Is a New Principle Necessary to Resolve Quantum Gravity and Unify Interactions?

[unusualname]

It seems certain that the Standard Model is pretty much correct, the linear group structures do exist in nature. But what is renormalisation doing there, seemingly muddying this beautiful mathematical structure? I think one new physical principle needed is to take the idea of non-local evolution seriously, and just admit that the local structure of QFT is only an approximation. Renormalisation is probably discarding the (small (net)) contributions of the rest of the universe to each and every subsystem within it.

And also I think we need to be less greedy, it may be just not possible to say anything about reality below Planck scale. And maybe gravity is just statistical (entropic)?

And then we have the elephant in the room, human consciousness and free-will. But I think the "measurement problem" is a red-herring, since the universe evolved quite happily before we did, the real open problem is "free-will" and conscious awareness.

 

[Fra]

Fra, the point is that while causal set ideas seem relevant to the question of foundations of quantum mechanics, it is hard to see how they can produce the SM, not to say something BSM (and including the SM). If they can, it will be probably connected to operator theory, C* algebra approach to geometry and, at the end, Connes' theory, but I'd expect 50-75 years time of development. And it surprises me its use for gravity "a la Sorkin", but ok, they could be suitable there.

Now, when I was younger I thought that the number of generations could have a direct connection to quantization procedures. While I do not pursue more this idea, it could be a way to connect foundational arguments with actual particles.

In the last century, I read an enjoyed this one: http://jmp.aip.org/resource/1/jmapaq/v5/i4/p490_s1?isAuthorized=no

Thanks for the link Arivero. Just from the title I suspect it's related to Knuths "derivation" of lorentz symmetry from consistency constraints on any valuation of partial ordered sets.

I definitely think that the basic questions here (not just causal sets) or counting and origin an emergence of ordering can in principle connect to SM, and the action of matter. Ordering and counting are closely related in some views, you can consider ordering defined by counting evidence. So the counters define NEW orders. There is more of course... this is what I mean that that I do not see problems in imagine how it may be done, but I agree that 50-70 years might be realistic. But I don't think that should discourage us. It doesn't discourage me at least. Also, the more people looking at tht is really the problems, the more can ew reduce that time, right?

But after refreshing my memory in the other thread, I think I agree that at least as far as we constrain ourselfs to the so called causal set programme, it seems to have hard to connect to SM like you say. This is in part why I do not like it. Some of the founding ideas are good, but they don't go far enough.

/Fredrik

 

[Careful]

but I think we see the forum as a place to learn. probably more regulars here are not really hard core physicists, but we are here to know ( and sometime fantasize about discovering) what reality is all about.

Forum =
1. a. The public square or marketplace of an ancient Roman city that was the assembly place for judicial activity and public business.
b. A public meeting place for open discussion.
c. A medium for open discussion or voicing of ideas, such as a newspaper, a radio or television program, or a website.
2. A public meeting or presentation involving a discussion usually among experts and often including audience participation.
3. A court of law; a tribunal.

Anyway, I think my bad wording has caused mostly the misunderstanding(twice), not to mention you jumping the gun in the heated battle. I know the unification( classical) EM with gravity has been a loosing battle (Einstein -non-symmetric) , although to this day some people are still trying. but I meant more like QED side of EM, I just used EM as generic

Even then, you will have to do something far more generic than just that.

Careful

 

[Careful]

Somehow I lost track.
Did we manage to identify some new principles or indications what they could be?

I said many times that those things do not happen over public forum.

I guess the last papers Careful mentioned should provide some guideline; especially Sorkin is far from mainstream and could perhaps have some reasonable ideas - besides his causal sets.

Sorkin was mainstream for the first part of his life; he investigated important questions in canonical quantum gravity amongst many other things. Let me phrase it this way, IF nature is discrete, THEN Sorkin's scheme is the only possible one (which has a nonzero chance) I am aware of. But he also works on the foundations of quantum mechanics, extensions of logic and so on.

