhile, the XIXth century saw the development of Lagrangian Mechanics, Hamilton Mechanics, and Classical Field Theory. The history of the second half of the XXth century is to try to correct the misunderstanding also in these newer mechanics.

 

[Careful]

***
This wrong turn was, in principle, corrected by Nature, when She told us that the angular momentum in 3D was to be token always as integer multiple of a quantity, and then She hinted Pauli that this was to be interpreted as discrete derivatives. Pauli gave the hint to Heisenberg, and Heisenberg to Born and Jordan.

But Meanwhile, the XIXth century saw the development of Lagrangian Mechanics, Hamilton Mechanics, and Classical Field Theory. The history of the second half of the XXth century is to try to correct the misunderstanding also in these newer mechanics.**

Euh, correlation functions and operators in quantum mechanics and QFT are usually smoother (often analytic) than the classical paths in Lagrangian and Hamiltonian mechanics are (and the number of smoothness/continuity notions in QM are at least four times more numerous than in ordinary CM). You refer to the fact that the non-smooth paths dominate the path integral sum of the free particle kernel, so what, that does not mean anything. You can figure out similar models for classical field theory : cfr. cellular automaton models for the Maxwell field. Moreover, nature did not tell us at all that angular momentum *is* quantized ; a continuum theory can cover very well for the appearant discreteness in the measurement outcome.

Careful

 

[arivero]

***
But Meanwhile, the XIXth century saw the development of Lagrangian Mechanics, Hamilton Mechanics, and Classical Field Theory. The history of the second half of the XXth century is to try to correct the misunderstanding also in these newer mechanics.**

Euh, correlation functions and operators in quantum mechanics and QFT are usually smoother

Indeed I am telling that quantum mechanics is a better tool than classical mechanics.

My last parragraph aimed to state that while the 1st third of the XXth century was about quantisation of classical almost Newtonian things, the second half was after quantisation of field theories and other more dreadful beasts emanating from the XIXth century mechanics.

 

[arivero]

Now that was the "old wrong turn". To me, the modern wrong turn is the interpretation mismatch between Wilson-Kogut-Etal renormalisation group and perturbative renormalisation group. We have started to discuss about it in another thread.

 

[Careful]

**Indeed I am telling that quantum mechanics is a better tool than classical mechanics. **

Funny enough, I don't even disagree that it is a better TOOL. The founding fathers just saw something which defied what they knew about classical mechanics and developped mathematical equations designed to match the observed statistical predicition - so that is a huge shortcut in our ``understanding'' .

**
My last parragraph aimed to state that while the 1st third of the XXth century was about quantisation of classical almost Newtonian things, the second half was after quantisation of field theories and other more dreadful beasts emanating from the XIXth century mechanics. **

Euh, dreadful beasts ??! I have been repeatedly mentioning that experiment cannot even distinguish between these beautiful classical field theories and undefined quantum whatsoevers (they are not even theories yet). And I guess you are going to tell now that spin is not a continuous quantized variable ?

 

[vanesch]

My personal feeling is that the "wrong turn" was made when theorists stopped looking at experimental data, and tried to go far beyond what was experimentally hinted at.
It never happened before that theories "came out of the blue" with no experimental hints.
Newton was based upon Kepler's observations. Maxwell was based upon countless empirical laws. Special relativity was based upon a re-interpretation of the symmetry group of the Maxwell equations (the Lorentz transformations) which had already some empirical success.
The closest hit to "a theory out of the blue" was general relativity, but apart from the mathematical difficulty, there was a basic guiding principle and it was "sufficient" to work this out. And even there, there WAS some empirical suggestion (the perihelion shift of Mercury).
Quantum theory was "shoved down the throat" of theorists from spectroscopy (Balmer series and all that). QFT had a difficult emerging, and was essentially guided by some empirical data like the Lamb shift. The entire standard model was a theoretical fit on a huge amount of experimental data, where concepts were introduced in order to explain phenomenologically observed regularities.

And then, theorists left off, and went for a "beauty contest". They invented unified groups (because U(1) x SU(2) x SU(3) was "ugly"), they invented supersymmetry, they invented strings...

