The Trouble With Physics

[exile]

The Trouble with Physics: the Rise of String Theory, the Fall of a Science, and What Comes Next, by Lee Smolin, a leading particle physicist and proponent of an increasingly favored alternative approach to the unification of gravity and quantum field theory. Basically, his book is a second indictment, along with Peter Woit's Not Even Wrong, of string theory's lack of predictive content, and the sociological distortions in the field which basically entail that young physicists, in order to have any chance of success, have to sign up to work in a theory which posits at least 10^(500)—that's right, a google raised to the fifth power—of distinct vacuum states (each corresponding to a distinct way the universe could be), with no possible way to sort amongst them, and where, moreover, even the most ardent defenders of the 'theory' admit that they cannot really say what its content is, or how it could possibly be tested (in crashing contrast with the Standard Model of quantum field theory). Since my own field of syntactic theory is in exactly the same condition (even unto a kind of parallel between Noam Chomsky and Ed Witten, except that EW appears to be vasly more intellectually honest than NC), and since physics was my major until I switched late to linguistics, I'm really fascinated and way, way dismayed to read that the toxic conditions in my own field are so closely paralleled in what I've always regarded as the paradigm of scienctific method and success...

 

[arnisador]

Those two books prompted a lot of discussion here (based on their reviews--no one read them) about whether a generation of physicists was indeed being wasted on a search for a way to turn lead into gold as it were. People have strong opinions. As a mathematician I appreciate its beauty and mathematical depth, but as a scientist I am suspicious for the reasons stated.

Trouble in linguistics? I know classics has had some real problems (and enjoyed Who Killed Homer?).

Noam Chomsky

My political scientist father-in-law used to claim he substitute-taught for him when he was off politicking, but I never believed him.

 

[exile]

Those two books prompted a lot of discussion here (based on their reviews--no one read them) about whether a generation of physicists was indeed being wasted on a search for a way to turn lead into gold as it were. People have strong opinions. As a mathematician I appreciate its beauty and mathematical depth, but as a scientist I am suspicious for the reasons stated.

Woit's book is very challenging, based as it is on the use of Lie symmetry groups and Weyl-style representation theory (this seems to be similar to model theory in the interpretation of various logics) in quantum field theories, and fairly technical discussions of guage symmetries in the electroweak/QCM unification. Woit uses little explicit mathematics, but it might be better if he had done, because his prose is extremely dense and presupposes the results of the fairly dense mathematics of symmetry-group theory and QFT without actually showing you how those results were obtained. In my own education I reached the point where, with the help of various fairly user-friendly textbooks, I was able to follow the solution to the Dirac equation and understand how spinor representions gave rise to alternative solutions corresponding to electrons and positrons respectively; but Woit sort of starts from the assumption that you know what the Dirac equation is all about and why it was so innovative and takes off from there in a very steep curve. It's like a black diamond run on a very difficult ski hill... still, the technical detail carries a good deal of conviction and plausibility to Woit's claims. (He himself hates the Calabi-Yau topological representations for the compactified string-space dimensions, mostly, I gather, for a physicist's reasons—they are so underdetermined and vast in number as to basically allow you to say anything you like, with no way to reduce them to even a finite number of candidates, apparently—one of the nasty shocks that string theorists got as they emerged from the early heady days, apparently...) Smolin's book is more leisurely and roundabout, and its corners are a good deal less sharp, if I can put it like that... I'm still in the first quarter of the book, but it's clearly a good one, and I think the two of them are going to put a lot of pressure on the string-theoretic community. Probably a lot of people have been thinking that grand unification was just around the corner, and now the whistle has been blown on that fantasy... I really wish it were otherwise. I'd like to see that in my own lifetime, and the clock ticketh on...

Trouble in linguistics? I know classics has had some real problems (and enjoyed Who Killed Homer?).