My problem is that most answers seem to be in the nagative; there are indications how things will NOT work (or only to a certain approximation). But I am afraid that we here cannot be smarter than excellent thinkers out there ...

Well negative answers are the beginning to positive ones. What did you expect? That life is easy? And that you will suddenly deeply realize what the real problems are?
There are people out there working whole their lives at those things and still they come up with partial answers. You would be surprised what people have thought about and never reached the ''media''.

Careful

 

[tom.stoer]

I said many times that those things do not happen over public forum.

Your opinion

What did you expect? That life is easy?

No

There are people out there working whole their lives at those things and still they come up with partial answers.

I know

You would be surprised what people have thought about and never reached the ''media''.

I know

 

[arivero]

You would be surprised what people have thought about and never reached the ''media''.

Feynman "lockbox combination" example was about illustrating it. People works during half a life trying to open a lockbox, and casual by-passers tell them "have you tried, say, 34-54-27?". Surely yes, they have tried.

(hmm, can anybody provide the exact quotation for Feynman paragraph? I remember it only vaguely)

 

[Careful]

Ah, I see now the confusion! Big one, my fault. My point was the reversal: to consider gluons as equal to the the QCD string, and attach quarks to them in order to build the susy scalars (and thus match to the d.o.f of quarks).

Ok, you do suzy in the ''reverse'', I added 1/2 spin, you substract 1/2 spin. Just a tiny question: won't these scalar particles cause lot's of trouble?

Indeed your construction is the right one to build 8 gluons from 3 quarks, and I keep thinking about if it has a meaning too, beyond the usual of representation theory. In my construction, symmetrization wipes the d.o.f. of gluons from 8 to 3, in your construction the pairs allow to go from 3 to 8. This is the expected working of SU(3), juggling between adjoint and fundamental representations, of course.

Long time ago I played with these representations, so I had to refresh my memory by going straight to the Young diagrams.

From the mechanism I sketched, a "light" quark is a quark that you can attach at the end of the string. Somehow, Nature gets to incorporate this "ban to attachment" in the top quark, it decays faster than the theoretical half-life of a possible 'toponium' meson. From naturalness principle, these five quarks should have a hidden symmetry protecting them when, at electroweak symmetry breaking, the top gets its mass. We don't know what this symmetry is, as far as I have read.

Therefore, also my confusion when you suddenly pulled out a 5 of your hat

But it is! When your construction is applied to SU(3) colour, it produces the colour octet. When it is applied to (u,d,s), it produces the famous flavour octet of GellMann. And when applied to families, as you did, it seems to produce again the same content that gluons, and then one is left wondering if there is a relationship between SU(3) family and SU(3) colour. I think this path was pursued in the literature in the late seventies.

I did not delve into this literature (one cannot do everything in life) so I am trying to learn here.

What I build was different: I built 18 (=3x(3x2)) particles of charge +2/3, 18 of charge -2/3, 18 of charge -1/3 and 18 of charge +1/3 by putting quarks at the extremes of the QCD string. Again, sorry the confusion.



Yes, I did it to illustrate the symmetrization, I called it flavour space instead of naming explicitly as SU(5). I though that it followed from my remark on five light quarks, in the typical way that flavour symmetry is always described. The only difference is that usually the SU(3) flavour inside of SU(5) flavour is built only from mass, they take the u,d,s out of the u,d,s,c,b set. I consider all the five quarks equally massless, and I try to commute with electrical charge, so I take d,s,b in my illustration.

In fact, I feel that to use SU(5) in this way is correct because besides finding six +2/3 and six -1/3 in the 15 of 5x5, you can notice that the 24 in 5x5=24+1 happens to contain 6 states of charge +1, 6 of charge -1, and 12 neutrals. That is three generations of sleptons.

Ok, now I see what you try, let me see your original post again and redo your arguments for myself.

