Where we stand-Baez talk at Luminy

[f-h]

**I can do the same in LQG. **

- Of course you can.

Then what did you say I can not do in QG again? I thought your point was somehow that this amounted to unacceptable gaugefixing?

Yes when I say gaugeindependent in a fully constrained system that means frozen. Dittrichs observables are frozen observables on frozen states.

We started out talking about locality in Quantum mechanical systems without a background structure. So now you agree that in LQG I can play the same old relational space time scalar game.
This is of course one of the predecessors for (or a special case of) Rovellis game. You use a nongauginvariant quantity (the Rici scalar field) and relate it's value to another quantity that is nongaugeinvariant too in such a way that you get a gauge invariant quantity (Dittrich basically replays that game in the new language in her second paper on Observqbles in GR, and to my knowledge that is the first time the space time scalar game has actually been translated into real Dirac observables). Of course that's not the whole story since this does not reflect how we do real GR predictions. This is a chief concern, to make conceptionally clear how the actual predictions we make can be formulated in a background independent formalism.

*Matter information can be GENERICALLY retrieved from metric invariants.*

Are you talking about Kuchar's constructions now? Could you expand on this a bit?

---
What are you actually saying I can not do in LQG?
You made very general points about what is impossible in Quantum Gravity. I point out that in LQG I can do these things so I provide a counterexample to your initial claims of incompatibility, no?

Now you are saying that we don't have a good Quantum algebra, that the quantization of GR has only partially succeeded so far. Well I would have to agree since Thiemann says the same thing as well. But what has that to do with your initial claims that background independence and locality are incompatible in Quantum mechanics?

"So, it is quite obvious that you can abstractly look for gauge invariant statements." So if I can do that, and these have a local interpretation in an appropriate sense of the word local (as you seem to agree for spacetime scalars for example which Dittrich treats with the same methods), then there is no fundamental conceptional incompatibility between Background independence, locality and QM, right?

So then there is no reason to conclude that background independence as suggested by GR is a red herring Quantum mechanically.

 

[Careful]

**
- Of course you can.

Then what did you say I can not do in QG again? I thought your point was somehow that this amounted to unacceptable gaugefixing? **

Sorry, but I told you EXPLICITELY in my previous message what my DIRECT concerns are vis a vis your toy models. I explained you why this idea of how to construct local observables is LIMITED, no room for improvement any more. The lack of further unification possibilities leads to a pleithorea of physical states, so you will have to tell us why nature is so selective (a kind of initial value problem if you want to).


** We started out talking about locality in Quantum mechanical systems without a background structure. So now you agree that in LQG I can play the same old relational space time scalar game. **

Sure, but you did at the same time not make any effort to dig deeper into the measurement problem either. But you still do not understand here what I am telling you.

**
This is of course one of the predecessors for (or a special case of) Rovellis game. You use a nongauginvariant quantity (the Rici scalar field) and relate it's value to another quantity that is nongaugeinvariant too in such a way that you get a gauge invariant quantity (Dittrich basically replays that game in the new language in her second paper on Observqbles in GR, and to my knowledge that is the first time the space time scalar game has actually been translated into real Dirac observables).**

Yes and no, I told you in the beginning already that some old knowledge was rewritten into the ADM framework. No, because if you add sufficiently many invariants then you can give an event a diffeomorphism invariant meaning even if you would naively expect the diffeo's to shift the point around in the manifold. You are still not fully comprehending the magnitude of how far you can gow with this idea.


** Of course that's not the whole story since this does not reflect how we do real GR predictions. This is a chief concern, to make conceptionally clear how the actual predictions we make can be formulated in a background independent formalism. **

Very simple, take ONE point with physical coordinates (a,b,c,d) and call that ``I now´´. The worldline will be generically determined by the dynamics and we can make observations like we do them with sattelites and so on. ADDENDUM : of course you might say : well, we need to say where in the four manifold *all* people are alive, so we need a kinematical gauge to do that. You might do that in this way, but I have pointed out on the philosophy forum once that you can also choose phyiscal globally defined ``lifetime´´ functions to achieve that. Moreover in *classical* GR any such construction is NOT changing anything to the way we observe the universe, this still happens by sending/recieving signals from distant galaxies (the lifetime function being more like a philosophical completion of GR). However in QM, this DOES change the physics in the sense that it provides a natural basis for defining entanglement. It *changes* the phyiscs because entanglement gives you non-local correlations which CANNOT be explained by local mechanisms unless you add ghost fields which violate causality or so. People usually think that they did nothing wrong because entanglement is just ``kinematical´´ : that is how dangerous empty words can be.

**
*Matter information can be GENERICALLY retrieved from metric invariants.*

Are you talking about Kuchar's constructions now? Could you expand on this a bit? **

Just read about the genericity conditions for spacetimes, I do not remember if it was Kuchar in particular, Bergmann, Ehlers and others have done a lot of work on constructing many different ways to interpret GR just on basis of the metric (and light signals).

**
---
What are you actually saying I can not do in LQG?
You made very general points about what is impossible in Quantum Gravity. **

The general point I make about *background independent* quantum gravity is that in principle NO further unification between matter and geometry is possible (the way I argued about this is indeed through the very notion of local observable). Moreover, since you still work with the metric field as dynamical variable, I am afraid that you won't come to a satisfying unification with electromagnetism either. En plus, you do not change anything substantial to QFT and neither to GR, so I do not see why you should solve the cosmological constant unless you can somehow kill off the vacuumenergy in QFT by a natural mechanism.

