The Trouble with Physics-Woit's review

[marcus]

The Trouble with Physics---Woit's review

Peter Woit has reviewed Lee Smolin's book The Trouble with Physics
http://www.math.columbia.edu/~woit/wordpress/?p=451

Also the article in 12 August New Scientist about
1. emergence of matter in LQG
2. recovering ordinary gravity---evidence of LQG's correct semiclassical limit
is available free online:

http://www.newscientist.com/article/mg19125645.800.html

The New Scientist article is called You Are Made of Space-time

Before, it was available only to subscribers. Good article, written by Davide Castelvecchi, a web-editor working for
the American Institute of Physics (publisher of Physics Today)

idea that matter arises from braids in geometry.

twists and tangles that can interact by mutually untieing each other and creating other knots and things like that.

 

[pelastration]

Thanks Marcus. Very interesting article

Also the article in 12 August New Scientist about
1. emergence of matter in LQG
2. recovering ordinary gravity---evidence of LQG's correct semiclassical limit
is available free online:

http://www.newscientist.com/article/mg19125645.800.html

Now to go one step further.
Quote for the article: "Smolin, Markopoulou and Bilson-Thompson have now confirmed that the braiding of this quantum space-time can produce the lightest particles in the standard model - the electron, the "up" and "down" quarks, the electron neutrino and their antimatter partners".

If the quantum space-time creates (by braiding) all fundamental particles, then they are all connected, and thus all matter is sitting on the background (quantum space-time). That means that gravity is not an independent force but the observable result of the dynamics of quantum space-time itself. When one braid moves that also influences the position of the other braids.

Next to that there are other ways how the quantum space-time can create unique combinations, in example not by braiding but by simple penetrations, which create locally multi-layered spots.

 

[marcus]

Glad you liked it!

that same New Scientist link also had a short news item about more evidence that LQG has the right largescale limit---that it does gravity.

The article is titled Supersizing Quantum Gravity
(I think "supersizing" means scaling up and looking to see that it matches Newton at large scale)
==quote from 12 August NewSci==
Supersizing quantum gravity

For loop quantum gravity to succeed as a fundamental theory of gravity, it should at the very least predict that apples fall to Earth. In other words, Newton's law of gravity should naturally arise from it. It is a tall order for a theory that generates space and time from scratch to describe what happens in the everyday world, but Carlo Rovelli at the University of the Mediterranean in Marseille, France, and his team have succeeded in doing just that. "Essentially we have calculated Newton's law starting from a world with no space and no time," he says (www.arxiv.org/abs/gr-qc/0604044)[/URL].

Newton's law of gravity describes the attractive force between two masses separated by a given distance. However, it is not so simple to measure this separation when space has a complex quantum architecture of the sort in loop quantum gravity, where it is not even clear what is meant by distance. This has been the biggest obstacle to showing how Newton's law can emerge from quantised space.

The naive way to measure length in quantised space is to hop from one quantum to another, counting how many steps it takes to reach the final destination. According to loop quantum gravity, however, the fabric of space seethes with quantum fluctuations, so the distance between two points is forever changing, and can even take several values at the same time.

Working with Eugenio Bianchi of the University of Pisa, Leonardo Modesto of the University of Bologna and Simone Speziale of the Perimeter Institute in Waterloo, Ontario, Rovelli circumvented the problem. The team found a mathematical way of isolating regions of space for long enough to measure the separation between two points. When they zoomed out and used this mathematics to look at space-time on much larger scales, they found that Newton's law popped out of their theory.

The calculation by Rovelli's team does not yet reproduce the full complexity of Einstein's general relativity, which also describes masses large enough to curve space appreciably. Their result does point in the right direction, however. Lee Smolin of the Perimeter Institute calls it a major step forward. "[b]Their work shows that loop quantum gravity definitely has gravity in it," he says. "It's no longer just pie in the sky.[/b][/color]"
==endquote==
[url]http://www.newscientist.com/article/mg19125645.800.html[/url]

 

[Mike2]

Thanks Marcus. Very interesting article

Now to go one step further.
Quote for the article: "Smolin, Markopoulou and Bilson-Thompson have now confirmed that the braiding of this quantum space-time can produce the lightest particles in the standard model - the electron, the "up" and "down" quarks, the electron neutrino and their antimatter partners".

If the quantum space-time creates (by braiding) all fundamental particles, then they are all connected, and thus all matter is sitting on the background (quantum space-time).

I have to wonder what the difference is between permanent particles and virtual pairs. Why is one permanent and the other temporary? Is information lost somewhere else (perhaps behind an horizon) forcing information storage in permanent particles to compensate for the loss?

 

[marcus]

I think that Smolin's book would have a case for diversified research strategy even if you don't assume that string is having theoretical problems.

