LHC - the last chance for all theories of everything?

[tom.stoer]

*ANY* mathematical system IS a Universe (he calls it Level 4 Multiverse) For example, Conway game of Life IS a Universe. Including ours.

I would agree if we talk about platonism where all mathematical structures have an own existence. The material world = our universe is a manifestation of this existence. Plato thought that the material world is a kind of image or shadow of the ideal world. But Plato never thought - and I would not agree - that (the other way round) all ideal worlds must have a physical manifestation. (This is only a remark and not really required in our discussion).

There is nothing special about SU(3).

Of course there is something special about SU(3). It's the the only symmetry structure for which a physical manifestation in strong interaction is KNOWN. SU(4) might be possible and might be realized in "other universes", but that is SPECULATION.

Why not SU(4)? Well, may be there is a Universe with SU(4), other types of particles, different types of beings there. But more likely almost all other universes are sterile, because they can not generate intelligent life - we know how many conditions must be satisfied to create us, humans.

QCD with a different number of colors (e.g. N_C=2) is qualitatively identical to our world with N_C=3. Many lattice gauge simulations use two or three flavors (N_F=2,3) only and are able to reproduce the hadron spectrum within a few percent. As far as I know QCD with N_F=8 which corresponds to a heavy fourth fermion generation cannot be ruled out experimentally.

Is TOE of our universe the simplest non-sterile universe?

What do you mean by simple?


It seems to me that instead of a physical multiverse (in the context of string theories) a new speculation of mathematical multiverses and their physical manifestations is proposed. I would say that a candidate for a ToE should do something like that: propose a kind of framework for theories and deduce an idea how "nature" selectes one possibility. From what I understand the selection principle is missing - and this defect is promoted to a feature of the whole approach.

Imagine that pure QCD + UV completion of GR is the ToE. Then I would expect that within some framework, e.g. SU(N_C) with N_F plus UV completion of SO(D-1,1), one can answer the questions "why is N_C=3?", "why is N_F=6?" and "why is spacetime four-dimensional, i.e. D=4)".(Of course this candidate theory is wrong as it predicts the non-existence of electro-weak interactions.) Theories as we know them today are not able to answer these "why-questions". String theory tried for two decades but surrenders now by proposing the idea of the landscape or multiverse.

And this is my point: If you (or Tegmark) replace the ontological meaningless idea of physical multiverses by the (even more) meaningless idea of mathematical multiverses plus their possible physical manifestation w/o any idea for a selection principle, then the whole discussion is "void". If nobody can tell me why nature selected SU(3)_C, then it is no answer to say "nature did not select anything but realized all SU(N)_C-universes in a random and democratic way - and eventually casted me into one of them where N_C=3." This is metaphysical speculation and has nothing to do with science.

Don't get me wrong: I like the multiverse(s) as a set of candidate theories, but I expect some kind of framework plus selection principle to answer the "why-questions". If the latter does not exist or emerge, then the whole approach is meaningless and useless.

Remark: My impression is that the "why-questions" were not so important for a couple of decades because physicists hat a lot of work to do after the QM revolution (inventing QFT, renormalization, current algebra, soft pions, standard model, chiral perturbation theory, lattice gauge theory, ...) - and perhaps these "why-questions" have simply been ignored; therefore we are not used to ask and to answer them. But as we now try to figure out what a ToE is, how it can look like (logically, mathematically, physically, ontologically?), what the requirements and preconditions are etc., we must focus again on these questions and cope with them, otherwise we are lead astray.

 

[Finbar]

Do you know the concept of radical idealism?

Kant claimed that there is a "thing-in-itself" which is independend from the human mind, but inaccessible in terms of phenomenology. Nevertheless this "thing-in-itself" is the core of his ontology. Kant was already on the way to idealism.
...
".

I just think that there is only one reality. That which constitutes matter also constitutes experience.

Physics then should be a description of this single reality. Now its almost certainly the case that any mathematical description of this reality will be incomplete. If it was complete then this would mean that Tegart is right and that dualism is correct. I think however we already have evidence that our physical theories are incomplete descriptions of reality. For instance the uncertainty principle could be interpreted as saying that any attempt to write a theory that accurately describes reality will have uncertainties. Thus the uncertainty is in the description and not in reality itself. I'm not really sure where I stand in terms of realism/idealism/positivism. I'm a realist in the sense that I think the moon exsistence regardless of whether I look at it. But the same time I take a hardline to any idea of a independent internal/external reality. My experience of the moon and the moon are only spatially separated hence they are different phenomena in the same reality.


I really think this dualist view is a stain in the philosophy of too many physicists. I think the positive view of "shut up and calculate" is the best approach to physics(in most cases). But when Tegmart write's a paper with clearly retarded philosophical assumptions its a little annoying.