It is exactly at the point where theorists didn't try anymore to model experimental data, but where they entered in beauty contests independent of experiment, that wrong predictions came out as indicated here before.

 

[selfAdjoint]

"Why sometimes I've believed six impossible things before breakfast", said the White Queen in Through the Looking Glass. It's before MY breakfast this morning so let me see if I can find six impossible things that physicists still believe in.

1. The big wave function; it spreads to the end of the universe, but when somebody in Podunk does a measurement it all collapses. Pop! Goes the wave function.
2. Path Integrals. Feyman's examples in NRQM are so pretty and he is by every account a mighty genius, and all those java applets of toy situations are so impressive, but Wick rotation? Can't we admit it's an unbeautiful kludge that nobody would take seriously if it weren't essential to save us from seeing that the great man's celebrated method... doesn't work.
3. Virtual particles. You knew they would be in here but "off the mass shell?" I ask you, Energy squared less than zero, and what do we know about squares less than zero?
4. Fadeev-Popov ghosts. The ghosts are your friend! They are essential to preserving unitarity among all those gauge transformations. Fermions with boson behavior; goodbye spin-statistics. Oh wait ! They're "off the mass shell" again like virtual particles. Should count as TWO impossible things but I'll stand you a twofer.
5. Invisible extra dimensions. Curled up in weeny little balls they are; but in an earlier day any physicist whose theory told him the dimension of spacetime is 26 or 10 or whatever, would have abondoned it as a bad job.
6. And lastly and very much leastly, the landscape. I don't think there is anything I could say about this abortion that some famous physicist hasn't said already.

When was the wrong turn? When people started taking Niels Bohr seriously!

 

[Gebar]

Ah, the infamous Wrong Turn at Copenhagen! I'll buy that.

 

[marcus]

When was the wrong turn? When people started taking Niels Bohr seriously!

so it could be that Bohr did not make the wrong turn himself.

Maybe he escaped that self-delusion, and it was left to other people later to "re-ify" or "ontologize" the wavefunction framework for handling information that he offered them.
("re-ify" = thing-ify = mistakenly imagine that it is a real thing)

Ah, the infamous Wrong Turn at Copenhagen! I'll buy that.

But perhaps you cannot so easily locate the wrong turn geographically, or pin the blame on Bohr.

Personally i do not know much of the history but I think Bohr said something like QM is not about what is in nature, it is about what we can SAY about nature----that is, it is about information: what correct statements an observer can make based on what he or she has observed.

This leaves all the room in the world open for people to construct ontologies, if they want to construct them and they are not satisfied with the traditional intuitive idea of what is real.

But those who tried to promote Bohr's information theoretical QM to an idea of fundamental existence----so as to enshrine the big wave function as existing like some real object----these people may have been deluding themselves. I would like to absolve Bohr and say he did not tell them to do it

 

[selfAdjoint]

Before there was QM there was the "Old Quantum Theory". It was entirely the work of Bohr, and it was frankly magic; the electrons in their shells did not obey the known laws of physics, but no explanation or even description was given as to how that should be so. Once physicsts had got used to that (It was successful in accounting for gross features of the spectrum of Hydrogen, but failed at every other task) the Heisenberg-Schroedinger QM came as a breath of common sense!

 

[marcus]

I see what you mean. In that sense the mistake you refer to was when people started taking Niels Bohr original idea seriously. (but I think maybe you are joking )

I am hopeful about something Baez said roughly like this:
in its basic outlines QM resembles a theory of spacetime, and some things that seem counterintuitive or paradoxical about QM are very intuitive when you look at the counterpart in spacetime geometry (nCob)

so one can hope that there is something more fundamental than QM which will make better sense.

and it will be a theory of spacetime (and material as well) that will among other things explain why QM works so well as a theory of asking questions and getting answers

and since i am engaging in hopeful or wishful thinking I will go all the way and say something else:

I think that to construct an ontology on the basis of QM, and to imagine that the wavefunction is really there
(and that it has occasional fits of epilepsy and collapses foaming at the mouth when someone in Podunk does something) is simply a case of PREMATURE REIFICATION.