Careful

 

[tom.stoer]

... IF nature is discrete, THEN Sorkin's scheme is the only possible one (which has a nonzero chance) I am aware of.

Why? Are there positive reasons for Sorkin's approach, or only negative ones against everything else?

And what do you mean by "discrete"? You can put in discreteness by hand, or discreteness can be a result; spin is discrete even if it follows from a continuous symmetry. If AS or some other ansatz identifies some kind of "minimum physical length" then nature "is" essentially discrete. Contínuous symmetry would then be some kind of "unphysical symmetry", like gauge symmetry.

 

[Careful]

Your opinion

Just common sense.

I know

No, I don't think you know... I thought that I knew a lot about non mainstream approaches, but I get surprised still every day! Always, some obscure Rumanian, Italian or Chinese guy pops up having published nice (similar/partial) results in some unknown editorial simply because the main publishers would regard this as ''dark'' science. I presume that in your case, you are just at the tip of the iceberg.

Careful

 

[Careful]

Why? Are there positive reasons for Sorkin's approach, or only negative ones against everything else?

The main argument is negative, Sorkin's approach is the only one which respects Poincare symmetry (which is a very nontrivial statement). There are some positive arguments too, but they are not too compelling in my view.

And what do you mean by "discrete"? You can put in discreteness by hand, or discreteness can be a result; spin is discrete even if it follows from a continuous symmetry.

Obviously, I mean fundamental discreteness, everybody does so.

If AS or some other ansatz identifies some kind of "minimum physical length" then nature "is" essentially discrete. Contínuous symmetry would then be some kind of "unphysical symmetry", like gauge symmetry.

Haha, sure, would you mind construct the relevant non-local operators for me please ?

 

[tom.stoer]

how can you know what I know?

I mean, I am open enough to ASK, so it should be rather clear what I don't know.

 

[Careful]

how can you know what I know?

I mean, I am open enough to ASK, so it should be rather clear what I don't know.

Therefore my conclusion
But asking is good.

 

[arivero]

Ok, you do suzy in the ''reverse'', I added 1/2 spin, you substract 1/2 spin. Just a tiny question: won't these scalar particles cause lot's of trouble?

Well, my point -which does not follow from the maths, but it is only my personal oppinion- is that these scalar particles actually exist, because they are just the classification of Regge trajectories of the hadronic strings. If you wish, call them diquarks and mesons. The only problem of the group theoretical "constuct" comes with the scalars uu, uc and cc (the extant three pairs from the 15 of 5x5=15+10, which I did not mention in the previous discussion), which fail to have a elementary partner. Only recently I have retaken this issue and I think I am close to an answer.

Of course, it could also be said that all these pairings are pieces of the fundamental string, and then yet to be discovered particles. In such view, our SU(5) would be a kind of tree level version of SO(2^5); this relationship was exposed time ago by the people looking at Chan-Paton charges in open string theory. I find this interpretation more weak, as it is agains Occam razor. But at least, it still would predict three generations.

 

[tom.stoer]

The main argument is negative, Sorkin's approach is the only one which respects Poincare symmetry (which is a very nontrivial statement). There are some positive arguments too, but they are not too compelling in my view.

In which sense do other approaches violate Poincare symmetry? And why should (linear) Poincare symmetry be a good symmetry of nature at all scales?

 

[Careful]

In which sense do other approaches violate Poincare symmetry? And why should (linear) Poincare symmetry be a good symmetry of nature at all scales?

Global Poincare symmetry should be to a very high precision a property of the universal vacuum state. None of the other approaches can achieve that although they have something like local Lorentz invariance. Why should linear Poincare symmetry be a good symmetry? See http://www.physics.princeton.edu/~mcdonald/examples/mechanics/levy-leblond_ajp_44_271_76.pdf Obviously, I, II, III and IV have to hold for vacuum. Recently, local Lorentz invariance has been tested for gamma ray bursts to an extraordinary precision, hence naturalness dictates that Lorentz symmetry must be a symmetry of nature.