**
I point out that in LQG I can do these things so I provide a counterexample to your initial claims of incompatibility, no? **

You still do not understand that I was trying YOU to DEDUCE that these ideas are all quite limited and produce an extreme high number of degrees of freedom.

**
Now you are saying that we don't have a good Quantum algebra, that the quantization of GR has only partially succeeded so far. Well I would have to agree since Thiemann says the same thing as well. But what has that to do with your initial claims that background independence and locality are incompatible in Quantum mechanics? **

Ahhhhrrrr, I explained you already that background independence and locality are not incompatible PROVISO that you do not care about solving other problems floating around. And it is silly to agree with me because Thiemann says the same, perhaps we are both demented (who knows ?? )

**
So then there is no reason to conclude that background independence as suggested by GR is a red herring Quantum mechanically. **

I just said that to you in the beginning hoping that you would try to look for something else (but no, just defensively shutting down).

My main concern about all this business is that - apart from the very scarse ``progress´´ which has been made in the last 20 years - there is a very sharp *small* possibility for further improvements to be made. I tried to make you see a glimpse of that by going over to a construction where matter would be ``geometrical exitations´´ but it seems I failed miserably (I still underestimate the defensive reflex of people).

By the way, Smolin seems bend over to the geometry as an observable of an interacting matter ensemble too, but of course still has to say that you can do this topologically (in either background independent). That is where I disagree and I have offered a series of arguments why you can expect a background to be necessary in the case of matter from geometry.

Cheers,

Careful

 

[Careful]

To wrap up: the very limited goals set up by LQG and similar approaches are a weakness since other theories outside QM and GR (say EM) are making us aware that something else is happening (I have pointed this out several times in my posts) - at least when you *really* try to unify them. So, even in the event one will succeed in finishing LQG or whatever spin foam in a natural way at some point in time (and everything points into the direction that this is unlikely), then still have you constructed a theory which is too narrow if you want to do a good job incoorporating other forces. That is a good reason why one should look for new physics, no ??

Cheers,

Careful

 

[jarek]

FYI: I´m nowhere even close to orthomodular guys , I don't even know any in person

Here are the Aharonov papers:

IS THE USUAL NOTION OF TIME EVOLUTION ADEQUATE FOR QUANTUM-MECHANICAL SYSTEMS .1.
PHYSICAL REVIEW D 29 (2): 223-227 1984

IS THE USUAL NOTION OF TIME EVOLUTION ADEQUATE FOR QUANTUM-MECHANICAL SYSTEMS .2. RELATIVISTIC CONSIDERATIONS
PHYSICAL REVIEW D 29 (2): 228-234 1984

I like the second one much more Anyone aware if his description of evolution in QM (surfaces rather than time parameter, much like ADM) has been further developed?

Cheers,
j

 

[Careful]

**FYI: I´m nowhere even close to orthomodular guys , I don't even know any in person **

My sincere apologies ()

**
Here are the Aharonov papers:

IS THE USUAL NOTION OF TIME EVOLUTION ADEQUATE FOR QUANTUM-MECHANICAL SYSTEMS .1.
PHYSICAL REVIEW D 29 (2): 223-227 1984

IS THE USUAL NOTION OF TIME EVOLUTION ADEQUATE FOR QUANTUM-MECHANICAL SYSTEMS .2. RELATIVISTIC CONSIDERATIONS
PHYSICAL REVIEW D 29 (2): 228-234 1984

**

Thanks, I will certainly take a look at it.

Cheers,

Careful

 

[CarlB]

I explained you why this idea of how to construct local observables is LIMITED, no room for improvement any more. The lack of further unification possibilities leads to a pleithorea of physical states, so you will have to tell us why nature is so selective (a kind of initial value problem if you want to).

I think that this is the heart of the matter. If I understand you, in terms of QFT, it boils down to the Coleman-Mandula theorems. If so, I would like to point out that these theorems assume perfect Poincare symmetry, and if an underlying theory violates this, it will allow more possibilities for unification.

In particular, the Koide mass formula is pretty good evidence that there is a unification out there:

The strange formula of Dr. Koide
Alejandro Rivero, Andre Gsponer
We present a short historical and bibliographical review of the lepton mass formula of Yoshio Koide, as well as some speculations on its extensions to quark and neutrino masses, and its possible relations to more recent theoretical developments.
http://www.arxiv.org/abs/hep-ph/0505220

For a list of the problems that the above formula gives to the standard model, and also to the usual ways of unification, see Dr. Koide's comments here:

Challenge to the Mystery of the Charged Lepton Mass Formula
Yoshio Koide
Why the charged lepton mass formula m_e +m_\mu +m_\tau = 2/3\; (\sqrt{m_e}+\sqrt{m_\mu} +\sqrt{m_\tau})^2 is mysterious is reviewed, and guiding principles to solve the mystery are presented. According to the principles, an example of such a mass generation mechanism is proposed, where the origin of the mass spectrum is attributed not to the structure of the Yukawa coupling constants, but to a structure of vacuum expectation values of flavor-triplet scalars under Z_4 \times S_3 symmetries.
http://www.arxiv.org/abs/hep-ph/0506247

Carl

 

[arivero]

I think that this is the heart of the matter. If I understand you, in terms of QFT, it boils down to the Coleman-Mandula theorems.

And to the puzzling detail of CKM mixing between generations; I still do not understand fully how the mixing can happen under Coleman-Mandula conditions; the whole electroweak group should commute with Poincare, and the mass eigenstates should be charge eigenstates too, shouln't?