 

[Dmitry67]

1
Of course there is something special about SU(3). It's the the only symmetry structure for which a physical manifestation in strong interaction is KNOWN. SU(4) might be possible and might be realized in "other universes", but that is SPECULATION.

2
As far as I know QCD with N_F=8 which corresponds to a heavy fourth fermion generation cannot be ruled out experimentally.

3
What do you mean by simple?

4
From what I understand the selection principle is missing - and this defect is promoted to a feature of the whole approach.

1,4
I believe you have the same misconception people usually have about MWI. People tend to say “ok, there are different branches, but why *I* am in this particular branch?” while all branches are symmetric and “you” in all branches are asking the variations of the same question “why I am in this branch?”

Exactly the same we have here. What do we call “real”? I take an apple. I touch the surface, I sense its smell and taste. It is all about the correlations between output signals from my brain (I give command to muscles to take an apple) and input signals (smell, taste).

Now imagine structures in different non-sterile Universes. Intelligent being there would definitely call their environments “real” for the very reasons I described above. They will also call other worlds “imaginary”. Finally these beings will ask your question: why my world is SU(3)? Or why my world is 93-dimensional? Why my geometry is non-commutative? Or why space in my world is made of pixels (is asking some creature living in the Conway’s game of life world)

So I not only refuse to answer your question about the selection rule, but I (after Max Tegmark) insist that there should not be any selection rule!

2
I’ve heard that neutrino oscillation experiments had ruled out the 4th generation

3
Lets say the total length of all formulas. I know, it is not perfect as it depends on the mathematical language used.

 

[tom.stoer]

Regarding 1,4:
If you insist in this mathematical mutiverse w/o any selection rule then we have to agree that we don't agree :-)

Regarding 2:
This argument is forbidden I am my ToE since it does not contain neutrinos and weak interactions :-)
Seriously: thanks for the information; do you have a reference?

Regarding 3:
After having discussed 1 and 4 this is no longer important :-)

 

[tom.stoer]

Finbar,

I agree that there is only one physical reality. I don't like the dualist view. Dualism with mind-independent reality is awkward since it does not allow us to describe the interaction of mind and matter (or whatever the two entities are). As soon as we are able to decsribe this interaction we are forced towards monism.

But nevertheless there seem to be different layers of what we call reality; one layer is our mind.

Look at the rainbow; you have three different "views":
(a) the rainbow as it is perceived
(b) the physical constituents of the rainbow = the raindrops, lighrays etc.
(c) the mathematical description in terms of geometry etc.

(a) is unthinkable without YOU!
(b) is rather clear for the rainbow but not known for the real quantum world; our all-days language is no longer suitable for describing the quantum reality
(c) does "exist" even if you and the raindrops does not.

Now let's assume for a moment that the mathematical Hilbert space is not only a description of the reality but IS the reality (bad idea: we immediately face the problem of the collapse of the wave funtion which is not described in terms of quantum mechanics; so this reality is incomplete). In that case we agree that there is one reality which IS the Hilbert space - done!

I think the major step forward is that we agree that there is a reality and that we do not insist on idealism or positivism. The problem then is that we do not know what this reality IS.

If we would instead think of the q.m. formalism as a pure description only and if we say that there IS nothing else but this description (no external reality), then we omit the measurement problem, but we are left with the situation that after all we cannot answer the question "why do all physicists use the same description?".

In the very end I believe that every physicist tends to realism. After all calculations are done and after the experimental data have been analyzed he/she wants to know what there really IS (including himself/herself)

 

[Fra]

Tegemark's reasoning is not appealing to me either and I didn't follow this discussion but I just jump in with a comment on one thing, a simple response to one specific question from my point of view.

All I believe is that there is "something out there" independent from our mind - a "physical reality" - simply because of the fact that we all agree on some fundamental experiences / phenomena / measurements which is hardly thinkable with radical idealism = w/o any mind-independent entities or structures. Why should totally independent human minds agree on some structures if not because a mind-independent reality?

IMHO because what you think of as observer/mind independent structures, is emergent as a result of observers/minds/systems are interacting. As a form of negotiation process.

The why and HOW this process occurs, and what the result is would I think answer a lot of the previous questions as to "why this symmetry and not that one". There is no currently available argument but the lineout is along the lines that, what equilibrium structures would be expected on a market where the players are rational to the extent possible?

In such a game, there is a group selection pressure in the sense that you can not largely violate the negotiated "rules" and stay in equilibrium.

I think physical law might eventualyl be understood as such "negotiation process" where matter are the players. There specrum of laws/rules and players population the equilibrium would thus expecte to be connected.