Careful

 

[unusualname]

The main argument is negative, Sorkin's approach is the only one which respects Poincare symmetry (which is a very nontrivial statement). There are some positive arguments too, but they are not too compelling in my view.Obviously, I mean fundamental discreteness, everybody does so.

You're obsessed with Poincare Symmetry. If nature is discrete and maybe even has discrete time evolution then it has discrete symmetries, and anything continuous is wrong human thinking.

It's ironic that, at about the same time Planck discovered nature was discrete, Poincare discovered that (non-linear) continuous differentiable models of nature give us irresolvable problems with chaotic solutions that can't be solved analytically. Kinda two big hints to us at the same time.

there are people working on discrete models you know
http://www.phy.syr.edu/research/fundamental_theory/computation.html

 

[Careful]

You're obsessed with Poincare Symmetry.

For GOOD reasons !

 

[arivero]

It's ironic that, at about the same time Planck discovered nature was discrete, (...)

there are people working on discrete models you know
http://www.phy.syr.edu/research/fundamental_theory/computation.html

The point if discretization and continuous limit is well known by mathematicians, and this is still the kind of research of the people working on discrete models.

What Plank discovered was that _angular momentum_ is discrete. Or even more precisely, variations of angular momentum. This is relevant because the infinitesimal area swept by a particle around a central point is proportional (via the mass and an infinitesimal of time) to angular momentum. A problem already noticed by the founding fathers, and obvious during two hundred years to anybody willing to do Fourier transform (having an exponential of the product of xp, it needs to add a constant to make the whole term adimensional).
In some sense Planck constant was similar to Einstein cosmological constant: it was there, but it was ignored or taken negligible until measurement show that it had a definite, finite value.

 

[tom.stoer]

Global Poincare symmetry should be to a very high precision a property of the universal vacuum state. None of the other approaches can achieve that although they have something like local Lorentz invariance.

Why?

If you look at spin or angular momentum you can achieve a "symmetry" w.r.t. to an algebra w/o exponentiating it. That's sufficient for all observables in QM. A continuous symmetry is only required if you start with continuous spacetime for quantization. But if you forget about quantization at all but start with a discrete structure there is no reason for a continuous symmery at all.

If you accept H~0 i.e. "timeless QG" not even time evolution needs to be continuous.

[all you need is a low-energy effective theory that looks like a continuous manifold]

 

[MTd2]

Arivero, I still don`t get what you want to accomplish. You say that quarks do not have a substructure, but it seems that the leptons of the SM have a substructure when you make such construction. Is that it?

 

[arivero]

Ok, now I see what you try, let me see your original post again and redo your arguments for myself.

While you are on it, let me to try to rephrase it now in terms of SU(5). First, this SU(5) is justified either theoretically, as the unique solution to the bose/fermi pairing (post #41 above) , or empirically via the naturalness principle, which tell us that some symmetry must protect the u,d,s,c,b quarks. Perhaps also as the 5 of SO(2^5) in open superstrings.

Our pairings are the 15 of 5x5=15+10, the 24 of 5x5=24+1 and the 15 of 5x5=15+10.

If we wish, we can interpret these charges by using U={u,c} and D={d,s,b} to build SU(2) and SU(3) subgroups of SU(5). But it is more intuitive at this level to keep using the U,D and quark labels. Anyway:

The 24 is colour neutral, and we see that it contains the states for the partners of three generations of Dirac electrons and neutrinos.

15+ 15 contains the partners of three generations of Dirac quarks up and down, plus the six partners of three chiral particles.

Colour is a vector interaction. So Dirac quarks see it, and their partner states of the previous multiplet can hold colour charge. Then we have three "12+12". Adding them to the ones of the 24, we have built 96 states.

Up to here, we have built the Standard Model scalar-fermions.