 

[CarlB]

And to the puzzling detail of CKM mixing between generations; I still do not understand fully how the mixing can happen under Coleman-Mandula conditions; the whole electroweak group should commute with Poincare, and the mass eigenstates should be charge eigenstates too, shouln't?

This smells very much like the windmill what JC Yoon has been tilting at recently. Well the holy grail on which I'm "working", though I really don't know how to do it, is to get the MNS matrix into the same form as the Koide mass formula. There is a bit of a hint by JC Yoon that I do not understand. Wish I did. I put comment #6 here on the question of whether the CKM / MNS matrices imply that charge is not conserved:

https://www.physicsforums.com/showthread.php?t=106583

My guess is that if you argued that Coleman Mandula was contrary to mixing angles, the response would be identical to the response JC Yoon got when he claimed that the standard model is not perfectly Lorentz symmetric. That is:
https://www.physicsforums.com/showthread.php?t=108277

Carl

 

[arivero]

Well I have no problem with the Standard Model; the Lagrangian of the Standard Model does not have mass terms, all the particles are nicely massless. Masive particles are incompatible with Nonabelian Gauge fields, we are taught in the kindergarten.

But I have a respect for Wigner classification scheme and Coleman-Mandula theorem (nice and short paper, btw) so I wonder what happens when particles get mass and must transmute from the massless to massive representations.

 

[marcus]

To get back to the initial post on this thread

a simple rather beautiful talk

http://math.ucr.edu/home/baez/where_we_stand/mentioned in yesterday's TWF #227
http://math.ucr.edu/home/baez/week227.html

Here is my take on it: what I think the talk by Baez at Luminy means.
Luminy and Perimeter are the two capitals of LQG, Baez was talking to the LQG community plus a wider audience.

LQG is beginning to strive for a background independent unified theory that should explain dynamical geometry AND matter.

Baez was saying something simple and possibly profound. namely he says look at these mysteries

black hole
dark matter
cosmological constant
curious neutrino behavior
messiness of the standard model

He is saying, I think, that one should find a fundamental QG theory that
explains dark matter, consmological constant, what happens inside black holes, neutrino astonomy observations, and simplifies the standard model.

He was suggesting, I think, that if one could find the fundamental degrees of freedom describing dynamical geometry that could also very likely turn out to describe matter. Such a theory could, I think, be local because matter defines locality

a place ultimately is always referred to a material event or object----a tabletop, a rock, a tree, a measuring machine. Baez does not mention locality in his talk, but I think he is evoking the idea of a unified theory (unifying matter and geometry) and such a theory has matter to establish place.

Baez paper that he released about the same time as he posted his "where we stand---fundamental physics" talk has an essentially TOPOLOGICAL character.
It is about 4D beef theory. Where matter is discovered as some topological tangles in the beef.

there are some microscopic defects in the spacetime that create the snarly-gnarly of matter----stuff in the geometry that doesn't go away easily.

That is enough, or already too much, to say about the new Baez paper on "4D BF theory" but it does provide a little context for "where we stand" because they appeared about the same time.

Here's the 4D beef paper.
http://arxiv.org/abs/gr-qc/0603085
Here is one of the PF threads about it
https://www.physicsforums.com/showthread.php?p=945369#post945369

 

[marcus]

I think if we really want to have a discussion in this thread, which is actually a discussion of Baez "where we stand" Fundamental Physics talk, then we need to begin by looking at the SIX MYSTERIES that form the backbone of his talk.

http://math.ucr.edu/home/baez/where_we_stand/where_we_stand.pdf

I think LQG is entering a new stage where it strives to provide a unified theory (of spacetime and matter) and if it can explain matter then for example it should be able to explain MASS which is closely connected to the geometry of spacetime. This is one of Baez 6 mysteries.

I will quote the mysteries and also, in parens, comments he makes in between to help make them understandable:

===quote Baez===
Mystery 1. What is making the expansion of the universe accelerate? Does the vacuum have negative pressure?

Mystery 2. Does the Higgs really exist? What is the origin of mass?

Mystery 3. Why do these 18 numbers have the values they do? ...(Where can we find defects in the Standard Model? In the heavens.)

Mystery 4. Do neutrino oscillations fit into a slightly modified Standard Model – now requiring 25 dimensionless numbers – or must the theory be changed more drastically?

Mystery 5. What happens to things when they fall into a black hole?

(... there are not enough stars to explain the mass of the Virgo Supercluster! This ‘missing mass problem’ is also evident in other ways:
• Galaxies rotate faster than can be explained by all understood forms of mass.
• Our theories of galaxy formation don’t work without positing ‘cold dark matter’.
• Fluctuations in the microwave background radiation fit a model with cold dark matter, not a model without. We need at least 5 times more cold dark matter than normal matter! Or perhaps something more radical: e.g., general relativity is wrong.)

Mystery 6. What is cold dark matter – or what else explains what this hypothesis tries to explain?

(...But meanwhile, experiments and observations continue, showing that we live in a universe that is far from understood, even at the simple level of fundamental physics. This is not bad. It merely leaves more fun for our children and grandchildren. . . if we leave them a world in which they can afford to study such questions.)

===end quote===

 

[Careful]

Everyone in physics knows these questions.