The two situations, in physics and syntax, are actually very similar, scarily so. The current avatar of MIT syntax, minimalism, isn't even referred to as a theory; Chomsky calls it a 'program' and it has so many trapdoors and fire-escapes and 'free parameters' that basically, nothing follows from anything (sound familiar? ); and at the same time, if you're a graduate student in syntax, there are maybe five major research departments in the US where you can reasonably contemplate a job opening up that you'd be eligible for—us, Stanford, UT at Austin, Chicago, maybe Michigan (if they ever decided to hire a theoretical syntactician, and it's not really a major department, come to think of it) and one or two others. All the rest of the departments in the US are secondary or tertiary branch plants of MIT, or are trying to be...

My political scientist father-in-law used to claim he substitute-taught for him when he was off politicking, but I never believed him.

Naah, doesn't sound like the ring of truth to me....

 

[Sukerkin]

I popped in to see what people were reading and all of a sudden my brain melted .

I sense the possibility of a serious side-thread from the above few posts as I too have a feeling that the bleeding-edge of physics is adopting an all too familiar 'religious' tone wherein 'faith' is expected before you may study and advance.

 

[exile]

I popped in to see what people were reading and all of a sudden my brain melted .

I sense the possibility of a serious side-thread from the above few posts as I too have a feeling that the bleeding-edge of physics is adopting an all too familiar 'religious' tone wherein 'faith' is expected before you may study and advance.

The problem is not unlike that of religious faith, in a way—at least, that's how it looks to me—but with a subtle difference. Faith, in the ordinary sense, anyway, seems to require that you accept a certain view of the universe, one in which it is pervaded with something like an overarching, infinite intelligence, or projection of something related to what we recognize in human personality or identity, or consciousness. The issue in physics doesn't seem to have that characteristic; rather, you have to accept that certain characteristics of an explanation trump others (conceptual economy, in a certain specific sense, trumps the requirement that the framework make testable predictions (whether or not these match well with observed data); mathematical beauty and tractability in certain domains trumps the need for a comprehensive and complete specification of what the theory itself consists of, and so on). Faith in both cases, in a way, but the crucial difference is that religious faith involves ontological commitments—commitments to the existence of some being, some entity of some kind—that are primary. The kind of faith involved in, say, string theory, is that while the outcome of your theory may commit you to the acceptance of certain entities (such as existing alternative universes), these aren't primary commitments; if it turned out that you could have your theory, but in a more refined form which eliminated the need for alternative universes, you'd happily give them up. What you're committed to isn't ontological, but methodological: a set of preferences about what properties your theory should have. The commitment isn't to something about the universe, but to something about the theory which explains the universe.

In the case of string theory, the primary commitment is probably to the possibility of unifying gravitation and quantum field theory, and therefore the behavior of gravity on the one hand with the behavior of the electromagnetic, weak, and strong nuclear forces, using a model in which 'strings' vibrating in a way which corresponds to an extremely complex topological manifold called a Calabi-Yau space—a model which, in the ideal limit, yields the behavior of all known particles (and the fields that affect them, or which they represent the carriers of) as well as gravitation. The problem is that in accepting the primacy of this aspect of your physical theory, you give up the possibility of predicting the properties of the universe, because there turn out to be at least a google to the fifth power ways to configure the vacuum state (and hence the rest of the universe) to conform with what is known about the theory at this point. And there doesn't seem to be any promising direction to go in which will reduce the class of possible universes admitted by the theory to a single one—one which happens to have exactly the properties of the one we live in.

The way the string theorists get around this nasty little problem is called the anthropic principle: the idea that we happen to live in a universe which has just the properties necessary to support live and the emergence of intelligence. This seems to be a truism, and it is—until you combine it with the problem of figuring out what to do with all those 10^(500) possible universes: if string theory (when we finally get it in explicit form) is a complete account of nature, then string theory, which entails that 10^(500) universes could exist, further entails (because it is a complete theory, and tells us everything that can ever be told by a physical theory) that these universes do exist (because if they didn't, the reasons why some of them did and some didn't wouldn't be part of the theory, which would contradict the initial assumption that string theory is a complete theory of nature. So they must exist). In which case, the fact that our universe has the properties it has—that the constants of nature, and other 'free parameters', have the values they do—isn't built into the theory; in principle, the theory admits not a single value for each of these constants, but a range of values, each of which must be true in some universe if the theory is correct. As it happens, we do not see these other universes because there is no way for them to interact. But they exist, and some of them have conditions to support life, in some form or other, and some don't, and clearly life will only evolve in universes which meet the conditions that are required to support life. We just happen to live in one of those, that's all. In other words, the anthropic principle gives us an alibi for why we happen to live in the kind of universe we do: it just happens to be one of the google to the fifth power of possibilities which supports life. There's nothing unique about it, and nothing which requires special explanation.

