What about the absence of a unified field?

[marcus]

Fredrick your post is too abstract. About "belief". the rightest theories we have are known to be wrong and are simply not believed.

Gen Rel predicts with unprecedented and exquisite accuracy. As a theory of gravity it has no peer. It rivals QED in the precision with which it is able to predict the rate that a pair of neutron stars in tight orbit will radiate away gravitational energy in the form of gravity waves.


But everybody knows that Gen Rel is wrong! Even I am not so credulous as to think that Gen Rel is a correct theory. Indeed this is obvious, because it breaks down at the big bang and at the center of black holes----calculating with Gen Rel in such circumstances results in singularities, which indicate failure of the model.

I find it inconceivable that this situation would not be duplicated each time the fundamental theories of science are replaced by new, more accurate and more powerfully predictive ones. Everybody will know that these new theories are wrong, and will not believe them.

Maybe verbal models can be correct. I don't know about that.
but mathematical models, in science, are customarily known to be wrong and one uses them only in limited circumstances where they'r applicable and one hopes to see them eventually replaced by better

So, yeah I see no obstacle to humans getting a mathematical theory that combines Gen Rel with Std Muddle and outperforms both in making accurate predictions.

I think humans will be able to do that. But it won't be a "THEORY OF EVERYTHING" because that phrase is just poetry and baloney and hype. Merely including gravity with the other "forces" of particle physics is certainly not EVERYTHING. Starry eyed people can rhapsodize about that in order to sell books.

So I think your thread-start premise is wrong. Nothing can be concluded from the ABSENCE of a theory unifying particle physics and gravity. It is just the next thing on the agenda. No danger of that being a final theory. Not a chance. It is not a big deal that nobody has seen how to take that particular step as yet.

I think the way humans will get a unified theory is by first getting the theory of spacetime right. that is what Loop QG is trying to do.
Then once there is a decent quantum theory of spacetime, they will put matter into the picture.

It is like being in 1850 and Maxwell has not figured out how to put Electricity together with Magnetism yet. You can't go and draw grand portentous conclusions from the fact that there is no "unified" theory.
Just wait. It will come. Electricity and Magnetism will be unified and then, guess what, there will still be more stuff to do and improvements to make.

So with us now. People will put quantum spacetime together with quantum fields and particles.

Then it will be a little less mysterious how it happens that "matter tells space how to curve" and curved space tells matter how to flow.

It will be like when Maxwell's equations happened.
And like then, no big deal and plenty more to do in getting to know nature better.

Well this is an opinion piece, one person's view. You hospitably said "mi casa es su casa" about this thread, so hope it accords with your wishes.

 

[selfAdjoint]

But everybody knows that Gen Rel is wrong!

Dyson doesn't admit it.

 

[Kagmi]

General relativity seems to work just fine, I think all we need is a modification of the way either space or particles work at quantum scales. M theory is, in my opinion, the most promising candidate at the moment.

 

[marcus]

Dyson doesn't admit it.

I read Dyson's recent article in NY Review of Books (found it online!)
and it seemed to me he hedged

IIRC he was saying not that Gen Rel is OK but only that it is OK in its range of applicability, nothing better in sight.

he didnt seem aware of LQG and its removal of the classical singularities

he was addressing string theory and all the talk about gravitons---string theory predicts gravitons etc etc.

he was skeptical of gravitons---said we'd never be able to see one, why even suppose they exist?

from that POV then sure, just stick with old Gen Rel and be content. have one theory for gravity and another for particles and fields. The underlying sense there is you can't do any better

But I think Dyson would readily admit that Gen Rel is unsatisfactory because of the singularities. He may even have acknowledged that in the NYRB article----I can't remember whether he did or not----though that was a non-technical piece of writing for general audience and maybe discussing singularities would have been a bit too technical in that context.

 

[Kagmi]

I'm just being introduced to the theory of LQG, but I have long been a proponent of M theory (or superstring theory, or whatever you want to call it) because of the mathematics. I read in an earlier post a question about the unification of gravity and electromagnetism, and would like to note that part of the basis for M theory's extra dimensions is the fact that, when extended into a fifth spatial dimension, the equations of gravity yeild the equations for electromagnetic force. As for never detecting a graviton, I find it hard to believe that, if they exist we will never have instrumentation sensitive enough to detect them.