The chiral particles are colour blind, and so their partners must be. So our extant problem is to explain the role of these six "3+3" states related to uu, cc, cu and their antiparticles. Such "colour blind diquarks" are a strange beast. They are also "electricity blind" in some aspect, they could see hypercharge and weak isospin, but they can not see B-L for instance. (EDIT: The point is that if we assume some U(1)_vector related to B, we can use it to get rid of some thirds and sixths, and the objects can be more manageable. Still, we need a pair of them -cc,uu?- to have charge +1 and other one -cu?-to have zero charge. The point is complicated -to me- because in the electroweak model the W+ and W- particles can be managed separately, while in the Susy electroweak model there is a fermion having two degrees of freedom in the W+ and other two in the W-. And the Z has another of it, massive but chiral)

What is peculiar, and I had not noticed until some weeks ago, is that the mass mechanism for the supersymmetrical electroweak bosons needs to eat not one scalar but two. This is because in SUSY a massless vector supermultiplet gets mass by eating a massless chiral supermultiplet. One of the bosons becomes the spin zero projection of the massive boson, and the other stays as a scalar. So our spureus degrees of freedom seem to be the number we need to break the electroweak symmetry. Then, is electroweak symmetry break also a prediction of the dual "gluon/pion"-quark model? Could be.

Note also that on this count, where the chiral partners do not see colour, the total count of bosons is 96 of the standard sfermions plus six "exotics" plus 24 gauge group, equal 126. It is very tempting to include the graviton in the "gauge group" side, to round off to 128.

 

[arivero]

Arivero, I still don`t get what you want to accomplish. You say that quarks do not have a substructure, but it seems that the leptons of the SM have a substructure when you make such construction. Is that it?

No, neither the quarks or the leptons have substructure as far as I know. I have built substructure for the scalar partners of quarks and leptons, while I kept agnostic about the substructure of quarks and leptons themselves. Furthermore, I show that this substructure has the same form that a flavour group built from the five mass-protected quarks u,d,s,c,b. And I show that the general case with any number of quarks and any number of Dirac generations only solves for three Dirac generations and five substructure quarks.

You can be confused by the word "sfermion" or "scalar-fermion" It is standard jargon to refer to the scalar partner of a fermion.

While it is not used in the maths, the main piece of the construction was to apply the naturalness principle to the masses of quarks and leptons, effectively separating the five quarks which are not in the range of the electroweak scale, and looking for a symmetry for them.

Also, is is only conjectural, not proven, that 1) the substructure is actually a superstring theory, proving that at the end (or for the very start), string theory was right. 1.5) That, incidentally, Chew was right too. 2) That the construction implies the breaking of electroweak symmetry by using the six extra bosons and 3) that the whole thing fits in a 128 dim supergravity multiplet.

 

[Careful]

Why?

If you look at spin or angular momentum you can achieve a "symmetry" w.r.t. to an algebra w/o exponentiating it. That's sufficient for all observables in QM. A continuous symmetry is only required if you start with continuous spacetime for quantization. But if you forget about quantization at all but start with a discrete structure there is no reason for a continuous symmery at all.

You can say what you want and try to cook up whatever it is you want but simple fact is that nature satisfies these laws amazingly well. For any conceivable experiment I do in near empty space, almost any boosted experiment will give me the same outcome. Now, you may try to philosophize and say that there is nothing if space is truly empty and so on and so forth (thus not obeying the standard Fock picture) and that you will be clever enough to find a theory of creation out of platonic nothing. The thing is that once you start creating it and you let your universe grow, Lorentz invariance must be pretty well satisfied on large energy scales. Let me also remind you that nobody has even managed to make sense of these discrete singular geometries in the quantum world. Even in the classical world, this is a hell of a job, see eg. the Sorkin-Rideout dynamics.

[all you need is a low-energy effective theory that looks like a continuous manifold]

Low energy? The continuum description must certainly hold up till scales of 10^{-23} meters and probably still way beyond that. Nobody has a control over the geometry at these distance scales, I would welcome the first paper after 25 years which did

Careful

 

[Careful]

While you are on it,

I will do these calculations tonight, busy now

 

[tom.stoer]

Careful, classical geometry and Poincare invariance is not and will never be tested at the Planck scale. There is no experimental guideline.