Giving grad students more exposure to alternative QG approaches, and broader opportunity in what thesis topics they work on (even if as stopgap you have to connect to a different university to get a second advisor.)

Giving postdocs support to do what they want---based on trackrecord merit of the individual---not bound to a particular research project.

I think he's got a case regardless of the particular circumstances at present.
==============

Also I would say that the book is going to make background independent non-string QG approaches more visible and this can be purely positive, it does not have to be coupled with string crit.

You don't have to argue that string looks off tracky or cul-de-sacky just to make the point that some other approaches have gotten exciting lately and will get more notice with things like Smolin's book. It is not exactly teenage turfwar or football. Although that aspect, if not overdone, can add to the entertainment value.

===============

anyway Peter Woit's review naturally (and AFAICS fairly) brings out the string-crit aspect of Smolin's book---and for balance, as soon as I can get the book and read it, I am going to try to highlight the part of the message which is not critical of string but is merely positive to non-string QG.

the "what comes next" in the title ("The Trouble with Physics: the Rise of String Theory, the Fall of a Science, and What Comes Next")

what comes next could easily be the kind of 4D "string" theory that some Baez students are investigating. They don't shake and they don't have extra dimensions---it is not string theory in the sense of Witten-Knittin'---but it could be what comes next

and so could Freidel and Baratin and Starodubtsev stuff. Or Sundance braids in spinnetworks---the dancing octopods. Laugh at your own risk. Really All these approaches are manifestly BACKGROUND INDEPENDENT at no point do they require the choice of a geometry.

Having Smolin's book come out seems likely to open up the picture quite a bit and make all sorts of explicitly background independent approaches more visible---approaches not requiring the preliminary choice of a background metric, that is to say: a geometry---and approaches hospitable to a positive cosmological constant.

We'll see. In the meantime, I checked the general physics bestseller figures again. As of 10:30 AM eastern on Monday 28 August

Elegant Universe #3
TwP #6
NEW #9
Road to Reality #10
Brief History of Time #13
Warped Passages #18
Cosmic Landscape #74

the Kaku books I was tracking earlier were no longer showing in the top 100.

As of 9:40 AM pacific the next day---Tuesday 29 August

RtR #1
EU #3
TwP #5
NEW #10
BHoT #20
Warped Passages #27
Cosmic Landscape #39

 

[marcus]

I mentioned Peter Woit's review of Smolin's book in post #1
I should also give the link to Bee Hossenfelder's review
http://backreaction.blogspot.com/2006/08/lee-smolins-trouble-with-physics.html

and her interview with Smolin
http://backreaction.blogspot.com/2006/08/lees-comments.html

Peter's review has a lot of substance and quotes from the parts of the book that particularly interested him---mixed with thoughtful reflections of his own. On the other hand I think Bee, in her review, tries to give a balanced overall view of what the book is about. Both are good.

 

[CarlB]

Loved the interview with Smolin. Especially the part about hill climbers and valley crossers:

Lee: "Here is a metaphor due to Eric Weinstein that I would have put in the book had I heard it before. Let us take a different twist on the landscape of theories and consider the landscape of possible ideas about post standard model or quantum gravity physics that have been proposed. Height is proportional to the number of things the theory gets right. Since we don’t have a convincing case for the right theory yet, that is a high peak somewhere off in the distance. The existing approaches are hills of various heights that may or may not be connected, across some ridges and high valleys to the real peak. We assume the landscape is covered by fog so we can’t see where the real peak is, we can only feel around and detect slopes and local maxima.

Now to a rough approximation, there are two kinds of scientists-hill climbers and valley crossers. Hill climbers are great technically and will always advance an approach incrementally. They are what you want once an approach has been defined, i.e. a hill has been discovered, and they will always go uphill and find the nearest local maximum. Valley crossers are perhaps not so good at those skills, but they have great intuition, a lot of serendipity, the ability to find hidden assumptions and look at familiar topics new ways, and so are able to wander around in the valleys, or cross exposed ridges, to find new hills and mountains.

I used craftspeople vrs seers for this distinction, Kuhn referred to normal science vrs revolutionary science, but the idea was the same.

With the scene set, here is my critique. First, to progress, science needs a mix of hill climbers and valley crossers. The balance needed at anyone time depends on the problem. The more foundational and risky a problem is the more the balance needs to be shifted towards valley crossers. If the landscape is too rugged, with too many local maximum, and there are too many hill climbers vrs valley crossers, you will end up with a lot of hill climbers camped out on the tops of hills, each group defending their hills, with not enough valley crossers to cross those perilous ridges and swampy valleys to find the real mountain.