/Fredrik

 

[atyy]

"why do all physicists use the same description?"

Zurek, http://arxiv.org/abs/0707.2832

 

[tom.stoer]

Fredrik,

I am not sure if I understand.

If it is a collection of minds that negotiates then I have to ask "how does this negotiation work?". OK, I don't think that you mean this.

If it's matter (whatever matter IS) that negotiates, then the questions are a) how this "negotiation" differs from "interction" and what (which "framework") sets the rules for the negotiation?

Or do you think that the physical laws emerge as a negotiation process? Then again: what are the rules for the negotiation and where do they come from?

Or do you say that only a description of the fundamental reality emerges from this negotiation? If so, the description is created by us humans. Therefore other communities of intelligent life could come to a totally different structure than SU(3) but still describe the same reality. If this is the case I would simply call this a "dual description". In that case again I would ask what is the reality behind this description.

ATTENTION: There is one general argument not to take the descriptions too seriously as reality per se. If you identify the description with the reality, then every time you are forced to change the description, you automatically destroy your ontological basis. During the paradigm change from classical to quantum physics the description changed - but certainly not the reality!

 

[Fra]

If it is a collection of minds that negotiates then I have to ask "how does this negotiation work?". OK, I don't think that you mean this.

Yes I'm not talking about human minds - it's just by analogy.

If it's matter (whatever matter IS) that negotiates, then the questions are a) how this "negotiation" differs from "interction" and what (which "framework") sets the rules for the negotiation?

There is no difference. The framework of negotiation is subjective, or relative to the observer.

Or do you think that the physical laws emerge as a negotiation process? Then again: what are the rules for the negotiation and where do they come from?

Yes, both interaction as per some law, and the law itself are different hierarchies of evolution in my abstraction. The only difference between a state in the normal sense and law, is it's confidence or inertia.

Or do you say that only a description of the fundamental reality emerges from this negotiation? If so, the description is created by us humans.

? why? I wouldn't say so, because the negotiators are not humans, it's physical systems, ie matter. Objectivive stable law, corresponds (in my view that is) to equilibrium at the corresponding level. Usually, it's only this most stable level where the evolution is not distinguishable that we would usually label "law".

So the question, what are the rules of negotiation? Well, that is the same as to ask what are the rules that selected the laws of nature. I do not have an answer yet. I just describe here a general point of view, a suggestion of a research program.

Ariel Caticha has a similar, but less radical view, where he thinks the laws of nature are derivable from the rules of rational inference in an information theoretic approach. But he works in a more objective context that I. He also doesn't reconstruct the continuum.

What I have in mind, as the program is to reconstruct probability theory, from a discrete poitn of view, and then argue that there exists natural rational measures of information divergence due to uncertainty that is the basis for the physical action of the least action principle. In this view, all "measures" will by construction get a kind of mass(complexity), that works as an inertia in negotiation processes.

The heave opinon will have large impact than the light one.

Combine this with systems of probability spaces that are related by transformations, leads to a measure-complex consisting of several related discrete proability spaces (discrete refers both to event index and probability value) and physical actions are then derived from the inference properties of this system.

So one such system might correspond to a physical system, say an elemetary particle. The mass is thus related to the complexity.

Also the internal transforamtions are those that leaves the complexity (amss) invariant and also leaves the communication interface to the environment invariant. The degrees of freedom left are tamed by assuming he internal equlibration is that which is most self-preserving - just like the human brain is constantnly reorganising inputs in the way that's assume to in its' interest.

This also aims to explain the origin of mass as a kind of game, where accumulation of mass is like accumulation of confidence. There is a kind of argument that this is simply self-presevation, those systems whose actions doesn't try to keep/increase confidence in the current structure will not survive - and thus such measures-complexes (matter) are not observed in nature other than transiently.

/Fredrik

 

[Fra]

Or do you think that the physical laws emerge as a negotiation process? Then again: what are the rules for the negotiation and where do they come from?

This touches upon Smolins ideas on laws beeing a result of evolution. Someone asked him that, then must their not be some meta laws of this evolution whose origin you would similarly question? He didn't give a clear answer.

But in my view that, I'd say no, there is no such laws. Instead my idea is to argue that the laws are emergent from a point where no laws at all are distinguishable, at this point the objection itself dissapears. I associate this to the *inside view* of a "TOE level" (total unification) - this is totally unlike the TOE level that we seek in an high energy accelerator experiment. This is what I would call a external view of the "TOE action".

/Fredrik

 

[Dmitry67]

Regarding 1,4:
If you insist in this mathematical mutiverse w/o any selection rule then we have to agree that we don't agree :-)

Regarding 2:
Seriously: thanks for the information; do you have a reference?

