LHC - the last chance for all theories of everything?

Dmitry67

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

marcus

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

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

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

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

marcus

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

tom.stoer

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 dont need a selection rule.

Vanadium 50

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

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.