This is what I believe is the situation we are in. And-- and this is the point of Part IV -- we are in it, because science has become professionalized in a way that takes the characteristics of a good hill climber as representative of what is a good, or promising scientist. The valley crossers we need have been excluded, or pushed to the margins where they are not supported or paid much attention to.

My claim is then 1) we need to shift the balance to include more valley crossers, and 2) this is easy to do, if we want to do it, because there also there are criteria that can allow us to pick out who is worthy of support. They are just different criteria. For more on this, read Part IV or my Physics Today essay."

http://backreaction.blogspot.com/2006/08/lees-comments.html

My feeling on this is that neither QM nor special / general relativity are currently on the true mountain. If either of them were, then the mountain climbers would have already climbed it. Therefore, both QM and SR must be wrong. Unfortunately, when one states this to almost any physicist, no further conversation can ensue because almost all physicists believe that at least one of these two theories must be correct. And of those, there are a lot of people who believe that both are perfect.

Carl

 

[Chronos]

I agree. Perhaps neither GR or QT are complete, but still correct at the proper scales. It suggests a third component is missing. It would be interesting to see what remains between GR and QT when reduced to their respective boundaries.

 

[CarlB]

My guess is that both GR and QM suffer from the same problem, putting the abstraction cart in front of the reality horse.

The way the two theories are organized, one begins with very abstract principles (i.e. no preferred reference frames, equivalence principle, Hilbert space, gauge principle). From these one derives the conserved quantities and or symmetries (i.e. energy, charge, angular momentum). From these one derives the equations of motion (i.e. field equations, metric, Dirac equation, perturbation theory). This is exactly backwards, the equations of motion are closer to the structure of the world; "angular momentum" is just a convenient technique for solving a problem.

I'd rather see both theories derived from a common structure. Like Einstein, I'd expect that the structure would be geometric.

The only common geometric structure I can see is Clifford algebra or Hestenes' geometric algebra. There are now Clifford algebraic versions of GR that live on "flat" space (the Cambridge geometry group). The simplest wave equation you can write in a Clifford algebra is a generalization of the Dirac equation which makes it a natural basis for quantum mechanics. The existence of flat space gravity suggests that one should assume gravity is a force mediated by a particle on flat space (like all the other forces). This method has such power and speaks so directly to the equations of motion of the two theories that I really don't see why anyone would try to unify QM and GR on any other basis.

The other abstraction, Hilbert Space, can also be eliminated by using Clifford algebra. Instead of a QM formalism based on spinors or state vectors, one can use density matrices which are very natural in a Clifford algebra. These give a natural geometric interpretation that eliminates such unphysical nonsense as supposing that electrons come back multiplied by -1 when rotated by 2 pi. (That is, the density matrix representation of an electron does no such thing.) Sometimes it seems like I'm the only one who appreciates the density matrix formalism. It got talked about some in this forum: https://www.physicsforums.com/showthread.php?t=124904 , but I really need to write more about it. That discussion was about the problem of defining "A + B" where A and B are states rather than particular state vector representations of states. Since -B is just as good a state vector as B, one cannot easily define linear superposition on the states, just on the representations.

Carl

 

[marcus]

...We'll see. In the meantime, I checked the general physics bestseller figures again. As of 10:30 AM eastern on Monday 28 August

Elegant Universe #3
TwP #6
NEW #9
Road to Reality #10
Brief History of Time #13
Warped Passages #18
Cosmic Landscape #74

the Kaku books I was tracking earlier were no longer showing in the top 100.

As of 9:40 AM pacific the next day---Tuesday 29 August

RtR #1
EU #3
TwP #5
NEW #10
BHoT #20
Warped Passages #27
Cosmic Landscape #39

As of 11:20 AM pacific Wednesday 30 August, standings in the "general physics bestseller" list were

Trouble with Physics #2
Not Even Wrong #4
Warped Passages #9
Elegant Universe #10
BHoT #17
RtR #32
Cosmic Landscape #43
Hyperspace: A Scientific Odyssey Through Parallel Universes, Time Warps, and the 10th Dimension #47
https://www.amazon.com/gp/bestsellers/books/14560/ref=pd_ts_b_nav/102-4540543-7840144&tag=pfamazon01-20

in the entire physics list (which includes specialized textbooks)
TwP #3
NEW #5
https://www.amazon.com/gp/bestsellers/books/14545/ref=pd_ts_b_ldr/102-4540543-7840144&tag=pfamazon01-20

 

[selfAdjoint]

So the ST critique has legs. Sigh! You know I have never been part of this particular Wild Hunt, and I have a very bad feeling about what the upshot of all this is going to be. In a nation where interest in science is more and more a beleagered elite enthusiasm amid the rampant know-nothing populism, this year's science budget was a catastrophe for physics. What do you suppose next year's will be like when congesspersons can wave around copies of NEW to show that the physicists have no idea where they're going, and of TWP to show that they systematically misspend funds allocated to them?