2
I have found only this (sorry for quoting Wiki, I remember I have seen it somewhere else too):
http://en.wikipedia.org/wiki/Neutrino#Types_of_neutrinos

Measurements of the Z lifetime have shown that the number of light neutrino types (with "light" meaning of less than half the Z mass) is 3

1,4
ok, let's agree on disagreement.
But to understand your disagreement, could I ask you a question about what is "real".

Are virtual particles "real"?
A) Yes, like the regular ones. They just don’t have 'free' energy. But on the short time intervals there is almost no difference.
B) No, only real particles are real. Virtual particles are just a mathematical method of calculation of interaction between real particles.
C) Both real and virtual particles are just mathematical methods of calculation of the correlation between macroscopic events. Only macroscopic events are real.
Note: Hawking radiation and Unruh effect (so different accelerated observers do not agree on the number of ‘real’ particles) strongly suggest A) or C), not B)
Note 2: In MWI there are no particles at all, but question is still valid if we talk about wavefunction.

 

[Finbar]

Finbar,

I agree that there is only one physical reality. I don't like the dualist view. Dualism with mind-independent reality is awkward since it does not allow us to describe the interaction of mind and matter (or whatever the two entities are). As soon as we are able to decsribe this interaction we are forced towards monism.

But nevertheless there seem to be different layers of what we call reality; one layer is our mind.

Look at the rainbow; you have three different "views":
(a) the rainbow as it is perceived
(b) the physical constituents of the rainbow = the raindrops, lighrays etc.
(c) the mathematical description in terms of geometry etc.

(a) is a phenomena which accurs in a subset of the universe(you) (b) is another phenomena local to the interaction of the raindrops with light. (c) is a description. If I have a non-relativistic theory it may describe reality well enough in certain limits but we know its not a complete description. Any mathematical theory of a rainbow is still just a description the theories existence has no effect on the nature of the rainbow.

So in conclusion my view is that (a) and (b) are phenomena of some reality. (c) is an attept to describe that reality.

Tegemark's view is that there existence some (c) which IS (b) and that he can ignore (a).

 

[tom.stoer]

@Dmitry67,

Regarding the reality of virtual particles: I think this is confusing, as strictly speaking there are no real particles at all! A particle has to interact with some detector in order to be detected. All those interactions are described by the exchange of virtual particles, so the detector registers virtual particles only. The real particle that escapes to infinity w/o absorption or whatever is invisible to us.
=> C) = mathematical tools
[the distinction between real and virtual particles comes from the distinction between the quantum process subject to experiment and the measurement itself; in the process only virtual particles are involved; in the measurement we register the asymptotic, outgoing real particle; this is a framework for doing certain calculations - quite successfully - but not a solid basis for an ontology]

Regarding the wavefunction: I would not say that a wavefunction is "real". If it were real then the "collapse of the wave function" during a measurement would be real as well - and I don't like this idea :-)
As an alternative you could try to construct two different "evolution operators" in QM; one is the well-known unitary time-evolution operator U(t,t°), the second one is a non-unitary R which - when applied to a wave function - forces it to collaps to the eigenstate corresponding to the eigenvalue that has been measured. R is applied to describe the measurement process. This has been proposed by Penrose - and I don't like this idea, either.
=> C) for the wavefunction as well

What is "real"?
Honestly speaking I don't know. What I was trying to explain is the following:
A) QM as it is understood today mainly serves as a framework that predicts experimental results; with this interpretation you will never run into difficulties when talking about reality; you simply deny that QM describes reality but you insist on the position that QM *only* predicts experimental results.
B) I do not see anything in the QM framework that could be "real", strictly speaking. Are Hilbert spaces real? Path integrals? I don't think so. They are just tools to predict experimental results. This is true for classical physics as well. Of course I would say that "spacetime exists". But I would not say that" spacetime is a four-dim. pseudo-Riemann manifold"; strictly speaking I would say that "spacetime is described mathematically by a a four-dim. pseudo-Riemann manifold"
C) Nevertheless I am convinced that there is something beyond this abstract descriptive layer that is indeed real! The moon is real - and a pair of entangled photons is real as well. They exist even if we don't look at them, even if we do not measure them. They have an existence that is independent of ours - and of our descriptions. The reality of the world does not change because we are changing the methods to describe it. Going from Newton to Einstein did not mean that the reality or the existence of spacetime has changed; only the description has been improved to some degree.
D) So I am a realist in the philosophical sense. I believe that there is something like "real physical entities". They need not be known entities like "pointlike masses" or "fields". With our physical and mathematical tools we are coming closer and closer to a description of this reality; but it will remain a description, an image, a model, not the reality itself. I do not identify reality with its description.

