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Théo Le Bret

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Beyond the Standard Model: The String Controversy

Posted: 03/07/2012 00:00

In a couple of days, the final results on the search for the Higgs boson at CERN will be publicised, so in the meantime, I would like to dwell a bit on what comes after. Indeed, if the Higgs is found, this will only have confirmed, once more, that the Standard Model of Particle Physics was right, and was able to predict the existence of a new, exotic particle.

But the Standard Model has been around since the 70s, and, for all its predictive power in particle physics, it suffers from major shortcomings: for instance, it becomes completely inappropriate when dealing with gravity. For this reason, most of the work of theoretical physicists for the last 40 years has endeavoured to find a deeper, all-encompassing theory, a Grand Unified Theory (a GUT...).

One of the serious contenders for the title today is superstring theory, a rather elegant theory that postulates that all known phenomena are actually manifestations of the vibrations of microscopic strings (too small to be observed with our present technology), in nine or 10 dimensions of space.

Fascinating on a purely aesthetic level (as Brian Greene puts it, the Universe of string theory is "nothing but music"), this theory has also sparked a truly interesting controversy in the physics community, best illustrated by the publication in the past decade of books such as The Elegant Universe (Brian Greene) or The Cosmic Landscape (Leonard Susskind) on the "pro-string" side, and The Trouble With Physics (Lee Smolin) or Not Even Wrong (Peter Woit) on the other side (Greene's and Smolin's books especially provide a good, balanced overview of the subject).

Indeed, string theory today occupies a rather unique position in the world of theoretical research: it has, for nearly 30 years, concentrated the efforts of hundreds among the brightest physicists of our generation, and yet has still, as even string theorists themselves admit, not been formulated definitely in the form of a unique set of equations, making equally unique (and falsifiable) predictions, which is how most scientists define a physical theory. In fact, the name "string theory" is somewhat misleading, in that the "theory" today is more of a set of intuitions and ideas on what the end product may look like (although it must be conceded that even in its incomplete form, some rather interesting predictions have been extracted from it, such as those concerning black-hole entropy).

This curious state of affairs has led scientists to adopt different attitudes towards string theory: some claim it is "not even wrong", in that it can, in its current form, neither be proved nor disproved using experimental data, while others believe that eventually a unique theory will emerge, making predictions about our world, but that this would necessitate a better understanding of the theory than we have today.

An even more extreme attitude (though more marginal) is that string theory is right, but that humans are simply not clever enough to grasp it fully, the argument being that if you asked a dog to understand even rudimentary physics, this would prove beyond its intellectual means, so that in the end there is no reason why the human mind should not possess similar limits in understanding the physical world.

This last example is of course quite extreme, but usefully illustrates one of the most common reproaches made to string theorists: they have come up with something that is nothing more than an interesting hypothesis, and when they find that this hypothesis leads to unmanageable equations, they try and change the "rules of the game" rather than admit they have hit a dead end, which raises the question as to whether or not string theory may actually be damaging to science.

Indeed, although the idea that string theory will eventually prove beyond the grasp of humans is not one shared by the majority of the string community, the fact that some scientists are in such awe of their own creation that they are willing to believe it true but ineffable does reveal an alarming streak of fanaticism in this area of research.

But, in the end, what must be borne in mind is that the over-confidence of some string theorists is simply the result of their brainchild being "the only game in town" (or if not the only one, certainly the most popular), and unfortunately, as Lee Smolin argues in his book, this has got more to do with academic sociology than science...

 
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In a couple of days, the final results on the search for the Higgs boson at CERN will be publicised, so in the meantime, I would like to dwell a bit on what comes after. Indeed, if the Higgs is found,...
In a couple of days, the final results on the search for the Higgs boson at CERN will be publicised, so in the meantime, I would like to dwell a bit on what comes after. Indeed, if the Higgs is found,...
 
 
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03:19 AM on 07/06/2012
What's with all the rage against string theory? It's a harmless, if highly entertaining, mathematical structure that fascinates a lot of very smart people. Even if it had absolute no significance for physics, it should be thoroughly explored.

Having said that, it may have quite a bit of significance for physics. Maybe not as a theory of everything, quite yet, but it's certainly an interesting stepping stone on the way to such a theory.
04:09 PM on 07/10/2012
I don't know about "rage", but the debate is an extremely important one. Falsifiability requirements are one of the fundamental pillars of the scientific method, to abandon them is to abandon science.