I liked your Podunk example.I think that people get into this "premature ontology" business when they imagine that QM must be the final theory, so, they ask, WELL if you do not make an ontology with one or more wavefunctions, then what is the matter with you? don't you have any ontology? don't you believe in ontology? what are you, some kind of solipsist?

and I say that no I am not a solipsist or anything, i believe it is possible to have a good ontology SOMEDAY, but I think it is premature to try to get it by bronzing Schroedinger's 1927 babyshoes. One should be patient and live with a traditional commonsense ontology a little more. QM is not so close to a final theory that one can make therefrom a likeness of nature.

 

[marcus]

This strikes me as a really good list, I would just like to see Bohr absolved of any wrong-doing.

"Why sometimes I've believed six impossible things before breakfast", said the White Queen in Through the Looking Glass. It's before MY breakfast this morning so let me see if I can find six impossible things that physicists still believe in.

1. The big wave function; it spreads to the end of the universe, but when somebody in Podunk does a measurement it all collapses. Pop! Goes the wave function.
2. Path Integrals. Feyman's examples in NRQM are so pretty and he is by every account a mighty genius, and all those java applets of toy situations are so impressive, but Wick rotation? Can't we admit it's an unbeautiful kludge that nobody would take seriously if it weren't essential to save us from seeing that the great man's celebrated method... doesn't work.
3. Virtual particles. You knew they would be in here but "off the mass shell?" I ask you, Energy squared less than zero, and what do we know about squares less than zero?
4. Fadeev-Popov ghosts. The ghosts are your friend! They are essential to preserving unitarity among all those gauge transformations. Fermions with boson behavior; goodbye spin-statistics. Oh wait ! They're "off the mass shell" again like virtual particles. Should count as TWO impossible things but I'll stand you a twofer.
5. Invisible extra dimensions. Curled up in weeny little balls they are; but in an earlier day any physicist whose theory told him the dimension of spacetime is 26 or 10 or whatever, would have abondoned it as a bad job.
6. And lastly and very much leastly, the landscape. I don't think there is anything I could say about this abortion that some famous physicist hasn't said already.

If I had to guess as to where a misstep occurred in the last century, it would be a sin of omission---in NOT taking Gen Rel seriously.

Probably they should have put more effort into devising a General Relativistic Quantum Physics.
(kind of thing you see Baez friends doing, linking nCob to Hilb, the former being a general relativity animal and the latter a quantum animal.)

Perhaps late 20th physicsists were seduced by GEOMETROLOGY, which is an addictive practice analogous to ASTRology and NUMERology.
As when people get hooked on inventing formulas that calculate the right numbers----because of the richness of numerical formulas it seems possible to get formulas that produce any result you want. So likewise they can get hooked the same way on differential geometry and all the beautiful machinery of manifolds. Somewhere i heard the phrase "accursed fecundity of differential geometry" applied to late 20th century theorizing.

And maybe the Geometrology hocus pocus distracted them from confronting the job of taking Einstein seriously and devising a general relativistic quantum physics.

 

[Gebar]

Well, I'll second that. GR showed that gravity's "spooky action at a distance" is curved spacetime. The next step would be to see how this could also hold true for EM forces. Kaluza did this, but he was ignored, AFAIK because nobody could see the fifth dimension. And so the compactification thing started with Klein. What I haven't understood is why we flatlanders should be able to see the fifth dimension --which could also provide perhaps non-local hidden variables. But instead people went the other way, and instead of turning EM into spacetime geometry like GR the turned GR into EM with virtual gravity particles.

 

[selfAdjoint]

I see what you mean. In that sense the mistake you refer to was when people started taking Niels Bohr original idea seriously. (but I think maybe you are joking )

Call it kidding on the square. As a charter member of the "silent" (we said "ironic") generation, I am prone to it. I do feel that over his long career of inspiring younger physicists which stamped his ideas on 20th century physics, he was overall a bad influence. I wish Pauli had played a larger prt and Bohr a smaller one in shaping the first quantum generations.