 

[tom.stoer]

Tegemark's view is that there existence some (c) which IS (b) and that he can ignore (a).

So let me say this in my own words just to make sure that I understood everything correctly.

Plato says that it's the "ideal triangle" that exists primarily. All drawings of triangles etc. are only secondary shadows or incomplete models (Allegory of the cave). I would agree with him in the context of mathematics, i.e. for mathematical entities like (e.g.) triangles.

Aristotle says (just the opposite) that the ideal triangles are only secondary abstractions of drawings, physically existing triangles etc. I do not agree with him in the context of mathematics, but e.g. in sociological contexts, i.,e, for terms like "goodness" as a secondary abstraction of several good deeds.

Now comes Tegmark and says that we can avoid both dualistic interpretations and find a monistic one that goes as follows:
1) there is a rather powerful mathematical framework which allows us to describe quarks q, q', q'', ..., interaction processes of quarks p(q, q', q'' ...) etc.
2) there is some reality populated by Quarks Q, Q', Q'', ... interacting in Processes P(Q, Q', Q'', ...)
3) instead of saying that (2) is "the reality" and (1) is "its description", this framework allows us to write q = Q, q' = Q', q'' = Q'', p(q, q', q'' ...) = P(Q, Q', Q'', ...).
The "=" does not mean "represents" or "describes" but "IS" in the sense of "is identical with".

So it's not only that we have e.g. the situation that two Quarks Q and Q' are identical Q=Q', which is mapped to the description as q=q', but that the description q of the Quark Q and the Quarks Q itself are identical. (of course I don't want to say that the reality is indeed populated by quarks; it's just an example; it could have used malt whisky as well)

Is it that what he says?

If yes (and if one can get rid of the multiverse) this is fascinating and shocking!

 

[moniker2]

Would you ever consider a Toe with imaginary units of energy, time and matter?

 

[Dmitry67]

Would you ever consider a Toe with imaginary units of energy, time and matter?

Time units are already imaginary in SR :)
Also I expect LHC to confirm Standard Model on high eneries - instead of some new particles I expect negative probabilities become inevitable.

 

[Dmitry67]

If yes (and if one can get rid of the multiverse) this is fascinating and shocking!

Yes, this is what he says: mathematics does not DESCRIBE the reality, it IS reality.

But if you do this step, then the next step you unavoidable. If some mathemetical system describes OUR Universe, then why it is special? "What burns fire into these formulas?" (c) Hawking.

If Mathematical system IS physical reality then no special agent is needed for the formulas to "live". Hence, any (correctly defined) mathematical system MUST BE a universe.

 

[Chronos]

The LHC is not even remotely capable of the power levels routinely generated by grb's, supernova, inspiralling neutron stars, etc. I doubt anything very novel will emerge from it. Information theory might be a more powerful instrument. If our fundamental assertions are correct, computational results should be consistent with observation. If not, something is either missing, or incorrectly modeled, imo.

 

[Dmitry67]

The LHC is not even remotely capable of the power levels routinely generated by grb's, supernova, inspiralling neutron stars, etc.

The temparatures in such processes is only few billion degrees.
LHC gives MUCH more then that!

 

[marcus]

The temparatures in such processes is only few billion degrees.
LHC gives MUCH more then that!

Dmitry, a square kilometer receives several million particles a year with energies in excess of 1000 TeV.

That is 10^15 eV and if one were to convert that to temperature in the usual way one would say 10^19 kelvin. Ten billion billion kelvin.

But are there processes currently going on in our galaxy that you would characterize as having a temperature of ten billion billion kelvin?

I guess my point is that temperature can be a tricky concept because the particles are produced by non-equilibrium processes. We have this mental reflex to convert particle energies to temperature, but it does not always give the right intuitive understanding.

Cosmic ray particles with energies in excess of 10^20 eV have been observed. If one converts that in a kneejerk way to temperature, one would say 10^24 kelvin. This is more than a "few billion degrees".

It is a quadrillion billion degrees.

But does that conversion to temperature really help you understand cosmic ray particles, or the processes that produce them?