**
He was suggesting, I think, that if one could find the fundamental degrees of freedom describing dynamical geometry that could also very likely turn out to describe matter. Such a theory could, I think, be local because matter defines locality **

The problem which such line of thinking is the *enormous* amount of freedom in the number of states the universe can be in (by the way, I argued that such line of thinking will always involve a kind of ``preferred geometry´´). Basically, you still have to tell which piece of spacetime 1 corresponds to which piece of spacetime 2 and so on - complete freedom in such choice introduces ambiguities growing faster than n! where n is the number of ``events´´ in your spacetime. So, by this kinematical labelling procedure you can retrieve ``locality´´ - this is an old story, say in causal sets (where people really try to do better than that and still use Minkowski as reference background ). You know, it is possible to repair just any shortcoming by increasing the number of degrees of freedom in your construction - that is an ancient trick. It is just that by doing this, you are simply ignoring the fact that you did not understand at all what is going on (even worse: success in such approach might even convince you that this was the right path - that is what happened with quantum mechanics). Moreover, any such theory is far removed from LQG which is still more or less directly ``quantized gravity´´.

**
a place ultimately is always referred to a material event or object----a tabletop, a rock, a tree, a measuring machine. Baez does not mention locality in his talk, but I think he is evoking the idea of a unified theory (unifying matter and geometry) and such a theory has matter to establish place. **

Sure, that is what we do in practice, but the question is whether the theory can do this in a elegant and minimalistic manner.

**
Baez paper that he released about the same time as he posted his "where we stand---fundamental physics" talk has an essentially TOPOLOGICAL character.
It is about 4D beef theory. Where matter is discovered as some topological tangles in the beef. **

That is possible in principle but *extremely* difficult. Causal sets is trying to do this for about 20 years now and the lesson to be learned from this is the following: one is only still at the very beginning in understanding how to characterize dynamical geometry without reference to the continuum. Now, you might say : ``ah but this is beautiful, plenty of open problems for the future generation´´. I would agree with this if the benifit would be a better understanding of quantum mechanics and the measurement problem : I mean if you want to go that far in constructing a theory which is unlikely to give any substantial predictions in 50 years, then you better make sure it is worthwhile, no ? I can only observe that one is still looking for a right formulation of ``quantum´´ in that context, so also causal set researchers do not really know very well how to deal with QM.

The painful contradiction in this story is that really fundamental research in QM is frowned upon and almost forbidden; so far your liberty in academics

Cheers,

Careful

 

[marcus]

The painful contradiction in this story is that really fundamental research in QM is frowned upon and almost forbidden; so far your liberty in academics

Cheers,

Careful

You sound very disappointed, Careful. Have you tried yourself to do really fundamental research in QM and found this by your own experience that it is not approved?

 

[marcus]

I think if we really want to have a discussion in this thread, which is actually a discussion of Baez "where we stand" Fundamental Physics talk, then we need to begin by looking at the SIX MYSTERIES that form the backbone of his talk.

http://math.ucr.edu/home/baez/where_we_stand/where_we_stand.pdf

I think LQG is entering a new stage where it strives to provide a unified theory (of spacetime and matter) and if it can explain matter then for example it should be able to explain MASS which is closely connected to the geometry of spacetime. This is one of Baez 6 mysteries...

for continuity, here are the 6 mysteries Baez mentioned, in condensed paraphrase:

Mystery 1. Acceleration? (What dark energy is supposed to explain)

Mystery 2. Mass? (Inertia and gravitational mass: the interaction between matter and spacetime)

Mystery 3. Model parameters. (Why these particular numbers?)

Mystery 4. Neutrino oscillations?

Mystery 5. Black holes. (What happens to things? The infall.)

Mystery 6. Missing mass? (Explain what cold dark matter was invented to explain...or else say what it is.)


(Baez comment about #6... there are not enough stars to explain the mass of the Virgo Supercluster! This ‘missing mass problem’ is also evident in other ways:
• Galaxies rotate faster than can be explained by all understood forms of mass.
• Our theories of galaxy formation don’t work without positing ‘cold dark matter’.
• Fluctuations in the microwave background radiation fit a model with cold dark matter, not a model without. We need at least 5 times more cold dark matter than normal matter! Or perhaps something more radical: e.g., general relativity is wrong.)

======================

Baez new paper "4D BF theory" suggests that matter is made of the same stuff as space. Figuratively, matter is just the tangles in it.
And time is a homotopy.

This is clearly inviting bids for a unified theory. And it is not an isolated instance. there are papers not just by Baez Wise and Cran but also by Oriti and Ryan, Krasnov, Freidel, Livine, Smolin, Sundance, Starodubstev and so on.

So by all appearances it looks like the LQG community is getting ready for a push for some unified theories.

And a unified theory (a theory of space time and matter) ought to address some of Baez six puzzlesSO HERE WE HAVE THE TOPIC of the thread in the form of a nice DEBATE ISSUE. Some people will immediately want to give reasons they have thought up of why IT WILL NEVER WORK and why whatever the LQG community comes up with along the lines of these recent papers is bound to FAIL. Or they say it is a waste of taxpayer money, or they say they know the only right way to approach the problem but nobody will listen to them.

And the other side of the debate is YES IT MIGHT FAIL but it is only a few people--- the LQG people are a small research community with at most a few dozens active in this line---and it is a very SMALL EXPENSE of taxpayer money---and it MIGHT SUCCEED. They might actually get closer to a new understanding of spacetime and matter!

=============================

here's another PF thread discussing the direction LQG is going with links to some recent papers
https://www.physicsforums.com/showthread.php?t=115289

 

[Careful]

You sound very disappointed, Careful. Have you tried yourself to do really fundamental research in QM and found this by your own experience that it is not approved?