I am hopeful about something Baez said roughly like this:
in its basic outlines QM resembles a theory of spacetime, and some things that seem counterintuitive or paradoxical about QM are very intuitive when you look at the counterpart in spacetime geometry (nCob)

Baez in this is basically an algebraic quantumist; see the book he wrote with Siegel. So if he shows that the way Hilbert spaces act is closely parallel to the way cobordism acts that's to be seen in a context where quantum field theory is a net of star-algebras.

so one can hope that there is something more fundamental than QM which will make better sense.

and it will be a theory of spacetime (and material as well) that will among other things explain why QM works so well as a theory of asking questions and getting answers

and since i am engaging in hopeful or wishful thinking I will go all the way and say something else:

I think that to construct an ontology on the basis of QM, and to imagine that the wavefunction is really there
(and that it has occasional fits of epilepsy and collapses foaming at the mouth when someone in Podunk does something) is simply a case of PREMATURE REIFICATION.

I just broke down today and read something by Barut, whom careful is always recommending. And you know? He builds up from interacting an ordinary EM wave with a Dirac equation - he takes the Fourier transform and just plugs it in and breaks out the resulting nonlinear expression into terms, in which he can identify three "self interaction terms" which he shows govern the Lamb Shift and the other biggy successes of QED. And what did this say to me? Why it reminded me that Einstein's UFT does Dirac (and not just in the sense of support, but in the sense of "generate from the geometry", this is shown by Hlavaty) and the same theory with Schroedinger's mods does EM in the same sense (Shifflett) , so the materials for Barut's revolution are to hand in the old rejected UFT of the two real greats of 20th century physics. (Couldn't resist adding) And no extra dimensions about that; just use a general tensor instead of a pretty symmetric one for your fundamental starting point.

I liked your Podunk example.

I shouldn't have mocked Podunk. I have been in Peoria (as in "Will it play in...") and it's a nice town, and no more a boonie than where I'm living now. Course the way my neighbors vote, maybe that IS the boonies!

I think that people get into this "premature ontology" business when they imagine that QM must be the final theory, so, they ask, WELL if you do not make an ontology with one or more wavefunctions, then what is the matter with you? don't you have any ontology? don't you believe in ontology? what are you, some kind of solipsist?

Physicsts have ALWAYS been reifiers. It goes back to the Stoic philosophers turning Appolonius and Ptolemy's epicycles and deferents into "crystal spheres" mysteriously interpenetrating. And you recall those nineteenth century winners, Caloric (reified heat) and the luminiferous ether. And Maxwell may have been a little kidding on the square with his cogwheel model of the EM field, but his friend Tait was dead serious about his vortices.

and I say that no I am not a solipsist or anything, i believe it is possible to have a good ontology SOMEDAY, but I think it is premature to try to get it by bronzing Schroedinger's 1927 babyshoes. One should be patient and live with a traditional commonsense ontology a little more. QM is not so close to a final theory that one can make therefrom a likeness of nature.

Good attitude. I have to say that I think that word solipsist is just a bully word to make opponents quail and back down. Nuts to that!

 

[vanesch]

The big wave function; it spreads to the end of the universe, but when somebody in Podunk does a measurement it all collapses. Pop! Goes the wave function.

It might be. But the most suspicious thing is with the "pop", no ?

[*]Path Integrals. Feyman's examples in NRQM are so pretty and he is by every account a mighty genius, and all those java applets of toy situations are so impressive, but Wick rotation? Can't we admit it's an unbeautiful kludge that nobody would take seriously if it weren't essential to save us from seeing that the great man's celebrated method... doesn't work.
[*]Virtual particles. You knew they would be in here but "off the mass shell?" I ask you, Energy squared less than zero, and what do we know about squares less than zero?
[*]Fadeev-Popov ghosts. The ghosts are your friend! They are essential to preserving unitarity among all those gauge transformations. Fermions with boson behavior; goodbye spin-statistics. Oh wait ! They're "off the mass shell" again like virtual particles. Should count as TWO impossible things but I'll stand you a twofer.

Here, I don't follow you. Nobody takes these things as "real", right ? They are tools to calculate a unitary transformation (or elements of it).
Feynman path integrals are a convenient trick to calculate a matrix element, and if you prefer to do a series devellopment, certain factors in it integrand are called "virtual particles". I wouldn't think they have anything more to them than, say, the coefficients of a series development in classical perturbation theory.
Finally, Fadeev-Popov ghosts are also just a mathematical trick in order to fix a gauge in above said calculation. Consider them as something like lagrange parameters who are a trick to impose a boundary condition.
Nobody complains about the absence of physical meaning of a lagrange parameter, right ?