I have no objection to all those very smart people spending their days trying to work something out that they have not quite managed to do yet... and they can keep doing that as long as they like so long as they don't try and change the definition of what "worked out" means to shift the goalposts and claim success when they have not succeeded.

Success is formulating a theory that makes real, testable, falsifiable predictions and thus demonstrates real explanatory power... and then following through on the testing and figuring out if they are right or wrong. That is the goal line and you do not get to move it and still call yourself a scientist. You abandon the falsifiability requirements of science and you have just switched to doing religion instead.
09:15 PM on 07/10/2012
"Falsifiability requirements are one of the fundamental pillars of the scientific method, to abandon them is to abandon science. "

String theory is clearly falsifiable, so that's not even an issue.

"so long as they don't try and change the definition of what "worked out" "

String theorists make no such scientific claim. So, that, again, is nothing to be concerned about.

"Success is formulating a theory that makes real, testable, falsifiable predictions and thus demonstrates real explanatory power."

And string theory is not a theory but a model that people work on because it has some really interesting properties. It does not have any explanatory power right now. So that's all pretty dandy, too.

"That is the goal line and you do not get to move it and still call yourself a scientist. "

Working on far out models does not exclude you from being a scientist. If it did, Einstein would have given up being a scientist when he worked on general relativity.

"You abandon the falsifiability requirements of science and you have just switched to doing religion instead."

Very good. Now name a string theorist who did. Quick!
batguano
As Long As Grass Grow, Wind Blow & The Sky Is Blue
10:14 PM on 07/05/2012
Would someone please comment on this linked theory and its relation to the Higgs Boson, Higgs Field, and current related CERN/LHC hoopla. Thanks.

http://www.higgs-boson.org/
01:31 AM on 07/06/2012
Nothing particularly new here, as far as I can tell. If we correct for the fact that the diagrams are wrong, it looks like an amateurish attempt at a lattice defect density description of gravity.

I had a sixty second introduction to one of these models in my introductory class on general relativity decades ago. That class was held by a solid state physicist and because defects in lattices are a bread-and-butter phenomenon in solid state physics, he was personally interested in defect models. Other than that, they are probably mostly ignored by most classes on GR. Having said that, the mathematicians have explored these concepts in differential geometry for a long time, see e.g.

http://www.sciencedirect.com/science/article/pii/0020722581900732

for a professional treatment. No need to go to the amateurs here, the professionals have been on top of this thing forever. Without success, as you can tell from the fact that the problem is still far open.

The most significant problem with the naive defect picture is that is uses a metric dependent background field, and is therefor not Lorentz invariant. The correct general relativistic version of these seem to re-appear in loop quantum gravity in form of spin networks and spin foams... which seem to preserve background independence and Lorentz invariance.

Hope this helps.
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CSDofNM
I speak lolcat
03:07 PM on 07/05/2012
The problem with string conjecture (not yet a theory) is the math. Math with infinite initial conditions, math with infinite solutions, math with infinite NP complete compute time. String conjecture is nothing more than a hobby for itinerant mathematicians. It has no validity when compared to experiment. So it can't even be wrong, much like painting top fuel dragsters in your garage can never be wrong. It is a hobby that will never go anywhere.

Yet the conjecture of distributed strings, in an 11 dimensional universe, is the closest thing to a Grand Unified Theory. 11 dimensional M-theory is so universal it has eaten all the other string conjectures.

There again is the problem. Being everything to everybody, it ends up being nothing to anyone.

We have known physical constraints. Scales of forces, etc. Any conjecture that does not START with those is really just counting angels on the head on a pin. We have 1/R scale invariance, and the scale inversion between EM and gravity as compared to strong and weak forces. Throw the Higgs field in there and you have a nice soup. But until and unless you use it to make testable assertions about the real world, it really is little more than "World of Warcraft" for mathematicians. You may become a 17th level mage, but your spells don't work in the real world.
07:39 PM on 07/05/2012
That string theory is so "universal" is not a given. We merely don't know what other restrictions it obeys that have not been discovered, yet. For all we know string theory could very well be a unique object or even an empty set.