Fundamental research in QM only gets accepted:
(a) when your name is 't Hooft, Biley, ... or when you are directly ``protected´´ by them either in the sense that you work together with one of those people, or you are working on 't Hooft quantum mechanics.
(b) when you elaboratly confirm in the first 2 pages of your paper how great quantum mechanics is, that it was the most supreme human intellectual achievement of all times
(c) when you explicitely mention in your paper that it is merely your intention to humbly probe deeper into the conceptual framework of QM
(d) depending on whether (a) is satisfied or not, people will ask you to present a solution for ALL well known problems at once (in one paper).

Of course, Marcus I am intensively working on QM (I am a persistent person when I found something *worthwile* to do). Obviously, my ideas shifted already a great deal since I started doing this, they got entirely classical. I am actually still shocked that most physicists take Bell's theorem seriously, it is so easy to bypass it while still securing Lorentz invariance in the necessary way. You have no idea how religious rational people can be about their pet theory.

Cheers,

Careful

 

[Careful]

**
SO HERE WE HAVE THE TOPIC of the thread in the form of a nice DEBATE ISSUE. Some people will immediately want to give reasons they have thought up of why IT WILL NEVER WORK and why whatever the LQG community comes up with along the lines of these recent papers is bound to FAIL. **

Well marcus, that is an essential part of the debate, no ?? You simply seem to forget that these objections require answers (the critics are usually not stupid you know). The key issue in these presumed ``background independent´´ approaches is LOCALITY. The ``solutions´´ presented by the LQG community are well known for a few decades and do no not contribute really to our understanding. They merely replace the locality problem for the question why God placed his pin into the enormous landscape of possibilities in order to generate our universe (by the way, this does not mean yet that the locality problem is solved - the right dynamics still has to decide about that.). Moreover, locality or not, there are plenty of ambiguities left in LQG - the quantization of the Hamiltonian constraint seems to be plagued by that already. BTW, that is exactly the reason why I boldly state that locality has not been solved: I do not like pseudo solutions.

** And the other side of the debate is YES IT MIGHT FAIL but it is only a few people--- the LQG people are a small research community with at most a few dozens active in this line---and it is a very SMALL EXPENSE of taxpayer money---and it MIGHT SUCCEED. They might actually get closer to a new understanding of spacetime and matter! **

No, they actually did not. What you are presenting now (matter from geometry) has little or nothing to do with what has been tried out between 1985 and 2000 when people were rather exclusively looking for a quantum version of the constraint algebra (because that was matter + geometry) and spin networks were known from the days Penrose launched them (around 1975 I guess). By the way, I think Hossi also asked you why this should be only part of the LQG community, there are plenty of other less problematic approaches which can account for that.

Cheers,

Careful

 

[marcus]

The painful contradiction in this story is that really fundamental research in QM is frowned upon and almost forbidden; so far your liberty in academics

Cheers,

Careful

You sound very disappointed, Careful. Have you tried yourself to do really fundamental research in QM and found this by your own experience that it is not approved?

Fundamental research in QM only gets accepted:
(a) when your name is 't Hooft, Biley, ... or when you are directly ``protected´´ by them either in the sense that you work together with one of those people, or you are working on 't Hooft quantum mechanics.
(b) when you elaboratly confirm in the first 2 pages of your paper how great quantum mechanics is, that it was the most supreme human intellectual achievement of all times
(c) when you explicitely mention in your paper that it is merely your intention to humbly probe deeper into the conceptual framework of QM
(d) depending on whether (a) is satisfied or not, people will ask you to present a solution for ALL well known problems at once (in one paper).

Of course, Marcus I am intensively working on QM (I am a persistent person when I found something *worthwile* to do). Obviously, my ideas shifted already a great deal since I started doing this, they got entirely classical. I am actually still shocked that most physicists take Bell's theorem seriously, it is so easy to bypass it while still securing Lorentz invariance in the necessary way. You have no idea how religious rational people can be about their pet theory.

Cheers,

Careful

I wish you would give us links to your arXiv articles, so we can sample some of your research

 

[f-h]

*people will ask you to present a solution for ALL well known problems at once (in one paper).*

It's of course perfectly reasonable to expect the same from the LQG community with respect to the tricky conceptional issues involved. ;)

 

[Careful]

*people will ask you to present a solution for ALL well known problems at once (in one paper).*

It's of course perfectly reasonable to expect the same from the LQG community with respect to the tricky conceptional issues involved. ;)

No, there is a very distinct difference you know. If you manage to find a deeper realist theory behind quantum mechanics then many fundamental problems are solved at once, especially the conceptual ones. BTW: the LQG community already had 20 years to ``settle´´ the conceptual issues in a proper way - fundamental research into QM only revived very recently by very few people. I have the impression that researchers somehow got the idea that conceptual issues will be magically solved if enough technical progress is made (in the wrong conceptual framework).

I will spell out the details behind my own ideas on a realist QM in proper time (as I promised before + I mentioned this will take still around two months). For now, my only intention is to try to convey to you (marcus) that a physical theory usually starts out from a very clear conceptual picture (of the mechanisms at hand); then and only then the technical aspects follow. My conclusion in this game is that a thorough reformulation of QM and GR are necessary in order to restore the conceptual picture and that these problems are certainly *not* going to be solved by playing around with toy models. There is nothing wrong or negative when I present some of my arguments why I think LQG will not succeed in that in a satisfactory way: it is up to you to respond to them.