[*]Invisible extra dimensions. Curled up in weeny little balls they are; but in an earlier day any physicist whose theory told him the dimension of spacetime is 26 or 10 or whatever, would have abondoned it as a bad job.

This is indeed one of those things that are open. Might. Might not. As you point out, however, as long as there's no indication for it, why would it ?

[*]And lastly and very much leastly, the landscape. I don't think there is anything I could say about this abortion that some famous physicist hasn't said already.

Well, I don't see what's so terribly wrong with that, by itself. You have a class of potential theories, described by "a set of parameters", and experiment determines which values of the parameters are "right". It has always been that way, there's no reason why this should not be the case now.

Is it because picking a number in a continuous set of possible values sounds simpler than picking a specific point in a (big) discrete set ?
The silliest idea I ever heard was the idea of "unique only possible theory of everything". Weinberg already long ago told us why that's silly: "I don't see what's wrong with a classical world with hard spheres". So the set of "possible" universes already contains a classical world with hard spheres, and we know that it is not ours. So there are already at least TWO possible worlds and only empirical evidence tells us it is not the one with the spheres. So what's wrong with finding many more ? Only experiment can distinguish between all the possible products of the mind that *could* be possible worlds. Plato's multiverse is much bigger than our universe and there's only experiment to guide us.

So I repeat my argument:
The wrong turn has been, when experiment has been put aside and when theorists started thinking they could find a "theory of everything" purely based upon theoretical arguments. Back to the Greek armchair scientists.

 

[vanesch]

Physicsts have ALWAYS been reifiers. It goes back to the Stoic philosophers turning Appolonius and Ptolemy's epicycles and deferents into "crystal spheres" mysteriously interpenetrating. And you recall those nineteenth century winners, Caloric (reified heat) and the luminiferous ether. And Maxwell may have been a little kidding on the square with his cogwheel model of the EM field, but his friend Tait was dead serious about his vortices.

Well, they were right about that. If their theory told them there was a caloric fluid, they shouldn't start waving their hands about how one shouldn't take this seriously. However, it seems that many people think that "the ontology of a theory" is to be confused with "how the world really is". The "ontology of a theory" tells you what a THEORY TELLS YOU HOW THE WORLD LOOKS. It doesn't tell you how the real world looks like - something we'll never know for sure.
If you're thinking that you have a great theory, but "you shouldn't take its ontology seriously", then you're actually saying that you think that your theory is wrong ; and even so terribly wrong that it isn't even useful to think about the kind of world the theory talks about. Now, if theories are always to be falsified one day, then we can already with some solid confidence say that at any time in history or in the future, all theories we'll ever have, will turn out to be "wrong", in that they are based on the wrong principles, and present a wrong ontology.
But they'll be useful. And in order to understand *the theories* best, in order to devellop an intuition for them, it is a good idea to picture the toy world where they are right ; that's nothing else but an ontology of the theory. Chances are big that it has in the most remote sense nothing to do with our world (which we don't know and of which we will never know exactly how it is). After all, we might be characters in the dream of a deity.
It is very useful to think of the ontology a theory presents you to understand the theory. If you find the ontology crazy, then you should also find the theory crazy.

 

[arivero]

Euh, dreadful beasts ??! I have been repeatedly mentioning that experiment cannot even distinguish between these beautiful classical field theories and undefined quantum whatsoevers (they are not even theories yet). And I guess you are going to tell now that spin is not a continuous quantized variable ?

You were probably mentioning it, I am sorry I was not hearing. But OK, you guys have mentioned the possibility of a wrong turn there at Copenhagen, I have mentioned a even earlier one... but these posibilities are not under discussion here, because discoveries keep coming after these "turns". Rovelli ask how is that we are not getting more patterns of "prediction followed with discovery".