 

[marcus]

... As for never detecting a graviton, I find it hard to believe that, if they exist we will never have instrumentation sensitive enough to detect them.

I'm in strong sympathy with the attitude you express. Never say never.
But this is how I remember Dyson's NYRB article. There should be a link to it somewhere so we can check if he really said that or if he qualified it substantially.

Why would Dyson have been pooh-poohing gravitons? I think it is part of a contemporary trend to debunk string hype---a trend that one sees, for example, in the recent article From Gravitons to Gravity: Myth or Reality? by Thanu Padmanabhan.
It is on arxiv, so one finds it easily by author search.

the basic message is "let's not attribute so much importance to the string claim to include gravity" An equation for something that might be a graviton comes out of string math, but gravity is more than gravitons, or so it is said, and maybe just having gravitons in a fixed background geometry does not accurately reproduce gravity. Anyway, so the story goes.

Dyson's particular contribution to the general message is to cast doubt on the significance of gravitons: to the extent they can be said to exist (as conjectured quanta of the gravitational field which no one yet knows how to quantize) one can expect individual gravitons to have much lower frequencies than, for instance, light. Much lower energies than those of detectable quanta of radiation.

No one, so far, has ever detected a quantum with the frequency MIDDLE C.
You can think about the processes that are expected to produce gravity waves. think about the expected wavelengths, and frequencies. The energies are many orders below those of, say microwaves. Would you expect to detect a quantum of microwave?

I am paraphrasing Freeman Dyson's message to readers of the New
York Review of Books. It is not a technical audience and he is choosing to communicate what he can to them. the point is perhaps not terribly significant or decisive. What it communicates is more Dyson's perspective or attitude.

I don't offer his opinion as my own. I would not want to say "never" detectable. but look at the figures. Micron light has about 1 eevee quantum energy. Just as an order of magnitude. A manmade instrument can detect an individual 1 eevee photon. there are photon counters at roughly this level----you get to hear the click.

A gravity wave detector is say, 10 meters long, and it detects a gravity wave with characteristic wavelength 10 meters. what is the energy of individual quanta of this wavelength? Ten million times weaker than 1 eevee.

I don't think anyone has imagined a way to detect an individual photon with energy of one ten-millionth of an eevee. so is it reasonable to imagine detecting a graviton with such small energy, if one cannot even picture doing it with a photon?

Maybe Dyson's point is not so strange as it originally seems.
In any case, if you want to read his NYRB article I will try to help find it on the web. Might be a simple google search. Or self-adjoint may just happen to know.

 

[Fredrick]

Picture

In the New York Times Science section of today (3-29-05) I read about the collision of gold nuclei in the Brookhaven National Laboratory. Here is a picture of the result:
http://www.physicscentral.com/pictures/images/pictures-00-4s.jpg
and the abstract can be read at http://arxiv.org/abs/hep-th/0501068

This is powerful imagery that seems to support what I am saying about an empty center at the emergence of the universe. Dr. Horatiu Nastase describes in the NY Times article that "(t)he collision of gold nuclei produce matter as it existed shortly after the Big Bang."

In as far as a theory of everything is concerned I could not ask for a better image. It does not mean absolute evidence, but it is nice to deliver a picture next to the words.

 

[marcus]

In the New York Times Science section of today (3-29-05) I read about the collision of gold nuclei in the Brookhaven National Laboratory. Here is a picture of the result:
http://www.physicscentral.com/pictures/images/pictures-00-4s.jpg
and the abstract can be read at http://arxiv.org/abs/hep-th/0501068

This is powerful imagery that seems to support what I am saying about an empty center at the emergence of the universe. Dr. Horatiu Nastase describes in the NY Times article that "(t)he collision of gold nuclei produce matter as it existed shortly after the Big Bang."
...

nice picture
the superficial similarity to an eyeball was not lost on me

it seems to me I was discussing that RHIC result somewhere else, maybe a thread here at PF
the similiarity with "matter as it existed shortly after the Big Bang"
is a similarity of temperature