Cheers,

Careful

 

[marcus]

Careful what I would like from you is an arxiv link to one or several of your research papers, please. You have made your own research rejection by academia an issue. I want to know what it is.

I don't especially want to discuss the way that scientific theories are supposed to develop (whether from initially playing around with toy models or NOT doing that) in this thread.

I think of LQG as what the people in the LQG research community do---several lines of investigation in progress and shifting----I am not quite sure what your definition is, or how relevant your discussion of it is to this thread.

the topic of this thread is Baez talk on the current situation in fundamental physics and looking ahead----the role of research pursued by the LQG people at Luminy is also relevant since Baez was addressing those people, he knows their research, and he has just brought out a 4D BF theory paper himself at about the same time. (4D BF is one of those things being studied under the general rubric of LQG these days, as per the Freidel Starodubstev paper last year---yes I know putting BF with LQG is untidy, active research is not arranged in neat logical compartments)

 

[CarlB]

(d) depending on whether (a) is satisfied or not, people will ask you to present a solution for ALL well known problems at once (in one paper).

An example of this would be someone having you explain what "measurement" means when the standard model clearly doesn't have a clue.

Carl

 

[Careful]

**Careful what I would like from you is an arxiv link to one or several of your research papers, please. You have made your own research rejection by academia an issue. I want to know what it is. **

Oh no, Marcus I did not make that an issue at all : my background (as a person) here is entirely unimportant (and many of my papers were well received actually), let's stick to the content right ? I thought on this forum we can discuss physics and not be merely royalty watchers. When I spoke about realist papers I did not speak about myself in the first place. I am offering some specific general discussion points about background independent approaches and I get no response from you on these concrete fundamental issues.

**
the topic of this thread is Baez talk on the current situation in fundamental physics and looking ahead **

So, that means we can speak about fundamental issues in physics, no? Good, you don't like what I say, so please argue. In case you find yourself unable to do so, then we indeed better quit this discussion which has clearly no use then. For a change, can I ask you why you are so LQG oriented, you clearly are not aware of the details of many works, so how can you so confidently defend it ? Because you simply don't like the monopoly of string theory and you are in for some alternative ideas ?

Cheers,

Careful

 

[Careful]

An example of this would be someone having you explain what "measurement" means when the standard model clearly doesn't have a clue.

Carl

You got it

 

[marcus]

The painful contradiction in this story is that really fundamental research in QM is frowned upon and almost forbidden; so far your liberty in academics

Cheers,

Careful

You sound very disappointed, Careful. Have you tried yourself to do really fundamental research in QM and found this by your own experience that it is not approved?

Fundamental research in QM only gets accepted:
(a) when your name is 't Hooft, Biley, ... or when you are directly ``protected´´ by them either in the sense that you work together with one of those people, or you are working on 't Hooft quantum mechanics.
(b) when you elaboratly confirm in the first 2 pages of your paper how great quantum mechanics is, that it was the most supreme human intellectual achievement of all times
(c) when you explicitely mention in your paper that it is merely your intention to humbly probe deeper into the conceptual framework of QM
(d) depending on whether (a) is satisfied or not, people will ask you to present a solution for ALL well known problems at once (in one paper).

Of course, Marcus I am intensively working on QM (I am a persistent person when I found something *worthwile* to do). Obviously, my ideas shifted already a great deal since I started doing this, they got entirely classical. I am actually still shocked that most physicists take Bell's theorem seriously, it is so easy to bypass it while still securing Lorentz invariance in the necessary way. You have no idea how religious rational people can be about their pet theory.

Cheers,

Careful

I have to repeat. Your apparent disatisfaction with the reception of your research is an issue. You have raised the business of academic freedom and suppression of approaches that arent somebody's (like 't Hooft's) pets. and you keep suggesting that you have the right approach and that whatever the QG community at large is pursuing is doomed to fail. It is too obvious that if your ideas can't be accepted then everybody else has to be wrong.

You clearly have an ax to grind. So show us the ax.
Show us the research which is presumably on the right track---since you act like you've shown all these other people to be on the wrong track.

All the time you have been here at PF there is only one person that I can remember whose research you have approved----it is Johan Noldus. Since I don't have your papers, I will use his as an example.

IIRC it was in the "List of new initiatives" thread, I will get the link. Your approval even in this case was very lukewarm, I must say. I would like to have a sample of your own, but lacking that I will go fetch some that I recall your speaking positively about.

================
here we are

https://www.physicsforums.com/showthread.php?p=852574#post852574

Now I see that this PF forum can actually sometimes serve as an OUTLAW CAFE in some of its threads. We can help compensate for deficiencies in the system.
...
...
6. Johan Noldus (just noticed)

http://arxiv.org/abs/gr-qc/0508104
Towards a fully consistent relativistic quantum mechanics and a change of perspective on quantum gravity
17 pages, submitted to CQG

"This paper can be seen as an exercise in how to adapt quantum mechanics from a strict relativistic perspective while being respectful and critical towards the experimental achievements of the contemporary theory. The result is a fully observer independent relativistic quantum mechanics for N particle systems without tachyonic solutions. A remaining worry for the moment is Bell's theorem."can anyone express why we should dismiss the ideas of ... Noldus? Or, conversely, does anyone LIKE what [he has] to say and find it interesting?