 

[Careful]

You were probably mentioning it, I am sorry I was not hearing. But OK, you guys have mentioned the possibility of a wrong turn there at Copenhagen, I have mentioned a even earlier one... but these posibilities are not under discussion here, because discoveries keep coming after these "turns". Rovelli ask how is that we are not getting more patterns of "prediction followed with discovery".

Well, I believe that ``Rovelli's question'' brings us back to alternatives to QM as I hinted above. Putting aside any ``rigor requirements'' it is true that the standard model had tremendous succes and the link between non-abelian gauge groups and renormalizability of the corresponding QFT is very suggestive. However, as Patrick has clearly argued U(1)*SU(2)*SU(3) is a phemenologically inspired model, there is nothing that suggests that non-abelian gauge groups somehow have a more fundamental place in physics. Actually, the failure in finding a GUT (read: grand unifying Lie (semi-simple) algebra) could very well indicate that it is not. Therefore, it is very important to look at the *known* experimental results in many different ways so that we can achieve an alternative understanding of the world. One of these alternatives *might* reflect a deeper underlying principle which is amenable to different applications than those for which it was orginally conceived. I do not believe that our contemporary theories allow for such extrapolation.

In other words, when experiment gives no further clues, then theorists might better clean up the existing theories as well as look for alternatives. This seems to be certainly more productive than looking for predictions of hypothetical theories which measure how many angels can sit on the head of a pin.

Careful

 

[vanesch]

In other words, when experiment gives no further clues, then theorists might better clean up the existing theories as well as look for alternatives. This seems to be certainly more productive than looking for predictions of hypothetical theories which measure how many angels can sit on the head of a pin.

Amen to that

 

[arivero]

However, as Patrick has clearly argued U(1)*SU(2)*SU(3) is a phemenologically inspired model, there is nothing that suggests that non-abelian gauge groups somehow have a more fundamental place in physics. Actually, the failure in finding a GUT (read: grand unifying Lie (semi-simple) algebra) could very well indicate that it is not.

Hmm note that Patrick argued recently

I don't think that it is purely an accidental thing.

There is something non-trivial about the fact that the standard model is renormalizable "in the old sense" (in the sense that all infinities can be reabsorbed into a finite number of parameters), as opposed to "renormalizable in the eft sense".

But it is true that the straight take on this principle has failed, in the sense that a GUT is already in the wrong alley (not predicting proton lifetime, etc). On other hand, the Call for Strings gets ground on the rejection of fundamentality of gauge groups and 4D Gauge QFT.

 

[Farsight]

I think particles were the wrong turn, before the standard model.

The Standard Model is the name given to the current theory of fundamental particles and how they interact. This theory includes Strong interactions due to the color charges of quarks and gluons, a combined theory of weak and electromagnetic interaction, known as electroweak theory, that introduces W and Z bosons as the carrier particles of weak processes, and photons as mediators to electromagnetic interactions.

They crop up everywhere, and colour so much thinking. Now I read something like the above and BANG I see the word particles, and I just shake my head. Then I see gluons and I shake my head some more. Strings are arguably better. But I wonder where we'd be if we'd stuck with Einstein's pure geometric "marble". At the risk of repetition, I was really surprised to find that Schroedinger said this in 1937:

"What we observe as material bodies and forces are nothing but shapes and variations in the structure of space. Particles are just schaumkommen. (appearances)". He believed that quantum waves were real, not probability distributions with a hidden particle wondering inside. He saw that abolishing the discrete point particle would remove the paradoxes of 'wave-particle duality' and the 'collapse of the wave function'...

 

[selfAdjoint]

Well, they were right about that. If their theory told them there was a caloric fluid, they shouldn't start waving their hands about how one shouldn't take this seriously. However, it seems that many people think that "the ontology of a theory" is to be confused with "how the world really is". The "ontology of a theory" tells you what a THEORY TELLS YOU HOW THE WORLD LOOKS. It doesn't tell you how the real world looks like - something we'll never know for sure.
If you're thinking that you have a great theory, but "you shouldn't take its ontology seriously", then you're actually saying that you think that your theory is wrong

Sorry, I just can't see this; it is for me "a distinction without a difference". If we can never know how the world is, then how does the ontology of a theory tell us anything at all about its quality? Maxwell's theory was an excellent one; his attempt to demonstrate an ontology for it was a blind alley. The equations themselves suggest no overarching ontology and support any nonce ontologies that experimenters or engineers find convenient.