The string landscape is an argument from ignorance.
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CSDofNM
I speak lolcat
08:11 PM on 07/05/2012
String conjecture is nothing but "World of Warcraft" to amuse mathematicians. Empty set seems right.

If you don't construct your calabi-yau manifold correctly, you'll never get to your string landscape, much less Narnia.
12:26 AM on 07/05/2012
I keep looking at the ICHEP 2012 presentations about signs for beyond SM physics... so far... nothing, unless I missed something.

:-(
06:36 PM on 07/04/2012
Hold your horses... what comes after the Higgs is, with pretty high probability, not string theory but something along the lines of supersymmetry.

String theory, as beautiful as it is mathematically, is simply an "it's not even wrong" kind of affair, still. There are, of course, very serious theoretical charges against it. For a model that supposedly can deal with quantum gravity, which may not even exist, it relies very heavily on pre-geometry, which any TOE supposedly needs to be able to explain from first principles as an effect, rather than use as a starting point to describe itself. So there is a rather curious inconsistency in the very structure of string theory, already.

The safe bet, at this point, is to wait for the full LHC data set. If it contains signs of supersymmetry, then the program of real physics will continue along the lines of standard model extensions, and unless string theory, or any other similar model can produce the complete spectrum of the standard model from first principles, it will stay just that... not even wrong.
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CSDofNM
I speak lolcat
03:10 PM on 07/05/2012
No supersymmetric particle has ever been discovered. A real problem for supersymmetric theory, as the lower level particles should be just a plentiful as our normal ones.
BEEP! End of theory.
07:26 PM on 07/05/2012
"A real problem for supersymmetric theory, as the lower level particles should be just a plentiful as our normal ones."

Huh? Why would that be? If the energy required to make a real SUSY particle is above the energy of our largest accelerator, we can't make any. That't just below the TeV scale right now, which means it only excludes sub TeV SUSYs. If the cross sections for virtual SUSY particles are small (because their masses are large), they won't show up as corrections in experiments until large amounts of data have been collected. LHC hasn't done that, yet. The lowest energy SUSY candidate is a WIMP... it won't even show in your detector, except as missing ET (and if you think that means extraterrestrial, you won't even have to comment, again). It will, on the other hand, have been produced copiously during the very early big bang and have hung around as... you guessed it... dark matter.

:-)
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06:54 AM on 07/04/2012
  I understand thoroughly  what you are trying to communicate about being so close to a phenomenon that you can't recognize it.   When conducting my research on the nature of leadership,  all the interrelated data I had accumulated predicted as it was supposed to predict.  Yet, I kept missing seeing something and I didn't know what it was. I went back to the study of great physical scientists and their failed counterparts in the social sciences (social studies).  I tried to place myself in Einstein's mental state and processes.  I kept persisting.  Then one day it hit me like a flash of light.  Leadership must have a constant (the mission statement) as the universe has a constant (the speed of light),  Leadership is the process that is the basis of all human interaction and performance.  From that insight, I developed the unified theory of leadership that pulls together the ingredients for all human existence.  I succeeded for human organizing as Einstein succeeded for nature's organizing.
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Gas-Bag
There's nothing endearing about perfection.
05:10 PM on 07/04/2012
Have you authored a manifesto yet :-)
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01:14 AM on 07/05/2012
  My book is coming out soon.
06:36 PM on 07/04/2012
You do not understand correctly.