 

[marcus]

... What do you suppose next year's will be like when congesspersons can wave around copies of NEW to show that the physicists have no idea where they're going, and of TWP to show that they systematically misspend funds allocated to them?

My advice to the top faculty at the top places is to diversify QG research DAMN fast.

Get rid of the monopoly WalMart look in fundamental research.

they should already have done a 10-20 percent diversification into non-string fundamental physics theory.

To my mind the ONLY seriously damning bit of evidence is that in the whole US there is only a single non-string research GROUP (with more than one faculty member)
And you can compare that with half a dozen non-string groups abroad.

And you still hear string apologists saying "we are the one best hope", "we are the only game in town", "our competition does not contact Newtonian gravity" (but see Rovelli's latest), "our competition does not contact QFT" ( but see Freidel)

If they would stop SOUNDING like they want a monopoly. And if they would act quickly to provide diverse QG options at the top departments, then they could legitmately reply Look, we are doing the best we can!.

It is that statement which does not ring true under the present circumstances.

 

[selfAdjoint]

I will quit this topic after this post. Marcus your response confirms my thoughts. I have often heard the same intransigence in political contexts; "The disasters are not our fault; our foes should have changed their bad ways! We were in the right! It can't be our fault!".

Many many years ago I read an essay by Hannah Arendt in the New Yorker. It was titled Fiat justitia et ruat respublica. "Do justice though the republic fall" (the original quote has heavens not republic but she changed it deliberately). She concluded that entailing the fall of the republic was a sufficient reason to shrink from pure justice. She was working on her book about revolution then, and perhaps she was thinking of Saint-Just and Robespierre. I was young and hasty at that time and I scorned her thought, but - "Oh, 'tis true, 'tis true!"

 

[Kea]

"Oh, 'tis true, 'tis true!"

Thank you, selfAdjoint, for some much needed counter levity. How ironic that M-theory should begin to become clear exactly now, amongst such a nauseating outburst of revolutionary rejoicing.

 

[selfAdjoint]

that M-theory should begin to become clear exactly now

Kea could you maybe start a thread laying out how you see M-theory in the light of modern n-categories or any other innovations you think may have a bearing? Are there any papers on the arxiv about it? Rather than bemoaning the trends perhaps we can start a valid counter-meme?

Not to be misunderstood; LQG and quantum gravity initiatives as we have seen them explicated here are a wonderful enterprise in physics and I hope and believe the eventual upshot will confirm the work of Thiemann, Rovelli, and all the others. But the insights from the other side are not chopped liver either! Nobody is anywhere near proclaiming victory in the unification stuggle, a struggle, I remind you all, against Einstein's "Old One" the keeper of nature's secrets, not against each other.

 

[CarlB]

Also, Kea, eventually I'd like a thread where you explain M-theory in blue-collar worker terms. But not until after I've had a chance to read Smolin and Woit's new books.

Carl

 

[ZapperZ]

Speaking of Woit, read his short interview in Physics World.

http://physicsweb.org/articles/review/19/9/3/1

As I've said many times before, eventually they'll discover superconductivity, and Carver Mead's assertion that it is the system that has the clearest manifestation of some of the most fundamental aspect of our universe at the macroscopic scale.

Zz.

 

[pelastration]

Speaking of Woit, read his short interview in Physics World.

http://physicsweb.org/articles/review/19/9/3/1

As I've said many times before, eventually they'll discover superconductivity, and Carver Mead's assertion that it is the system that has the clearest manifestation of some of the most fundamental aspect of our universe at the macroscopic scale.

Zz.

Yes superconductivity is very interesting.

Some materials have superconductivity properties, even ballistic conductivity. http://en.wikipedia.org/wiki/Ballistic_conduction" . Electrodes or wires can be deposited with graphene (sp2) or combined with sp3 (industrial diamond, glassy carbon). sp2 and sp3 combined can make together fullerenes.
Graphene has some strange properties, like if the electrons follow the mono-layer lattice it's ballistic conductive but if two separate layers are on top of each other they are completely insulated from each other.
Applications can be i.e. switches for electronics.

 

[marcus]

Since this is a thread about Smolin's book---and peoples views and reviews of it---I'd like to know if anyone has an idea of why the book has become a runaway best seller.

for two weeks, when I pull up the amazon general physics list it is always #1

and at the present its overall amazon sales rank is 256 compared with the #2 book which has rank 1235.

what this means is that in this case #1 is not just a little bit out ahead of #2 but it is WAY out ahead. (by a factor of 5 in storewide sales rank)

The books it is way out ahead of in sales are books by Greene and Hawking and Penrose and Randall and Susskind and Kaku. with some of them it is considerably MORE than a factor of 5.