... In the paper of Noldus, it is never claimed that there is a new approach to quantum gravity, actually many physicists have gone along the same path before him. The author simply wants to investigate what can happen to quantum mechanics when you consistently apply the principle of general covariance and the reality assumption that all processes describing the outcome of an experiment are real and happen in spacetime (although the latter is not explicitly stated, it is clear from the context). Therefore, if you do not dispose of the wave function, you need to attach a reality to it (the author sees measurement as part of that same physical process, so no U/R split). Assuming this, he basically comes to some form of the self field approach to quantum mechanics, which was derived by other means previously by A.O. Barut and J.P. Dowling and is known not to give the correct predictions (although the know differences are rather small, within a bound of 5%), as the author clearly states. Logically, in such a viewpoint, the author is forced to revise the theory of spin (see it really as a spinning particle) which, as he claims, is not excluded to be possible within the framework of of classical Einstein Maxwell theory (and he provides a nice reference which indeed suggests this). So, the question is now, what next? The author seems even to want to go further and see the wavefunction itself as an effective description of a classical chaotic locally causal process (i.e. the wave function is a thermodynamical ``averaged´´ description of a chaotic, locally causal, deterministic process. The locally causal aspect of this approach (which is somehow suggested by its spacetime character) IS the DARING aspect of this approach since it requires that no perfect Bell experiment is ever to be performed. However, IMO, a Bell test which kills off local realism, does not need to kill off such approach; one might consider adding nonlocality scales at that moment in time.

To wrap up: this paper is just (as said in the abstract) the report of an exercise made by the author. Most physicists who think about QM for some while write a paper about it (however, most of these papers are boring and simply discussing some personal ontological viewpoints). It remains to be seen what comes next (and that will be the real test).

even here you are not very generous with your approval, Careful. But in the next you seem to warm up some:
https://www.physicsforums.com/showthread.php?t=103750

This last link here is the closest thing to praise from you of someone's research that I have seen.
If you think everybody else work is so hopeless (and to me your arguments seem forced, as if by a need to show it) then I would really like to see what you do yourself.

 

[Kea]

My, my, haven't we all been busy? First, please permit me to define a few broad terms, as I believe they are commonly used.

Quantum Gravity: a very loose term meaning any theory capable of completely reproducing computational SM plus GR. This, of course, rules out conventional Strings, LQG and a large number of other proposals.

Background Independent: a property of a physical theory or model that must incorporate (1) independence of spacetime coordinates, and (2) a lack of any form of aether. This second condition is far more stringent. Even GR fails this test.

Logic: a not-necessarily-classical use of syntax with accompanying semantics involving truth-valued propositions and operations such as AND, OR, NOT, implication and quantifiers.

(Local) Observable: a mathematical construct representing the semantics of measurable numerical quantities. Clearly any theory that does not address the problem of measurement cannot hope to have a complete description of such operators.

Magic: entertainment involving well-trained tigers, hoops, mirrors, saws and people in shiny costumes.

In response to a couple of Careful's comments:

Moreover, I have given a LOGICAL reason why defining local
observables within a *background independent* quantum universe is IMPOSSIBLE.

Not according to the definitions that I have given above. You have been using a more restrictive set of definitions, in response to the comments of others, but some readers reasonably appear to be finding this loose use of terms confusing.

But the no-go argument *precisely* consists in asserting that ANY definition of a local observable REQUIRES extra relational information of the type mentioned above. If you do not specify any further information then you are bound to limit yourself to global observables such as average volume, dimension and so on, in either then you need to see the entire universe as a black box or you have to kill off superposition.

I think I more or less or agree, although you have not been clear, but the fact that QM needs alteration does not necessarily mean that we need to throw QM intuition out the window. I wonder if it has occurred to you that your conclusions re the necessity of a classical direction here might in fact be wrong. The alternatives involve enlarging one's sphere of logic - seemingly dire perhaps - but alternatives in the spirit of QM all the same.

Bernard d'Espagnat has written some rather severe comments
upon the conceptual difficulties quantum statistics faces in light of the measurement problem (I do not remember that well anymore)

An article I like by d'Espagnat is Quantum logic and non-separability in the volume The Physicist's Conception of Nature, edited by Mehra for Dirac's 70th birthday.

 

[Careful]

** You have raised the business of academic freedom and suppression of approaches that arent somebody's (like 't Hooft's) pets. and you keep suggesting that you have the right approach and that whatever the QG community at large is pursuing is doomed to fail. It is too obvious that if your ideas can't be accepted then everybody else has to be wrong. **

Ah marcus, you clearly did not understand how research works. When you are a young researcher who wishes to really solve conceptual problems, you have to sidestep for some amount of time with the consequence that one stops publishing. Those who do publish, are very much aware of these shortcomings I raised too (otherwise you do not deserve PhD in front of your name), they merely content themselves with the knowledge that one of their future heroes will solve it.

**
All the time you have been here at PF there is only one person that I can remember whose research you have approved----it is Johan Noldus. Since I don't have your papers, I will use his as an example.
IIRC it was in the "List of new initiatives" thread, I will get the link. Your approval even in this case was very lukewarm, I must say. **

Well, clearly this guy was only at the beginning of adressing the conceptual flukes in QM at that time - the retour to realism does not necessarily imply a negation of the Bell tests.

**If you think everybody else work is so hopeless (and to me your arguments seem forced, as if by a need to show it) then I would really like to see what you do yourself. **

As I said, career safety desicions often inforce a more or less conventional research topic upon you - unless you work in a math institute, then you basically can commit a reasonable amount of heresy. Your hero smolin has also adressed this problem several times.

But, again, tell me why you are such a LQG believer ??