:-)
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critterzdad2
Even a stopped clock is right twice a day.
06:38 AM on 07/04/2012
A string theory? Never pull on strings... its never what it seams to be!
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07:00 AM on 07/04/2012
My version of the theory is that strings in lingerie are very predictable.
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critterzdad2
Even a stopped clock is right twice a day.
07:08 AM on 07/04/2012
Yep- any underwear is bound to have a string attached and a theory of what goes where isn't far behind how much!
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06:24 AM on 07/04/2012
  There are lessons in history. Even after the Greek Aristarchus had envisioned a sun centered universe, about a 130 years later the great Ptolemy proved the validity of the fact that the earth is the center of the universe.  The geocentric universe held captive the human imagination  until the 1500s when Copernicus provided evidence for a sun-centered universe. Let's hope that string theory does not  become an unexamined truth that stops human imagination for hundreds of years.
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Drg40
Representative Democracy is all we have.
08:26 AM on 07/04/2012
But know we know, don't we, that the Sun is not at the centre of our universe - in your terms - but almost precisely at the centre of our solar system. That the centre of the observable universe is not at an identified body (but since it stretches evenly away from us in every direction the earth could be consided at the centre) and that the centre of the universe as a whole is at an unknown location. We also know that the food you eat is grown by farmers, who mostly go by the way the sun goes round the earth to find the best day for planting. So the best you can say about who goes round what and why is to ask what the info is needed for.
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01:51 PM on 07/04/2012
   Such brilliant analysis deserves more than just a F&F.  it calls up another member to fill my cabinet for administering our defaulting nation. You could rapidly become a great cabinet member of my administration.  Your leadership would make my presidency  ever more able and prudent as my other staff and I learned and developed with your growing competence and confidence.  May your days, weeks and years ever be more challenging an enriching and productive and rewarding. Warmest regards.  TML
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Paul Wagland
Resistance is fertile
05:04 PM on 07/03/2012
I think the 'physics for dogs' analogy is interesting. It might not be human intelligence that is holding is back though, it might be the language in which we describe the problem: the language of mathematics.

This is known as linguistic determinism, essentially meaning our understanding of the world is limited by our capacity to describe it. http://en.wikipedia.org/wiki/Linguistic_determinism
06:38 PM on 07/04/2012
If that hypothesis would hold water, it should be able to produce, at least, a single working example to support it. Not holding my breath that it will. But then, a new religion is born every day and they all garner their share of followers.

:-)
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Paul Wagland
Resistance is fertile
07:16 PM on 07/04/2012
I'm no expert on linguistics, but one example I know of would be that people in different cultures, who have different words for colours (and indeed different perceptions of what constitutes each colour) will see a different number of 'bands' in a rainbow. For example in English we describe seven bands (red, orange, yellow, green, blue, indigo, violet). Other languages may describe indigo and violet as one colour, or perhaps three. The fact is that rainbows are a spectrum, without any distinct bands. So language controls our perception. It's a theory, that's all I'm saying!
01:33 PM on 07/03/2012
Science has always been about coming up with models which best fit the observations, ready to be superseded by the next model which comes along. Also a lot of science has to have an element of philosophy in it, whether it is the definition of life or the nature of the universe. Theoretical physics, is exactly that so will always be philosophical and will always have newer and (hopefully) better models to explain the observations. 99.9% of scientists know that their theories are there to be knocked down and welcome constructive debate in their fields.
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08:33 PM on 07/04/2012
Part of the problem is that it took 40 years to find that you can't knock down the Standard Model of particle physics.

String theory begins right where that model ends. So it might take a while until we know whether or not it can be knocked down or not.

In other words: those 99.9% may not apply within the community of string theorists. For sheer lack of knocking power.
09:42 PM on 07/04/2012
Nonsense. The standard model does not have any answers to CP violation, which had been discovered before the standard model was even formulated. There are, at least, half a dozen serious problems with the standard model now.

What comes after the standard model are the supersymmetric extensions of the standard model. You don't need any string theory for that.

Diogenes, get a better barrel. One that can hold a physics library.
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CSDofNM
I speak lolcat
03:20 PM on 07/05/2012
There is no such thing as 40 years of the Standard Model.

There is an equation. Always wrong somewhere, always backfitted to data.

The Standard Model of December 1st, 1950 bears little resemblance to the standard Model of December 1st, 2010. And that one bears little resemblance to the one of December 1st, 2012.

It is an equation, that gets terms added to it and removed from it every week. It is astoundingly accurate in matching our experiments (to 17 decimal places in many cases). It is absolutely incompetent in predicting anything about gravity, or the source of mass. Higgs equations are being grafted on, and tested, but it still won't be predictive.

Mathematical models are very good for looking backward at what you already know. String conjectures show us we know nothing, and can test even less.

No, you can't knock down the Standard Model of Physics (version 7.5.2012), because version 7.12.2012 will have new terms that correct for whatever you found.

And that is a beautiful thing, called progress, because science improves its understanding.
lastpost
see biography
01:07 PM on 07/03/2012
"major shortcomings"
Stephen Fry postulates that proof of comprehension is confirmed, on creation of devices functioning though the application of those theories previously proposed. Except that we have the grandfather clock. But what is gravity exactly?

"a Grand Unified Theory (a GUT...)."
Presumably ratified on the initiation of a gut reaction?