So it's probably appropriate to wonder what if anything is different.

WHAT if anything MAKES THE SMOLIN BOOK SPECIAL?

I think it is because he doesn't just say that string has failed and hit the wall-----he discusses what comes NEXT. The word NEXT is in the title. He discusses a lot about what comes after.

I'm curious to know if anybody else who has read all or some of the book has a different take and has found some other angle of why the book is doing well in the market.

 

[CarlB]

WHAT if anything MAKES THE SMOLIN BOOK SPECIAL?

I think it is because he doesn't just say that string has failed and hit the wall-----he discusses what comes NEXT. The word NEXT is in the title. He discusses a lot about what comes after.

I'm curious to know if anybody else who has read all or some of the book has a different take and has found some other angle of why the book is doing well in the market.

Well string theory is in trouble and that makes for an audience, but what is truly remarkable about the book is that he tells the story in terms that a non technical audience can understand but without much of the talking down to that you might have seen in recent string theory books.

I think the book has got real legs. I bought a copy, no, I'm not lending it out. I wrote all over it. And I've influenced at least one person to buy a copy.

As I've said many times before, eventually they'll discover superconductivity, and Carver Mead's assertion that it is the system that has the clearest manifestation of some of the most fundamental aspect of our universe at the macroscopic scale.

Asking a solid state guy whether solid state has the answers to elementary particles is sort of like asking a librarian if books will help your sex life.

Carl

 

[ZapperZ]

Asking a solid state guy whether solid state has the answers to elementary particles is sort of like asking a librarian if books will help your sex life.

Carl

What does that have anything to do with Woit wanting to know more about superconductivity?

And considering that you are confused as to what "solid state physics" is versus "condensed matter physics" , I'd say that it is you who have been getting your info from librarians.

Zz.

 

[CarlB]

What does that have anything to do with Woit wanting to know more about superconductivity?

I was quoting you. You're the one saying superconductivity is the "clearest manifestation of some of the most fundamental aspect of our universe". Woit says nothing of the sort, either in his interview or in his book, though "Not Even Wrong" mentions suprconductivity in the usual explanation of the Higgs mechanism. Nor does Lee Smolin's book "The Trouble With Physics" mention anything about superconductivity as being a clue to getting physics out of trouble.

And considering that you are confused as to what "solid state physics" is versus "condensed matter physics" , I'd say that it is you who have been getting your info from librarians.

Your assistance is very much appreciated in correcting my terminology. But what are you doing over here in "Beyond the Standard Model?" I thought your attitude was that there is no experimental evidence against either QFT or SR/GR. I'm reminded of rule #3 in the "golden rules of plumbing":

(1) [Sewer lines are built with a slight slope because] "Feces flow down hill."

(2) "When you're splashing around in sewage, try to keep your mouth shut even if you have to breathe through your nose."

(3) "If it ain't broke, don't fix it."

(4) "Avoid biting your nails."

Carl

 

[marcus]

Asking a solid state guy whether solid state has the answers to elementary particles is sort of like asking a librarian if books will help your sex life.

:rofl:
Well they do help, don't they? I mean if you get the right kind of book.

So maybe librarians are right after all.

... what is truly remarkable about the book is that he tells the story in terms that a non technical audience can understand but without much of the talking down to that you might have seen in recent string theory books.

I think the book has got real legs. I bought a copy, no, I'm not lending it out. I wrote all over it. And I've influenced at least one person to buy a copy.

I think so to. I've been reading it and re-reading parts, for several days. I'm glad you liked it too. It's a great book.

 

[ZapperZ]

I was quoting you. You're the one saying superconductivity is the "clearest manifestation of some of the most fundamental aspect of our universe". Woit says nothing of the sort, either in his interview or in his book, though "Not Even Wrong" mentions suprconductivity in the usual explanation of the Higgs mechanism. Nor does Lee Smolin's book "The Trouble With Physics" mention anything about superconductivity as being a clue to getting physics out of trouble.

I never claim that Woit said such a thing. My claim that superconductivity has that property is well-known, and what Carver Mead also claimed in his PNAS article. No one, not even Steven Weinberg, challenged this even when Phil Anderson and Bob Laughlin made such statements in their essays on emergent phenomena.

Your assistance is very much appreciated in correcting my terminology. But what are you doing over here in "Beyond the Standard Model?"

Because (i) I am the moderator of this forum (ii) while I am an ardent critique of HOW lack-of-experimental-evidence area of physics is PRACTICED, I still see value in it. Unlike you, I do not denigrate whole areas of physics the way you look down on condensed matter/"squalid" state physics. I may object to how it is practiced, but this is way different than making derogatory slam towards an area of physics.