What the search for an ontology of QM has shown me is that the projection is prior to the unitarity. Unitarity supports the unconscious tendency to reify the state vector, and is to some degree an assumption, constantly renewed by appeals to that reification. While the projection in all its naked puzzlement makes the real numbers that live in the real world.

 

[vanesch]

Sorry, I just can't see this; it is for me "a distinction without a difference". If we can never know how the world is, then how does the ontology of a theory tell us anything at all about its quality?

By guessing, and probably being wrong, of course :tongue: as is always the case for a fundamentally hypothetical concept such as "ontology".
Even if I don't know anything about fire-spitting dragons, I can tell stories about them to the kids. The concept of ontology itself is already hypothetical (given that solipsism is not falsifiable), so we're free to guess the way we like, no ?

Maxwell's theory was an excellent one; his attempt to demonstrate an ontology for it was a blind alley. The equations themselves suggest no overarching ontology and support any nonce ontologies that experimenters or engineers find convenient.

This is not entirely true. The electric and magnetic field in Maxwell are ontological. Leaving them out would hopelessly complicate the ontological picture that would emerge, where locality, causality and all that would be very dubious, while they are quite clean if we give an ontological status to the E and B field (in whatever representation: equivalence class of potentials, 2-tensor, separate E and B field ...). You are referring to re-interpreting them as mechanical displacements or anything, but that's not necessary. If you do Maxwell theory, the E and B fields (or another representation) take on a "real" character, and the theory is best understood if you think of the E and B field as "really there". It helps you understand the theory. It would not help your intuition about Maxwell theory if you always would remind yourself that "the E and B field are not really there, they are just a convenient mathematical way (an algorithm) to calculate the influence on this charge here, for the motion of all those charges there. You would not even be able to think of light beams and all that because a light beam would be an algorithm that helps you calculate how currents will move in a photodetector as a function of transitions in a far-away laser and motions of charges in dielectric media such as lenses. You couldn't even say that "a light pulse is propagating", or that a lens focusses the beam or anything. You'd simply have to say that all that is an algorithmic procedure to account for the composed influence (action-at-a-distance) of remote charges moving, on the observed currents or charges moving.
We see that by giving ontological status to the E/B field (or its variants), we do away with this complicated delayed-action-at-a-distance stuff, and understand that remote charges interact remotely with the field, that this field has an internal dynamics so that ripples in it propagate, and then these ripples are now interacting with charges here ; and that the charges here are not in any way constantly doing a bookkeeping of all movement in the past of all charges. They just interact locally with a genuinely existing field. So the obvious "ontology" of Maxwell theory is the postulate of the existence of a physical field.

The crazy things one wants people to believe in quantum theory by denying any ontology to the wavefunction is analogous to trying to do Maxwell theory without introducing the notion of electromagnetic field.

What the search for an ontology of QM has shown me is that the projection is prior to the unitarity. Unitarity supports the unconscious tendency to reify the state vector, and is to some degree an assumption, constantly renewed by appeals to that reification. While the projection in all its naked puzzlement makes the real numbers that live in the real world.

There is no more reification of the state vector, than there is reification of the E/B fields in Maxwell, or reification of matter points in Newton. These items are simply the basic ingredients of the theory at hand, so you have no choice but to say they are real, if you are proposing an ontology for the theory. You never complain about the reification of the concept of "Moon", which is just a convenient concept in an algorithm to compute visual impressions when looking at the sky, tidal effects, and sensory experiences of astronauts, right ? This is because the concept of "Moon" is such a simplifying concept in explaining all these experiences (tidal effects, light impressions when looking at the sky, feeling something like rock under moonboots,...) that it is a conceptually strongly simplifying idea to say that there really is a moon, and that this is not just an algorithmic concept that helps us organize all these sensations and experiences.
In the same way, it is simplifying to say that there really are atoms etc...
Well, in the same way, when doing quantum theory, it is conceptually simplifying to say that there really IS a wavefunction which does all these marvelous things, and that this is more than just an algorithmic concept that allows us to compute outcomes.