Oh, you mentioned that part of the picture is missing, so there is an empty part of the picture in the middle.
I suppose that part is the tube where the particles collide (so there cannot be any detector there) the image would only be generated from what happened in the ringshaped space around the tube where they could position detectors.

correct me if I'm wrong but it seems that if they could situate detectors closer into where the collision occurred, then they would see a whole lot more activity not included here, but this is a great picture already (even with the missing detail in the middle)

does anybody know more about the RHIC (relativistic heavy ion collider) "fireball"

 

[Haelfix]

Err the reason people like the concept of the graviton is it more or less reproduces linearized GR exactly. Write down the field theory for a massless spin 2 particle, poof Einsteins eqs. It would be one of the fantastic cruelties of nature if that turned out to be coincidental.

String theories graviton is a little more complicated, its more of a SUGRA GR, eg gravitons coupled to some extra fields (like the dilaton) etc

Now you can argue that there should be extra stuff, presumably stuff that makes the background make sense, and all that is fine and good. But as an effective local field theory, it seems to me that its a damn good indication that people are on to something.

 

[marcus]

Err the reason people like the concept of the graviton is it more or less reproduces linearized GR exactly. Write down the field theory for a massless spin 2 particle, poof Einsteins eqs. It would be one of the fantastic cruelties of nature if that turned out to be coincidental.

String theories graviton is a little more complicated, its more of a SUGRA GR, eg gravitons coupled to some extra fields (like the dilaton) etc

Now you can argue that there should be extra stuff, presumably stuff that makes the background make sense, and all that is fine and good. But as an effective local field theory, it seems to me that its a damn good indication that people are on to something.

hi Haelfix, we had a discussion about this back in November, around the paper by Thanu Padmanabhan
https://www.physicsforums.com/showthread.php?t=44414

selfAdjoint started the thread, which was called
String Gravitons Yield GR. NOT.

Here was the first post of the thread:

This paper does a lot of testing of different kinds, and concludes that the string theorists assertion that the graviton reproduces the physics of GR in flat spacetime is a myth.

Haelfix, I personally am not challenging your remarks, which seem mainly intuitive. But I would be interested to know your thoughts about the Padmanabhan paper.
Here it is:
http://www.arxiv.org/abs/gr-qc/0409089

 

[marcus]

here's a quote from the abstract of the Padmanabhan paper:
http://www.arxiv.org/abs/gr-qc/0409089

From Gravitons to Gravity: Myths and Reality
T. Padmanabhan

"There is a general belief, reinforced by statements in standard textbooks, that:

(i) one can obtain the full non-linear Einstein’s theory of gravity by coupling a massless, spin-2 field h_ab self-consistently to the total energy momentum tensor, including its own;

(ii) this procedure is unique and leads to Einstein-Hilbert action and

(iii) it only uses standard concepts in Lorentz invariant field theory and does not involve any geometrical assumptions.

After providing several reasons why such beliefs are suspect--and critically re-examining several previous attempts--we provide a detailed analysis aimed at clarifying the situation. First, we prove that it is impossible to obtain the Einstein-Hilbert (EH) action, starting from the standard action for gravitons in linear theory and iterating repeatedly.

This result follows from the fact that EH action has a part (viz. the surface term arising from second derivatives of the metric tensor) which is non-analytic in the coupling constant, when expanded in terms of the graviton field. Thus, at best, one can only hope to obtain the remaining, quadratic, part of the EH Lagrangian (viz. the Gamma² Lagrangian) if no additional assumptions are made. Second, we use the Taylor series expansion of the action for Einstein’s theory, to identify the tensor S^ab, to which the graviton field h_ab couples to the lowest order (through a term of the form S^ab h_ab in the lagrangian). We show that the second rank tensor S^ab is not the conventional energy momentum tensor T^ab of the graviton and provide an explanation for this feature.

Third, we construct the full nonlinear Einstein’s theory with the source being spin-0 field, spin-1 field or relativistic particles by explicitly coupling the spin-2 field to this second rank tensor S^ab order by order and summing up the infinite series. Finally, we construct the theory obtained by self consistently coupling h_ab to the conventional energy momentum tensor T^ab order by order and show that this does not lead to Einstein’s theory. The implications are discussed."