I thought your attitude was that there is no experimental evidence against either QFT or SR/GR. I'm reminded of rule #3 in the "golden rules of plumbing":

What does that have anything to do with anything? When asked to cite experimental evidence for whatever it is that you claimed - such as solid state mechanism are always known (quantum critical point?) or such system using QFT breaks down at "high energies" - you offered none.

I could also play your game and claim that your attitude seems to be dismissing empirical evidence as being anything significant that one should be concerned with. This is what Sheldon Glashow has criticized the String Theory community when he left Harvard for Boston University, and what John Rigden's pointed out as a major problem in physics in his pointed article in Physics today.

Zz.

 

[CarlB]

Unlike you, I do not denigrate whole areas of physics the way you look down on condensed matter/"squalid" state physics.

Gosh, I should have put a smiley face on it. I had read the term in either Woit's or Smolin's books and thought it was cute.

What does that have anything to do with anything? When asked to cite experimental evidence for whatever it is that you claimed - such as solid state mechanism are always known (quantum critical point?) or such system using QFT breaks down at "high energies" - you offered none.

I don't have time (or possibly the ability) to explain these things more fully to you. But I produced a link to a peer reviewed article where a non Lorentz invariant theory produced an "accidental" Lorentz invariance at low energies (just like I had claimed was possible) so if you want to deny that these things exist you are welcome to write a resonse to them (and publish it in the peer reviewed literature). And, by the way, they called it an "emergent", which I guess you like. As far as I can tell, "emergent" means that the little things don't necessarily have to be the same as the big things, which was exactly my point.

I could also play your game and claim that your attitude seems to be dismissing empirical evidence as being anything significant that one should be concerned with. This is what Sheldon Glashow has criticized the String Theory community when he left Harvard for Boston University, and what John Rigden's pointed out as a major problem in physics in his pointed article in Physics today.

You've left too much unsaid and I can't tell what you mean here. For instance, I'm too stupid to know what my game is. I haven't seen Rigden's article, can you provide a link? By "Physics today" do you mean "Physics Today" or "Physics, today"? Is there a "Physics" magazine? And I haven't read Glashow's complaint about string theory though I've seen a lot of short quotes of his.

My primary complaint about string theory is probably different from Glashow's or Rigden's. I think physics should rest on very simple principles and that string theory is too complicated.

Carl

 

[ZapperZ]

I don't have time (or possibly the ability) to explain these things more fully to you. But I produced a link to a peer reviewed article where a non Lorentz invariant theory produced an "accidental" Lorentz invariance at low energies (just like I had claimed was possible) so if you want to deny that these things exist you are welcome to write a resonse to them (and publish it in the peer reviewed literature). And, by the way, they called it an "emergent", which I guess you like. As far as I can tell, "emergent" means that the little things don't necessarily have to be the same as the big things, which was exactly my point.

Then you don't have any idea what "emergent" property means, because if you do, then you would have never made the claim that QFT is perfectly valid for condensed matter, but it isn't for the high energy scale. One only needs to look at the various articles and book that Bob Laughlin wrote to know that he claims that ALL of the behavior of the universe that we observe are essentially "emergent" phenomena, everything from the fractional charges of quarks to the so-called elementary particles, with identical to the description found in condensed matter. S.C. Zhang of Stanford, who was a high energy physicist by training, practically said the same thing now that he has gone into condensed matter and realize how relevant it is outside the boundary of its field.

And in case we are arguing between apples and oranges, the emergent phenomena here isn't about the METHODOLOGY or the TOOLS, such as QFT. You can use QFT for one particle, 2, particles, 12, particles, or all the way to many-body systems. What is "emergent" is the collective phenomena that appear at the many-body scale and not at the few body scale. You don't turn off one set of tools just because you now have an emergent property. Emergent behavior isn't about the tools.

And I made a mistake. It was Michael Riordan, not Rigden, in Physics Today.

http://www.physicstoday.org/vol-56/iss-8/p50.html

Zz.

 

[marcus]

Hi Carl and Zapper, thanks for adding so much to this thread!

The topic is the new book TwP by Lee Smolin and the topic of EMERGENCE, emergent properties and phenomena are important ones in the book.

first i will copy the index entries from Smolin's book. as I'll discuss, this doent begin to indicate how central the concept is to the whole book---it is is implicit in the discussion of background independent approaches to quantum gravity----where macroscopic properties of space and spacetime continua emerge from discrete combinatorial degrees of freedom.

So the idea of emergence infuses the whole section III "Beyond String Theory" where he discusses some of the newer non-string models of space time and matter.