 

[Careful]

Careful, classical geometry and Poincare invariance is not and will never be tested at the Planck scale. There is no experimental guideline.

Sure, likewise we do not know whether little angles are not pushing the planets so that they follow their orbits Why don't you go and devise a theory of that ? :zzz:
Seriously, let me give an elementary course in what are good ideas in physics and what are bad ideas:
(a) a good idea always gives instantaneous pay-back. You give something up which makes life a bit more complicated, but you get rewarded by piles of gold. Giving up the continuum does not satisfy this criterion and for sure does not giving up Lorentz invariance.
(b) a bad idea is physically unmotivated, but merely stems from mathematical masturbation excercises such as : (i) help QFT has infinities, we have to cut these out! (ii) let us apply the Heisenberg uncertainty principle where we shouldn't ''we will apply it to space-time coordinates! (which have no operational meaning)'' or (iii) euh the vacuum energy diverges, we can correct this if we modify the dispersion relations (unguidedly), let's do that and proclaim that we magically turned infinity into a finite number (not that it would solve any phyiscal problem).
(i) applies to causal sets, all of them apply to the rest (and I can easily figure out some more of them).

Careful

 

[MTd2]

Arivero,

so, you have a supertring theory, but the symmetry is SU(5). The anomaly cancellation happens in d=10, and the group of symmetries is E8XE8 or SO(32). So, this is a kind of non critical string, is that it?

 

[arivero]

Arivero,

so, you have a supertring theory, but the symmetry is SU(5). The anomaly cancellation happens in d=10, and the group of symmetries is E8XE8 or SO(32). So, this is a kind of non critical string, is that it?

Yes and perhaps no exactly. http://www.slac.stanford.edu/spires/find/hep/www?j=PHLTA,B188,58 did an argument where the SO(32) group appears after world sheet quantization of five quarks. And they conjectured, in other work, that this number was coming from the dimensionality of space time.

And the construction does not use the dimensionality of space time, so it is general. If it is connected to Marcus-Sagnotti, then it is more a kind of low-energy or un-quantified aspect of the critical string.

EDIT: More important, if we accept the interpretation of bosons as QCD strings straightly -it is not needed for the math, but it is the most obvious interpretation- then we answer to the main criticism of susy, because we know what all the bosons in the sfermion sector have been already found The only BSM particles should be the partners of the gauge bosons.

 

[qsa]

Somehow I lost track.

Did we manage to identify some new principles or indications what they could be?

I guess the last papers Careful mentioned should provide some guideline; especially Sorkin is far from mainstream and could perhaps have some reasonable ideas - besides his causal sets.

My problem is that most answers seem to be in the nagative; there are indications how things will NOT work (or only to a certain approximation). But I am afraid that we here cannot be smarter than excellent thinkers out there ...

It is happening again, the thread started beautifully, but side issues took over. I have a question:do you think holography is inconsistent with the virtual particle-antiparticle picture of forces or graviton. and if that is true, shouldn't that be the most important conflict to be worked on to understand QG.

 

[arivero]

It is happening again, the thread started beautifully, but side issues took over. I have a question:do you think holography is inconsistent with the virtual particle-antiparticle picture of forces or graviton. and if that is true, shouldn't that be the most important conflict to be worked on to understand QG.

I disagree. The thread started badly, going straight againts its own tittle, menacing to focus in gravity, and avoiding any mention of the problems of BSM. After that, we got to do some post on principles; I myself invoked naturalness, and some other were mentioned. And we did also some calculations. Fine enough for a PF thread.

I will ask again: Why the heck do all of you identify BSM="lets speak of gravity"? Is it an idea of your own, or does it come from some TV series? It should be pretty obvious: if it does not contain the SM in some limit, it is not BSM.