 

[Dmitry67]

Yes, but there is no clear explanation for such rays.
So yes, they have been observed.
For example, in supernova explosion temperature is only 10**11 - 10**12 K

 

[marcus]

I'm not sure you understand my point. I am questioning the usefulness of assigning a temperature to a supernova and then expecting that temperature to characterize the energies of the cosmic rays accelerated by some nonequilibrium supernova processes. For example see this paper published in Nature.

http://arXiv.org/abs/astro-ph/0411533
High-energy particle acceleration in the shell of a supernova remnant
H.E.S.S. Collaboration: F. Aharonian, et al
9 pages, 3 figures, published in Nature
(Submitted on 18 Nov 2004)
"A significant fraction of the energy density of the interstellar medium is in the form of high-energy charged particles (cosmic rays). The origin of these particles remains uncertain. Although it is generally accepted that the only sources capable of supplying the energy required to accelerate the bulk of Galactic cosmic rays are supernova explosions, and even though the mechanism of particle acceleration in expanding supernova remnant (SNR) shocks is thought to be well understood theoretically, unequivocal evidence for the production of high-energy particles in supernova shells has proven remarkably hard to find. Here we report on observations of the SNR RX J1713.7-3946 (G347.3-0.5), which was discovered by ROSAT in the X-ray spectrum and later claimed as a source of high-energy gamma-rays of TeV energies (1 TeV=10^{12} eV). We present a TeV gamma-ray image of the SNR: the spatially resolved remnant has a shell morphology similar to that seen in X-rays, which demonstrates that very-high-energy particles are accelerated there. The energy spectrum indicates efficient acceleration of charged particles to energies beyond 100 TeV, consistent with current ideas of particle acceleration in young SNR shocks."

If you make a simpleminded conversion of "beyond 100 TeV" to temperature, then it does not make sense. The simpleminded conversion of 10^14 eV would be 10^18 kelvin. That is one billion billion kelvin.
No one supposes that the supernova explosion is characterized by a temperature of 10^18 kelvin. In fact it is an intricate process, or combination of processes, some of which do not have a well-defined temperature.

One would not say that the supernova has a temperature of "beyond 10^18 kelvin", and yet it apparently produces cosmic ray particles accelerated beyond 10^14 eV.

Something more recent on this general topic (supernova remnants and cosmic rays) is a 2008 white paper:
http://arxiv.org/abs/0810.0673

 

[Dmitry67]

marcus, ah, I see, I agree.
BTW, any news about how such particles violate GZK-limit?

 

[marcus]

BTW, any news about how such particles violate GZK-limit?

Dmitry, I think that the specialists in UHECR say that the ultra-high-energy particles come from comparatively near and have not been traveling long enough for them all to interact with the CMB photons. I don't have any recent news and am not so well-informed about this, so we should check to be sure.

As I recall, they suspect that cosmic rays are either generated in our own galaxy or come from comparatively nearby active galactic nuclei (AGN).

Yes, I checked---Wikipedia gives some numbers.
The GZK cutoff is 5 x 10^19 eV, and it only applies to distant sources---the mean free path for the reaction with the CMB is 160 million light years.

160 million lightyears is fairly close to us. There are enough AGNs within that range. If I remember there used to be a puzzle about GZK, somebody had seen too many UHECR, they thought. Then the Auger observatory found there were not too many. The UHECR could be explained as coming from nearby AGN. So this puzzle was cleared up. I think Auger even pinpointed some nearby AGN sources of cosmic rays (though not of this ultra high energy.)

 

[Finbar]

If yes (and if one can get rid of the multiverse) this is fascinating and shocking!

Yeah you can't say QM describes a mathematical reality unless you use the many worlds interpretation. Otherwise clearly QM is not a description of reality at all as one does not ever measure the wave function. So one cannot get rid of the multiverse. In that case it is only the sum of these worlds that can constitute a mathematical universe.

 

[Vanadium 50]

I think Auger even pinpointed some nearby AGN sources of cosmic rays (though not of this ultra high energy.)

That correlation has either weakened or disappeared, depending on who you talk to.

 

[marcus]

That correlation has either weakened or disappeared, depending on who you talk to.

I'm glad to learn of this! Do you have any paper or news item that tells about it?

 

[tom.stoer]

Yes, this is what he says: mathematics does not DESCRIBE the reality, it IS reality.
But if you do this step, then the next step you unavoidable. If some mathemetical system describes OUR Universe, then why it is special?

This question stillmakes sense.

You should take into consideration that for many known mathematical frameworks you can construct a meta-framework from which the individual frameworks can be derived. In that case the meta-framework can provide a selection rule.

 

[Dmitry67]

Could you explain your motivation, why do you want to find some "selection rule"?

Selection rule adds complexity. Number 456 contains more information then ALL integers, because you can ask "why 456? what is selection rule?" For ALL integers you don't need a selection rule.

 

[Vanadium 50]

I'm glad to learn of this! Do you have any paper or news item that tells about it?

Glad? Indeed. Why?

The most positive interpretation comes from Auger themselves: see their presentation at ICRC 2009 in Lodz. They say that the correlations have "not strengthened" or "weakened", despite having added more data to the analysis.

Others did the natural thing and subtracted the new numbers from the old numbers to look at the correlation in just the events they added. Nothing much there.

 

[marcus]

Glad to get new information about an interesting question like the origin of UHECR.