So these few index entries don't adequately reflect how important the concept becomes later in the book (after page 200). But anyway I'll quote some abbridged ("snipped") exerpts from the index:
--quote TwP pp 378-379--
emergence [arising of new properties] 131-132

emergent particle 132

emergent properties 132...142

emergent string 132...141...

fundamental string [vs emergent string] 132-133
--endquote--

I don't have time right at the moment to go into how, in some versions of non-string QG, space and time are EMERGENT from more basic combinatorial degrees of freedom.

A crystal clear example of this is in the work of Renate Loll, where even the dimensionality of space is emergent----it is a macroscopic observable and can vary dynamically. Who's to say if this is good or bad, it is just how it is in that particular model

In background independent QG, emergence can be talked about EITHER as something that happens as you go from the FEW TO THE MANY
or as you go from the SMALL TO THE LARGE

So in that sense both what Carl said and what Zapper said about emergence agree. That is because the microscopic building blox of spacetime (and latterly matter is trying to be included too) are Plancksize. so FEW = SMALL, and many = macroscopic.

I hope in this thread we can just use Smolin's definition of emergence---since the thread focus is his book and that we don't have to debate the meaning of the word which will necessarily vary from writer to writer

I will get back to this interesting discussion later

 

[Kea]

As I've said many times before, eventually they'll discover superconductivity, and Carver Mead's assertion that it is the system that has the clearest manifestation of some of the most fundamental aspect of our universe at the macroscopic scale.

Hi ZapperZ

I can't say that I've read the books, or any of the interviews, but personally I agree that superconductivity is an important system. Actually, I worked in highTc experiment back in the mid80s - an exciting time. A few years after that everyone was saying that Quantum Groups would be able to explain superconductivity. I gave seminars on the subject, but all my colleagues said that something that abstract couldn't possibly be useful for physics. Then in the mid90s I got hooked on categories. By now, all my colleagues were into Quantum Groups, but they said that something as abstract as Categories couldn't possibly be useful for physics. Now...

Unfortunately, I can't claim to have kept up on developments in superconductivity. I have been to some interesting seminars on the topological phases for highTc, and find it very exciting that the phase diagram is being cleared up. Of course, theoretically things are NOT yet clear, but I have no doubt whatsoever that a working M-theory should have something to say about emergent phenomena. The nice feature of our approach to M-theory is that 'constraints' on the theory are dictated entirely by the experimental question. This means that different systems are equally fundamental, whether it's superconductors, or classical cosmology, or QFT.

 

[CarlB]

ZapperZ, thanks for the link to the Riordan paper:

http://www.physicstoday.org/vol-56/iss-8/p50.html

I very much agree with everything in this article. Everyone working "beyond the standard model" has their own version of what in the standard model should be kept, and what should be discarded, and this variety of opinion is a healthy thing. With that said, some passages that I most heartedly agree with are:

Except for a few stalwarts, theorists were abandoning field theories and constituent models of the strong force.

I think that this is also the problem with the present time. I believe that the way to "beyond the standard model" is through field theory and constituent models.

But how can we ever hope to make meaningful measurements at this scale when we have such difficulty building particle colliders to work at the comparatively lowly Higgs scale?

I feel that constituent models will be able to get past this problem in that they must allow calculation of standard model parameters. This is why I take notice of things like the Koide mass formula. Any coincidence that is not explained within the standard model could possibly be a clue to a more fundamental theory.

One of the great strengths of scientific practice is what can be called the "withering skepticism" that is usually applied to theoretical ideas, especially in physics. We subject hypotheses to observational tests and reject those that fail. It is a complicated process, with many ambiguities that arise because theory is almost always used to interpret measurements. Philosophers of science say that measurements are "theory laden," and they are.

I especially agree with this in regard to the "ambiguities". This gets back to the question of why it is that none of the thousands of BRILLIANT physicists who have been working on the problem for most of the last 100 years have not unified SR/GR and QM. My opinion is that our understanding of space and time has to be modified so as to make both these theories natural and naturally fit together. Unfortunately, that means breaking a few eggs to make an omelet. But the ambiguities that Riordan refers to makes it possible to break those eggs without losing their excellent history of experimental predictions.

What I don't like about string theory is the apparent absence of a path from the theory to a derivation of the details of the standard model. The standard model is a fairly complicated thing, and it is understandable that no 30 page paper is going to give a derivation of it from deeper "first" principles. I don't see anything less than a 150 page book deriving the standard model. The string theorists have had more than long enough to write that book and they have failed.

For the same reason, I don't think that it is possible for anyone to say with certainty that some rather speculative path cannot possibly lead to a deeper theory until that path has been fully explored. The experimental evidence is fraught with ambiguity. Thousands of physicists have explored various small changes to the standard model and have failed to extend it beyond where it is today. I think that this is good evidence that larger changes need to be countenanced than those that the brilliant physicists, who have been working on this for so long, have been willing to face.