Ontology is nothing else but a simplifying hypothesis that helps us organize our experiences, and so, within quantum theory, the wavefunction plays such a central role that it must be ontologically accepted, until we may have a better (and different) theory.

As for projection, it is very well possible that projection is 'for real', but it will only be so in a theory that describes the precise dynamics of it, and this dynamics will have some non-locality to it. But quantum theory as we know it doesn't give us such a precise dynamical prescription, and so projection cannot really be part of the ontological prescription of quantum theory. So until we have a precise dynamical prescription (which would allow us to say when quantum interference is NOT to be expected, and hence to test this against experiment), it cannot be part of the ontology of quantum theory as we know it today.

 

[Farsight]

The crazy things one wants people to believe in quantum theory by denying any ontology to the wavefunction is analogous to trying to do Maxwell theory without introducing the notion of electromagnetic field.

Sounds good to me vanesch. But where does that leave particle physics?

 

[Mike2]

Ontology is nothing else but a simplifying hypothesis that helps us organize our experiences, and so, within quantum theory, the wavefunction plays such a central role that it must be ontologically accepted, until we may have a better (and different) theory.

The trouble is that the wavefunction is an ontological contradiction of terms: the square root of the probability that something might be here or there? Can we say that a probability is "real"? We say it is "real" when we measure it to be the case, but probabilities themselves are only an abstract thing that by difinition is not real in itself. But this sounds like a pretty old argument.

The best we can probably know is that there is a certain emount of information associated with things, even at the Plank scale. Then if we can connect geometry with the functions that tell us how much information is involved, then we might be able to develop an ontology associated with that geometry. We will never actually see the geometric shapes at that scale, but we may be able to gather the information stored in those objects.

 

[Farsight]

If the wavefunction is what's really there, and especially if we're talking about geometry, the moot question is: what objects?

 

[Dcase]

Logarithmic Spirals and spinors / twistors

This is a speculative answer:

Logarithmic Spirals and helices as geodesics and [with loops] as complex harmonic oscillators.

The imaginary unit may be responsible for the natural occurrence of Logarithmic Spirals [as in Nautilus] and vorteces [water drainage, various cyclones, solar system Parker‘s spiral and barred spiral galaxies] through the transcendental numbers Pi and e and the invisible but extant number i.

The "invisible" or "imaginary" object may be the "invisible" or "imaginary" elliptical locus in multiple body problems.

David Hestenes wrote the ‘The Kinematic Origin of Complex Wave Functions’ discussing Dirac and Schroedinger theories.
He describes circular and helical Zitterbewegung and trajectory of the electron, relating them to the “complex phase factor in the complex function” yielding a physical origin for these statistical properties..
[Hestenes like many uses h-bar which does simplify numeric calculations. However h better identifies the eccentricity.]
http://modelingnts.la.asu.edu/pdf/Kinematic.pdf

Caspar Wessel basically proved the existence of the ‘imaginary unit” in 1797. This entity is likely more invisible than imaginary and not a simply a mathematical construct.
‘An Imaginary Tale: The Story of i [the square root of minus one]’ by Paul J Nahin (Hardcover - 24 August 1998)

Consider this applet illustration from MathWorld, with the sun at one locus and nothing at the other locus except a calculation with respect to the influence of a large upon a small celestial body.
http://mathworld.wolfram.com/Ellipse.html

Logarithmic Spirals
a - MathWorld ‘Mice Problem’ applet
http://mathworld.wolfram.com/MiceProblem.html

b - Hermann Riecke and Alex Roxin in their ‘Rotating Convection in an Anisotropic System’ features images. http://www.esam.northwestern.edu/~riecke/research/Modrot/research_klias.htm

Other images:
a - NASA Cosmicopia, The Heliosphere, The Sun's Magnetic Field, the Parker spiral
http://helios.gsfc.nasa.gov/solarmag.html

b - NASA Astronomy Picture of the Day [Spiral Galaxy M83]
http://antwrp.gsfc.nasa.gov/apod/ap950912.html

 

[Farsight]

Spirals, vortexes, loops...

https://www.physicsforums.com/showthread.php?t=125354

...And I've got some reading to do.