The most recent thing I've seen about this is April 2009
http://arxiv.org/abs/0904.4277
Correlations between Ultrahigh Energy Cosmic Rays and AGNs
Glennys R. Farrar, Ingyin Zaw, Andreas A. Berlind
(Submitted on 27 Apr 2009)
"We investigate several aspects of the correlations reported by the Pierre Auger Observatory between the highest energy cosmic rays (UHECRs) and galaxies in the Veron-Cetty Veron (VCV) catalog of AGNs. First, we quantify the extent of the inhomogeneity and impurity of the VCV catalog. Second, we determine how the correlation between the highest energy Auger UHECRs and VCV galaxies is modified when only optically-identified AGNs are used. Finally, we measure the correlation between the published Auger UHECRs and the distribution of matter. Our most important finding is that the correlation between UHECRs and AGNs is too strong to be explained purely by AGNs tracing the large scale distribution of matter, indicating that (barring the correlation being a statistical fluke) some substantial fraction of UHECRs are produced by AGNs. We also find that once we take into account the heavy oversampling of the VCV catalog in the Virgo region, the lack of UHECR events from that region is not incompatible with UHECR having AGN sources."

If you have a link handy to some particular abstract from the conference you were talking about, I'd be glad to give a look.

 

[moniker2]

Maybe it's time to redefine temperature.

 

[tom.stoer]

Could you explain your motivation, why do you want to find some "selection rule"?

Selection rule adds complexity. Number 456 contains more information then ALL integers, because you can ask "why 456? what is selection rule?" For ALL integers you don't need a selection rule.

The explanation is as follows:

I believe that we are living on one of many possible worlds. Possible means logically or mathematically possible = (at least) consistent.

As I said I think that a universe with (e.g.) a fourth heavy fermion generation would be "possible" and would not differ so much from ours. So we must take this into account when we study candidates for a ToE.

Then I believe that (even if you insist on some kind of a multiverse) not ALL but only a certain SUBSET of all possible worlds exist "somewhere". Of course I do not know what this subset is but I strongly believe in this subset.

Reason 1: I don't like the multiverse idea, because it has too much metaphysical ballast and does not satisfy Ockham's razor criterion; I don't believe in an entity that is in principle invisible, not measurable and therefore unphysical. Compared to the multiverse one selection rule seems to be much simpler and much easier to believe in (at least for me).
Reason 2: All discussions regarding the multiverse idea (many-worlds interpretation, landscape) I ever participated in came sooner or later to a point which I would describe like "I cannot explain why it's this way or that way - and therefore it's both ways!" That's not a sientific argument but an excuse only.
Reason 3 - and this is the most important one: even if you insist on the multiverse idea, it is by no means clear why ALL logically consistent ToEs should be physically real - why not only a certain subset? Compare it to evolution: not ALL possible species are alive, but only a certain subset. Why is this? Simply because there are selection rules (not hand made, but external to the species' ToE framework = the DNA, namely the environment) which suppress or constrain the evolution. In our case this could be some meta-theory, but nevertheless it must not be excluded.

So this selection rule could restrict the number of real worlds to just ONE, or it could drive an evolution of universes such that we are living in a TYPICAL one.

(Smolin's idea was that a universe spawns children from black holes, so a selection rule is that a typical universe is one in which the numer or density of black holes is maximized such that as many baby universes as possible are spawned - I don't think he was able to define this mathematically and prove why our universe nearly maximizes the number of black holes).

Finally I would like to explain reason 4 - even if I did not study the paper in question in all details: From a philosophical point of view I still do not see how the concept of a DESCRIPTION of a world is converted into the WORLD itself. I still believe in a kind of dualism, namely that the world and its description are two different "entities". Therefore the mathematical frameworks do not exist on the same level as the worlds.
Of course there is a sketch of a proof: The mathematical framework is eternal and exists "forever". It does neither exist "in time" nor "in space". But a universe can be created out of "something" and eventually it can fade away. Therefore the lifetime of a universe could be finite, whereas the lifetime of the corresponding mathematical framework is certainly not (homework: when will the prime numbers die?)
If you believe that the prime numbers will never die, then
a) either the universe (by similar reasons: all universes!) is (are) eternal, which means that only eternal universes are allowed, which is a selection rule!
b) or the prime numbers exist in some "outer space" = some meta-theory in which the "universes" = ToEs are embedded. In that case the eternal framework turns again into an eternal description of a mortal world, which proves that the two entities in question do not exist on the same level.


(Logical positivists grounded some of their disproofs in a mismatch of categories. E.g. they claimed that the color red is not identical with a certain wavelength, but is its representation. I have the feeling that this concept for a ToE is vulnerable due to similar reasons).