"on a purely aesthetic level"
if all this is indeed possible, why classify “god” as being an obviously preposterous possibility?

"a set of intuitions and ideas on what the end product may look like"
Given its mooted that believing it makes sense, reveals a lack of understanding regarding the implications. Do humans have minds of a form capable of such envisionment?

"it can, in its current form, neither be proved nor disproved"
Watch out then. For the rise of Stringists and Athestringists.

"a better understanding of the theory than we have today."
If observations do not conform to the theories devised. Maybe those notions are ill-conceived.

"whether or not string theory may actually be damaging to science."
What’s damaging to science is mistaking expertise for infallibility.

"some scientists are in such awe of their own creation"
it might as well be a religion? That can come from not daring to challenge books.
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CSDofNM
I speak lolcat
03:41 PM on 07/05/2012
What are the major shortcomings of your religious theory? Can't name them? How about racism, masculism, and infallibility? Got any more? Your religion is a bad theory with explicit warnings not to put it to the test (because it will fail).

GUT reaction? So little confidence in your religion you have to take words out of context? Acronym. Look it up.

God is not a preposterous possibility. A God that intervenes, yes. One who set the rules for the Universe, maybe not. But you would never calculate those likelihoods, much less admit they are so very small.

Intuition on the end result implies that one must model the Universe, then improve that model. You don't. Your model is the mutterings of goatherders from 6,000 years ago when they were still Egyptian slaves. A lot has happened since then.

You are equating your belief in a God to string conjecture, neither provable nor disprovable. Good job!

Ill-conceived notions which get modified with new evidence are better than ill conceived beliefs that never get updated.

Science isn't infallible, and never claims to be. It's predictions are right 99.999999999% of the time, while yours are less than 1% of that.

No, science isn't a religion. Tenets change. Evidence is acquired. New ideas are accepted.

Reread Matthew 25:34-40, John 14:12, and John 8:32-47. Realize you are COMMANDED to LEARN the truth, heal people better than Jesus, and take care of those worse off than yourself..
03:28 AM on 07/06/2012
Wow... someone is really angry now. Are you going to give him a good beating the next time you see him?

:-)
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jessjesskk
Benevolent Zombie Power
09:41 AM on 07/03/2012
I recommend to all interested to read Brian Greene's books. Beyond being clever, he is a very good and interesting writer.
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07:04 AM on 07/04/2012
Indeed. And he is still greene. Imagine when he gets ripe!
SelfAwarePatterns
seek truth; question everything
02:37 AM on 07/03/2012
It seems to me, as a layperson, that string theorists are doing philosophy. Now, I personally don't see anything wrong with that, but I do wonder if it should be called science, at least until it becomes testable. Remember that the first atomic theory was put forth by Greek philosophers who were conducting, at the time, untestable metaphysical reasoning.

On a side not, it's curious how scornful many (although certainly not all) theoretical physicists are toward philosophy. It's as though they know that some of them are perilously close to what philosophers do and feel the need to distance themselves.
06:43 PM on 07/04/2012
Why would it be philosophy? A philosophy is something you are supposed to be able to live by. Someone should show me a person who lives by the principles of string theory.

Philosophies are, of course, a dime a dozen. Physical theories, on the other hand, are rare. We don't have more than a handful of them. String theory, not being one of them, is one of hundreds of models that have been explored to see if they have a reflection in nature. String theory is testable and it is being tested as we speak. The initial signs seem to show that it will fail spectacularly, and that will be the end of it. Can't say the same things about monads...
SelfAwarePatterns
seek truth; question everything
07:40 PM on 07/04/2012
I think you're thinking of moral philosophy or maybe epistemology, which are only two branches of philosophy. Unless it's testable, I would say string theorists might be doing metaphysics, another branch that often tackles subjects like free will.

I've read and heard conflicting statements from physicists about whether or not string theory is actually testable. Most non-string theorists seem to doubt that it is. From what I understand, it's actually a collection of theories. Maybe some are testable and others not?
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08:36 PM on 07/04/2012
I think that the greeks who invented the idea of atomism were actually quite lucky as far as sound theoretical underpinning and experimental tests of their theory are concerned. It took barely two millenia. String theory might have to wait a lot longer than that.
10:00 PM on 07/04/2012
And you would know this... because?

:-)