Carl

 

[Kea]

http://www.physicstoday.org/vol-56/iss-8/p50.html

Wow! The guy admires Peirce, one of the founders of category theory:

He was popularizing the views of his idiosyncratic colleague Charles Sanders Peirce, one of the few philosophers of science with experience doing experiments.

 

[Kea]

I don't see anything less than a 150 page book deriving the standard model.

I disagree. This is where the fancy maths really does mean something. The simple geometry of Baratin-Friedel can be described in about 30 pages, and a translation into category theory can be made even shorter.

 

[ZapperZ]

Hi ZapperZ

I can't say that I've read the books, or any of the interviews, but personally I agree that superconductivity is an important system. Actually, I worked in highTc experiment back in the mid80s - an exciting time. A few years after that everyone was saying that Quantum Groups would be able to explain superconductivity. I gave seminars on the subject, but all my colleagues said that something that abstract couldn't possibly be useful for physics. Then in the mid90s I got hooked on categories. By now, all my colleagues were into Quantum Groups, but they said that something as abstract as Categories couldn't possibly be useful for physics. Now...

Unfortunately, I can't claim to have kept up on developments in superconductivity. I have been to some interesting seminars on the topological phases for highTc, and find it very exciting that the phase diagram is being cleared up. Of course, theoretically things are NOT yet clear, but I have no doubt whatsoever that a working M-theory should have something to say about emergent phenomena. The nice feature of our approach to M-theory is that 'constraints' on the theory are dictated entirely by the experimental question. This means that different systems are equally fundamental, whether it's superconductors, or classical cosmology, or QFT.

Hello Kea.

It appears that our paths have some similarities. My Ph.D research was on high-Tc superconductors, specifically on tunneling spectroscopies of high-Tc superconductors (Yes, I admit it, I'm an experimentalist in a sub-forum that has barely any experimental appreciation). Furthermore, I did my postdoc on photoemission spectroscopy of high-Tc superconductors. So for the longest time, I was heavily involved in this field when I decided to get out and go into accelerator physics where my condensed matter background is actually needed in the design of a high quantum efficiency photocathode in an RF injector. So like you, I left the field for something less ... how shall I put it, ... taxing.

However, I still keep up with the field and continue to referee papers related to my earlier work. Having crossed to other fields, I realize that most people outside of condensed matter are almost totally ignorant of the importance of that field. They still think it is nothing more than "engineering", that it is simply an application of physics to make stuff. Of course, they just gasp (especially the young graduate students and postdocs) when I tell them that the Higgs model, for example, came right out of condensed matter physics.

I think that what people simply don't realize is that we gain insight into certain problems from sources we just don't anticipate. Peter Higgs found it in, of all places, a condensed matter magnetic system. A superconductor is, to me (and apparently to Mead also), the clearest indication of quantum phenomena at the macroscopic scale. It is why we see some of the most fundamental test of QM, such as the Schrodinger Cat-type states, being done using such system. I fully expect that the definitive evidence for other issues surrounding QM such as Bell-type results, will come from such system as well.

Zz.

 

[Kea]

Hi ZapperZ

It appears that our paths have some similarities. My Ph.D research was on high-Tc superconductors, specifically on tunneling spectroscopies of high-Tc superconductors.

Unfortunately, I was still a teenager when I started working in Prof Taylor's lab, so although I did quite a bit of work I never got to a PhD in it. We were making brand new YBaCuO type ceramics (from scratch with the mortar and pestle, building the lab up, figuring out which thermocouples worked best and all that) and checking out any properties we could because it hadn't been done! I also ended up doing an honours project in mechanical properties later on, but then I moved into a biomedical engineering laboratory. I agree that Theoretical Physics is sorely lacking in experimental insight these days. They even call it mathematical physics, as if that is somehow more sophisticated and relevant. I always tell everyone that I'm a Theoretical Physicist.

However, I still keep up with the field and continue to referee papers related to my earlier work.

You know, I would really appreciate it if you started a short thread here (since we are talking Beyond the SM) listing some up-to-date references that we could read to get a handle on current thinking. I regret not having kept up with it, but I actually left physics all together for quite some time and never thought I would come back to it.

Having crossed to other fields, I realize that most people outside of condensed matter are almost totally ignorant of the importance of that field.

Yes, I have observed this. When I mentioned CMP in the context of M-theory at a recent String theory conference, I was met with a number of confused frowns.

The mathematically sophisticated but physically minded Microsoft people have thought a bit about this. See for example Freedman et al. in
http://arxiv.org/abs/cond-mat/0307511