Obviously, the problem with this theory is that it has completely given up trying to account for the properties of the vacuum state, aka fixing the values of the free parameters of the theory, in the universe we actually observe, the only universe that we have data about, the only one that can confront the theory with facts which could affect our view of its predictive success. Quantum field theory in contrast has always had as its goal the creation of a field theory in which the values of the constants of nature in the one existing universe we can observe (and which, as the null hypothesis, is the only one we have justification for believing exists) were theorems of the field equations (which, ideally, would contain no free parameters themselves), with all forces manifestations of a single Ür-force, broken up into the four known (plus maybe one semi-known) forces by spontaneous symmetry breaking in the early universe. In lieu of such a theory, string theory gives up the idea that there is a single universe, and becomes, rather, a theory of the form of alternative universes, which—apart from the one we live in—we can never observe. Its empirical content is therefore, essentially, nil, and it has become, in the view of quantum field theorists, an exercise in sterile mathematical proofs. But it's crucial to recognize that the faith involved isn't really faith in the normal, ontological sense, but rather an essential æsthetic faith about what aspects of a theory of nature are to be given primacy...

 

[arnisador]

II sense the possibility of a serious side-thread from the above few posts

I appreciated and enjoyed exile's detailed posts but taking the hint, perhaps rather than replying to them here I'll ask if some mod. could move these few posts to The Study?

 

[exile]

I appreciated and enjoyed exile's detailed posts but taking the hint, perhaps rather than replying to them here I'll ask if some mod. could move these few posts to The Study?

Well, I'm involved in the thread and therefore durst not! But I think that the last few posts would make an interesting platform for further discussion... will see what can be done...

 

[Sukerkin]

Good retort to the suppostion that physics is becoming more like a religion, Exile :tup:. I think I may print out post#5 for re-reading as the theory thumbnails are pretty good.

It does seem to me, as an interested layman, that mathematical elegance is starting to overtake predictive content as a primary yardstick for the worth of a new theory. My query lies in the old saw that if a theory admits to no way for it to be tested and disproven then, as far as my primitive (Popperian ) scientific knowledge goes, that's not science.

Perhaps it is simply the fact that my knowledge of the background mathematics isn't deep enough?

I don't really understand how something being a theoretical mathematical construct based upon certain un-testable assumptions is different in character from a group of theologians debating how many angels can dance on the head of a pin. If some of the foundations are taken as read (on 'faith' if I may call it that) then the whole model inherits that 'flaw' of lack-of-disproveability.

If those assumptions (or the model that derives from them) are testable for predictive capability then the 'faith' element goes away, otherwise the fascinating theories of the nature of the universe are mathematical poetry.

I'm not being deliberately obtuse here by the way, I really am that stupid { } in that picking and chosing what assumptions you like to make the maths work out sounds dangerous close to the kind of pseudo-science jiggery-pokery we get up to in economics :lol: .

 

[Lisa]

I think a warning should be placed on this thread:

"WARNING: DO NOT OPEN UNLESS YOU HAVE HAD SUFFICIENT AMOUNTS OF COFFEE OTHERWISE YOUR BRAIN MIGHT GO INTO SEIZURES"



All joking aside. Interesting discussion fellows. Sorry I have nothing to add. I will read it more in depth after my second or third cup.