My conclusion is that I am still not convinced that the entity "description of the world" is identical with the "world" it describes.

Last but not least I would like add an idea how ToEs could be categorized:
- first requirement is that the ToE incorporates all known interactions in some way, e.g. as low-energy effective theories
- second requirement is that the ToE is a consistent mathematical framework, i.e. it must be mathematically well-defined
- third requirement is that the theory must post-dict at least some known facts like the standard model gauge symmetries, number of generations, number of space-time dimensions etc.
- forth requirement is that the theory must predict new phenomena which should be (at least in principle) falsifiable by experiment
A (meta) requirement) for a (meta) ToE is that the theory in question can at least support why she is the ToE. That means if the ToE contains a certain mathematical structure, there should be an explanation in terms of deeper structures or insights why this structure MUST be contained. This is subtle, of course. EXample: if the ToE is grounded on local gauge symmetries, I would like to know WHY.

 

[moniker2]

Maybe you can use Knot theory to satisfy Ockham's razor criterion in the multiverse idea.

 

[Dmitry67]

Tom,

Regarding 1,2,3 and Occams razor. In informational sense, “information should not be multiplied unnecessarily”. When we build something, we add building blocks, adding new information an every step. That is why every new stone you put in the building must be well justified. However, using this method you can add only finite number of stones/entities. You can’t define integers by providing a complete list, right?

When we manipulate with infinite numbers of entities we go in the opposite direction: we start from the Universum, and then remove something. Each removal adds new information (and list {12438, 59859599, 858585, 77} contains MORE information than a list of ALL integers), so each removal must be justified.

It seems you understand it and for that reason you call a “selection” rule (selection – taking one from many = removing others). Again, you are not asking how to justify the creation of OUR universe( that would be natural for one going from nothing to the Universum), you seek the justification of removal for the others. So we are on the same page.

But: if we go in the opposite direction, from the Universum, then any REMOVAL adds new information and hence is a subject of Occams razor. Going from nothing to the Universum we must justify any addition, going back we must justify any removal. You mentioned Occams razor and on the very next step started inventing NEW entity which you call a “selection rule”. Do you agree with my logic?

So Occams razor is the very reason I believe other Universes exist.

I still do not see how the concept of a DESCRIPTION of a world is converted into the WORLD itself.

It is not CONVERTED. It IS WORLD.

You know, there are some naïve questions like “what is space?”. People tend to ask such questions because of the intuitive conception that if something is not made of something then it is void and collapses. So the most satisfactory answer would be “space is made of spacions”. “Ah, yes, it makes sense”. Of course, after a while they would start wondering what spacions are made of.

We always had a situation that something was made of something: molecules of atoms, atoms of elementary particles, then came quarks, now we expect them to be made of strings. We so got used to it that we are not psychologically ready to the fact that in TOE that infinite reduction MUST END.

Say, you are looking at the page with few beautiful equations. These TOE equations describe, say, some function Q in some quaternion-valued space and some equations that function Q obeys. All other entities: time, space, gravity, particles, emerge from these equations.

But you start to worry. this is just an equation What makes it real, you ask yourself. You are desperately trying to find a magic wand which would touch the paper with formulas and the formulas will start to “live”. You are not satisfied with the fact that this IS TOE. If I would say that the reality is made of “realityons”, obeying these formulas, you will be satisfied, right? If I would say that there are JUST formulas, you will be not. You will be even satisfied if I would say that these formulas are emulated on some supercomputer. Because again it shows that there is smoothing behind the curtain – realityons, computers, or something.

Max Tegmark article is so shocking because he insists that there is nothing behind the curtain – no spoons, no realityons, no supercomputers. Fundamental notions are fundamental only if they do not consist of anything. Fundamental notions do not need any agents to be “incarnated”. Otherwise they are not fundamental and the theory is not a TOE.

The mathematical framework is eternal(B) and exists "forever"(Dmitry67 - wrong, because forever is (A) category). It does neither exist "in time(B)" nor "in space". But a universe can be created out of "something" and eventually it can fade away(A). Therefore the lifetime(A) of a universe could be finite(A), whereas the lifetime of the corresponding mathematical framework is certainly not(B) (homework: when will the prime numbers die?)

That logic is wrong. Time is a notion INSIDE our Universe. Other universes can have no time (euclidean space) or might have multidimensional time, or something else. Abstract world of Universes does not have time defines.

You are mixing 2 things:
(A)“eternal” as “lasting for eternity of time” = “being infinite in time”
(B) “eternal” as “existing independently of time” = “something to which a concept of time is not applicable”
In your quote I put marks (A) and (B) showing how you mix these notions. In the highlighted part you compare (A) and (B) which is incorrect.