 

[Haelfix]

For technical reasons I don't like that paper, he keeps total derivatives here and there and there seems to be some issues with some of his math. I haven't looked at it since then but I was and still am a little skeptical.

It takes quite a bit to challenge 30 years of tried and true field theoretic results (note this has nothing to do with string theory necessarily).

 

[marcus]

For technical reasons I don't like that paper, he keeps total derivatives here and there and there seems to be some issues with some of his math...

Haelfix, thanks for the reply. You hear coffee-room stuff which I am always glad when you pass along.

What has struck me as odd is that no one seems to have written a paper replying to Padmanabhan. He is prominent in his field, so if there is something wrong with the math in that paper I would expect more than unpublished gossip to that effect. I am surprised no one has published their misgivings. Or if they have I haven't heard. I will do a citation check and see what "cited by" there are.

Nope. No one critical of the Padmanabhan paper has published anything citing it.

I guess you know: Ashtekar is editing a book to be published this year called "A Hundred Years of Relativity" and Padmanabhan is one of the authors.
The "Myth or Reality" paper will be apparently cited in Ashtekar's book because Padmanabhan cites it in his draft chapter.

 

[Fredrick]

Black hole

Oh, you mentioned that part of the picture is missing, so there is an empty part of the picture in the middle.
I suppose that part is the tube where the particles collide (so there cannot be any detector there) the image would only be generated from what happened in the ringshaped space around the tube where they could position detectors.

correct me if I'm wrong but it seems that if they could situate detectors closer into where the collision occurred, then they would see a whole lot more activity not included here, but this is a great picture already (even with the missing detail in the middle)

does anybody know more about the RHIC (relativistic heavy ion collider) "fireball"

Dr. Nastase states that a (mini) black hole may have been recreated.

 

[Fredrick]

Momentary nothing

I read it again in the New York Times science section this last week, that during the collision at BNL of two gold nuclei a momentary nothing - a fraction of a second in which nothing occurred - was detected before materialization of the new plasma became visible. I find this highly telling.

 

[mosassam]

Apologies for just butting in randomly (I wasn't sure where else to go). Just a quick question - can anyone tell me if strange attractors have their own, independent existence or are they always dependent on something? (or is this a stupid question?)

 

[Anonym]

In the eye of the ant beholder

Fredrick :” I never thought I would talk here about Adam and Eve, but when it comes down to order, then ordering is in question and it must be addressed. There are two versions of ordering and I mention it here because it brings us back to the reason of this thread, which is basically the question: Unification or not.

With establishing the story that god created Adam first and from Adam god created Eve, an ordering has been used in time. Not to dispell any person's belief that this is true, a different way of ordering exists as well. God could have easily created both Adam and Eve at the same time.

What is the difference between these two versions? The difference is the ordering in time, and the link that exists (or not exists) between Adam and Eve.

When god created Adam and from Adam Eve, god established a top and bottom, a first and last, an important and an unimportant aspect, or however you want to frame it. This way a version of ordering has been created that appears applicable to everything; and everything is linked to each other. I think that the truth is not that simple. What is most important for you, is not most important for me. What is the top for you, I regard as not that high of a standard, what is first for me, may be second for you. You may give importance to leadership, I want everyone to follow their own voice while being respectful to others' voices.

When god created Adam and Eve at the same time, god delivered two segments that may have a lot in common, but in at least one aspect both have nothing in common: on one level of separation there is no link. Ordering can still be applied but each has their own version of ordering, in which various segments have their own positions. The parts may, but whole picture is not based on ordering because it is based on two equals that are not identical. One can armwrestle and decide who will be the winner, but that does not deliver an order that is natural; it is an order of results only. In this version it is preposterous to mention one of the two as top and the other as bottom, because each is not organized according to the other's principle, but to their own. Same goes for culture. Cultures can never top other cultures as a whole, only in segments. What is great in Western society, may be dummm in other societies, and vice versa.