Cheers,

Careful

 

[f-h]

Welcome to the fry. ;)

Background Independent: a property of a physical theory or model that must incorporate (1) independence of spacetime coordinates, and (2) a lack of any form of aether. This second condition is far more stringent. Even GR fails this test.

What do you mean by aether? Especially in the context of classical GR? All LQG people I know seem to consider classical GR to be BI. So your definition seems to be stricter then general usage.

(Local) Observable: a mathematical construct representing the semantics of measurable numerical quantities. Clearly any theory that does not address the problem of measurement cannot hope to have a complete description of such operators.

Hmmmm... I think I disagree, we can construct localized observables for QM, we do it all the time. Every Heisenberg Operator is an observable with a localisation in time. That is possible because, while we do not have a consistent description of meassurement there are many things we do know about the process and how it appears in the formalism. This allows us to do physics *effectively*. The operationalists never had a problem with QM after all.

 

[Careful]

**
Background Independent: a property of a physical theory or model that must incorporate (1) independence of spacetime coordinates, and (2) a lack of any form of aether. This second condition is far more stringent. Even GR fails this test.**

That is not correct Kea (but it is funny to notice that the meaning of ``background independence´´ causes confusion ) : background independent means any construction which does not depend upon the choice of a background *metric*. Now, if you would choose (1) as axiom, then I can dynamically prefer Minkowski as well as geodesic coordinates (without giving up on covariance !). (2) is probably unphysical, this is something which goes back to Maxwell, through what medium do the waves travel ? Actually, the background metric version can also be criticised similarly : as is well known, the lapse and shift function in the ADM formulation of gravity serve as lagrange multipliers, so why would it be forbidden to add a background metric through lagrange multipliers? As I once commented, background independence is not so clear cut (as our conversation proves again ). Really, it is instructive to read Kretchmann's comments upon the issue of general covariance and how even Newtonian physics can be reformulated in a (ugly) covariant way.


**Logic: a not-necessarily-classical use of syntax with accompanying semantics involving truth-valued propositions and operations such as AND, OR, NOT, implication and quantifiers. **

Clearly a mathematician, but then you can go any side you want to with, say, fuzzy logic.

** (Local) Observable: a mathematical construct representing the semantics of measurable numerical quantities. Clearly any theory that does not address the problem of measurement cannot hope to have a complete description of such operators. **

Well, a *local* observable is rather more than that no.

**Magic: entertainment involving well-trained tigers, hoops, mirrors, saws and people in shiny costumes. **

Nah, these things can all be explained by local physics, the measurement problem cannot unless you do it in MWI.

**Not according to the definitions that I have given above. You have been using a more restrictive set of definitions, in response to the comments of others, but some readers reasonably appear to be finding this loose use of terms confusing.**

Ah, then I was still teasing f-h (what I clearly stated later on).

**
I think I more or less or agree, although you have not been clear, but the fact that QM needs alteration does not necessarily mean that we need to throw QM intuition out the window. **

Well, I have added somewhere the ``deduction´´ where the background *metric* would appear (so although I started off from a more restrictive definition, I think they are effectively equivalent). I agree that it was not crystal clear - in the sense that it is not written in elaborate mathematical form (which would consume more than 20 pages) - but if you would care about following the details (by trying out each particular step yourself) then you will see the conclusion I made there is hard to escape.

**
I wonder if it has occurred to you that your conclusions re the necessity of a classical direction here might in fact be wrong. **

Of course I have considered this. The point is that a classical attempt can logically solve the ``big´´ problems at hand in a conceptually clear intuitive way. I have no crystal ball in which I can predict if one can recover all experimental output in a *nice* way, but my private attempts so far give me any reason to believe that it will; neither is there any historical record about the implausible character of such enterprise.

**
The alternatives involve enlarging one's sphere of logic - seemingly dire perhaps - but alternatives in the spirit of QM all the same.
**

I agree (with both statements).

Cheers,

Careful

 

[Careful]

**
What do you mean by aether? Especially in the context of classical GR?
All LQG people I know seem to consider classical GR to be BI. So your definition seems to be stricter then general usage. **

What does it mean that GR is BI ?? All this can mean is that GR is a reparametrization invariant theory (that is defined independent of coordinates), this has *nothing* to do with the meaning of BI. The ``idea´´ behind BI orginated from the observation that perturbative quantum gravity is not perturbatively renormalizable around Minkowski. So either, this means that GR as a QFT is ill defined (a conclusion string theorists draw) or it means that Minkowski is just a bad background to do perturbation theory around and that it might be that GR as a QFT around a *different* background could be non-perturbatively renormalizable (you still have to explain then why it goes wrong when perturbing around minkowski of course).

**
Hmmmm... I think I disagree, we can construct localized observables for QM, we do it all the time. Every Heisenberg Operator is an observable with a localisation in time. That is possible because, while we do not have a consistent description of meassurement there are many things we do know about the process and how it appears in the formalism. This allows us to do physics *effectively*. The operationalists never had a problem with QM after all. **

Sure, the ``working´´ interpretation of QM is perfectly fine, it just does not solve anything (you still have to go to MWI if you do not wish to improve upon it).

If I were you f-h, I would start by properly learning *classical* GR before you wish to attend a barbecue in my honor. It is clear that I wish to maintain my identity as Careful, please respect that and argue scientifically.


Cheers,

Careful

 

[f-h]

Most people, I think, go by the way it's defined, for example, in Wald: General covariance and no nondynamically defined objects (aether). That's how I understood Kea. But then of course GR is Background Independent.