 

[exile]

Good retort to the suppostion that physics is becoming more like a religion, Exile :tup:. I think I may print out post#5 for re-reading as the theory thumbnails are pretty good.

It does seem to me, as an interested layman, that mathematical elegance is starting to overtake predictive content as a primary yardstick for the worth of a new theory. My query lies in the old saw that if a theory admits to no way for it to be tested and disproven then, as far as my primitive (Popperian ) scientific knowledge goes, that's not science.

That's the primary point of both books. And what's interesting is that the point is not disputed even by ardent string theorists; their response instead is to make snide comments about the relevance of the Popperian yardstick (in his book, Woit cites a contemptuous remark posted on some string-theory website or other about the 'knee-jerk Popperazi', a clever way of expressing what I think of is the abandonment of the basic scientific touchstone: knowing in explicit detail what your hypothesis commits you to and being prepared to abandon that hypothesis if you keep coming up empty). He points out that the string theorists have yet to specify just what their answer to the question If this were wrong, how would we know? would be—what would have to happen in order for them to be willing to give it up.

Perhaps it is simply the fact that my knowledge of the background mathematics isn't deep enough?

No. That's not it. The mathematics involved are novel and frighteningly difficult (way more difficult, if I understand what I've read, than the differential tensor geometry that Einstein appropriated from a couple of late-19th century Italian mathematicians as the geometric language which he needed for general relativity, though at the time that was regarded as being at the limits of comprehensibilty, at least so far as working physicists were concerned... how things change, eh?) Arni can tell you a lot more about it, I'll bet, if you've got the nerve. But that's not the problem. The problem is attitude: what you are willing to give up in order to get what you want. We have exactly the same problem in syntactic theory, so I feel Woit's and Smolin's pain, and that of the other dissenters (of whom there seem to be quite a few). The problem seems to be that a lot of physicists see no other way to link quantum field theory to gravitation, and the hope that string theory holds out of a successful unification—and that's all it is at the moment, a hope—has created in the mnds of many of the string theorists the following (and IMO deadly) premise:

String theory is too good to be false.

As Smolin points out, beautiful premises in the hard sciences often fail the test of confrontation with the data, and are discarded in normal scientific practice. What's happening in string theory is a frightening anomaly in science precisely because, when the strongest version of the theory is confronted with the facts and fails, string theorists do not go back to the drawing board. What they do is reject the relevance of the facts, in effect, in a way which changes the nature of the enterprise completely. Too many vacuum states? No way to reconcile the theory with the apparent value of the cosmological constant? No motivation for why the eleven dimensions of space you need are compactified in such a way that only four of them—the classic four of spacetime—are measurable? Simple. 'Generate' all the possibilities that the theory still allows—the infamous one followed by hundred zero, raised to the fifth power—and then haul in the anthropic principle so that you can say, 'well, they're all there, and we observe the values for the fundamental constants of nature that we do because those values belong the set of sets of possible values that correspond to the possibility of intelligent life. Now go away and don't bother me.' And if you say, well, isn't that a bit expensive, just to get the hope of unifying gravity with the other forces of nature, the answer will be, well no, because that's the only game in town that offers that hope. That, however, seems to be sheer propaganda—there are other approaches out there, but they aren't being developed very fast because if you want to get a job in physics, you better not be working on loop quantum gravity or one of the other alternatives. The people hiring are all string theorists, and they don't want to hear what you have to say...

I don't really understand how something being a theoretical mathematical construct based upon certain un-testable assumptions is different in character from a group of theologians debating how many angels can dance on the head of a pin. If some of the foundations are taken as read (on 'faith' if I may call it that) then the whole model inherits that 'flaw' of lack-of-disproveability.

If those assumptions (or the model that derives from them) are testable for predictive capability then the 'faith' element goes away, otherwise the fascinating theories of the nature of the universe are mathematical poetry.