Sorry to bring a religious story (Adam & Eve) into a scientific/metaphysical thread, but I am using it because it is familiar to everyone (Christian/Jewish/Muslim or not). It delivers an order, which may have much appeal, but which is not the only way in which everything can be ordered. It lacks information; it lacks options that clearly exist. That's why we have different religions. Some have only one god, others have multiple gods, while there are also a lot of people who believe there's no god(s) at all. I know that nobody can answer that question for everyone, only for ourselves.”

Creating Adam and Eve was His last step. He worked hard five “days” before that.Moreover, before He started to work, it was T&V simultaneously. They may be considered as different and separated entities, but mathematically it is also possible to treat them as the same object, only conjugated to each other, and defined at the same point also in space, provided that the notion of the space-time continuum is well-defined.

Fredrick :“Can I ask you to reply to this message with regards to our thread: do you believe unification exists?”

Yes.

Fredrick :”or do you believe a separation of at least one level is the norm?”

No.The norm is defined as a single positive real number (measurable quantity).

In addition, I prefer to do math-ph exercises and let Him to decide.

Fredrick :” Again, the math is terribly simple, but it may give you a nice look at the prime number sequences that exist within the natural numbers, and how they are all connected.”

Sorry, I did not read your book, but if you call the natural numbers or any subsequence within the natural numbers the mathematics, you are deadly wrong. You apparently missed the last 3000 years of the physically relevant development in the mathematics. The physical picture behind the unification is beautifuly simple, but the mathematics involved is terribly complicated. Otherwise, how one may explain the beautiful complexity of the real world?

And now let us look again at the origin.

Fredrick :” I am going to give one example of a singular platform (our earth) with four active members (North, South, East, and West). Though the platform is (or appears to be) singular, these four active ingredients do not have a common thread; the platform is known, but does not contain unification.

East and West can go on forever in their direction, but some unification can be found in that they can cover exactly the same spots. Depending on your point of view, a single place can be East or West.

For such single spot, North and South appear to deliver the same set-up as East and West, but North and South cannot go on forever in their direction. When on the North pole, one cannot go further North. One cannot even go East or West on the North pole. There is only one direction on the North pole, and that is South. To unify North and South in absolute terms is not possible, while it appears possible for East and West.

These four directions contain a pair of opposition without the possibility of unification (North and South), and a pair of opposition in which unification appears very well possible (East meets West).”

You use the Euler’s parametrization to describe the 3-dim rotations. Why you do not consider the Cayley-Klein parametrization which is analytical? Since it looks to you too complicated to comprehend? The physical picture behind it is very simple: 3 continuous parameters define the direction of the axis of rotation and the pseudoscalar continuous parameter define the angle of rotation around that axis. I leave to you as exercise to find who is The Physicist behind that parametrization.

For everybody who with me: don’t be fantasioners. Three other fundamental interactions are still not unified since the proton is stable (it is the QM ground state of three bounded quarks). And the electroweak U(2;c)~U(1;q) is still only nearly adequate phenomenological model. And the “theory of everything” or the “final theory of everything” is obviously nonsense.

Marcus:” It would just be some theory. surviving by continuing to accurately predict the next accelerator experiment and the next astronomical observation,each day betting its life on predictions of microscopic physics and of cosmology-----and destined to eventually be shot down”

“The next accelerator experiment” is obsolete. The pulse compression will allow to perform the necessary verification/prediction experiments in microphysics as well as in cosmology on the laboratory tables of average universities.

Fredrick :”Before the Renaissance theologians and scientists were often one and the same people”

Long ago I had an interesting student. He had Ph.D. in theology and came from Vatican. He decided to know what physics is. He was 2-year undergrad. I asked him the basic questions in optics. He did not know the answers, but said that he was not able to imagine how difficult the study of physics is.

Marcus:” But everybody knows that Gen Rel is wrong!”

Who are these everybody, please? GR is the Chapter and the most beautiful chapter so far.

Fredrick :” The unity that existed no longer exists after divorce or death.”

I am divorced twice. Now my last X seems want the unification again (the same had happens also in the previous case). With respect to death I have no experience yet. And this is the reason why I am not “able to deliver evidence that unifies the forces in one field I will be the first one to cheer you on.” Simply I don’t want waste my time.

Daniel Gleekstein.

P.S. Thank you for your presentation. I should change my attitude to the philosophers. Please, send my best regards to your friend Karl.