Well, speaking of poetry, remember Keat's profoundly misleading conclusion to 'Ode on a Grecian Urn':

Beauty is truth, and truth beauty,
That is all ye know, and all ye need to know.​

As a guide to hypothesis formation, yes. But as the test of the hypotheses formed, no—and the history of science is full of warning about how big a false step adopting that position is. This is the problem: Homo sapiens, Linnaean taxonomic name notwithstanding, tends to be not very wise, even when it's being very smart...

I'm not being deliberately obtuse here by the way,

? You're not being obtuse at all, Mark, these guys in the trade are saying exactly the same thing!

I really am that stupid { } in that picking and chosing what assumptions you like to make the maths work out sounds dangerous close to the kind of pseudo-science jiggery-pokery we get up to in economics :lol: .

Or in my own field, or in many others as well. And it's particularly bad if it happens in physics, the hardest of the hard physical sciences, because economists and syntactitions and all the rest can say, well, if those guys do it, why are you knocking us for doing it?? When your gold standard starts showing signs of being iron pyrite, you're in a hell of a lot of trouble....

I think a warning should be placed on this thread:

"WARNING: DO NOT OPEN UNLESS YOU HAVE HAD SUFFICIENT AMOUNTS OF COFFEE OTHERWISE YOUR BRAIN MIGHT GO INTO SEIZURES"



All joking aside. Interesting discussion fellows. Sorry I have nothing to add. I will read it more in depth after my second or third cup.

The technical details are important, but the really important thing is that the points that Woit and Smolin make are not really disputed by string theorists; they just don't see it as relevant. Consider the following negative comment about string theory:

You don't know what you are talking about.... The state of physics today is like it was when we were mystified by radioactivity... They were missing something absolutely fundamental. You are missing perhaps something as profound as they were back then.​

.

Pretty damning, eh? Now change the 'you' here to 'we' in all cases, and you have the actual comments of David Gross, one of the most active and intense advocates of string theory, a Nobel Prize winner for work on quantum field theory, delivered at a meeting of a conference to 'celebrate the theory's progress', as Smolin (p. xv.) reports dryly. Gross is talking about his own work and his colleague's work... and this is not unusual to hear from string theorists! But they won't give it up, or even step back from it a bit and try to rethink the whole project. It's, well, too good to be false.... :uhohh:

 

[Lisa]

The technical details are important, but the really important thing is that the points that Woit and Smolin make are not really disputed by string theorists; they just don't see it as relevant. Consider the following negative comment about string theory:

You don't know what you are talking about.... The state of physics today is like it was when we were mystified by radioactivity... They were missing something absolutely fundamental. You are missing perhaps something as profound as they were back then.​

.

Pretty damning, eh? Now change the 'you' here to 'we' in all cases, and you have the actual comments of David Gross, one of the most active and intense advocates of string theory, a Nobel Prize winner for work on quantum field theory, delivered at a meeting of a conference to 'celebrate the theory's progress', as Smolin (p. xv.) reports dryly. Gross is talking about his own work and his colleague's work... and this is not unusual to hear from string theorists! But they won't give it up, or even step back from it a bit and try to rethink the whole project. It's, well, too good to be false.... :uhohh:

So basically, in a nut shell, and correct me if I am wrong. String theorists are spending time and energy and money on a hypothesis that they can never prove and at the same time brow beating all of those who believe that they are going down the wrong path?

 

[exile]

So basically, in a nut shell, and correct me if I am wrong. String theorists are spending time and energy and money on a hypothesis that they can never prove and at the same time brow beating all of those who believe that they are going down the wrong path?

You got it, Lisa.

The payoff (and not in a good sense) is going to come a couple of decades down the line, when the lack of alternative research (because people now who are pursuing alternatives aren't getting jobs, or postdocs, or research funding, due to the stacked-deck aspect of hiring committees, grant review panels and so on) will leave the field without any way to backtrack to different approaches that might actually prove predictively effective. The field seems to be killing itself by failing to encourage what has always been essential in science: simultaneous pursuit of multiple alternative lines of explanation. That's almost always how we've made progress in the past: a kind of adversarial model (in the legal sense), where people have argued both sides, or all three, or four sides, of a question till the majority of the onlooker finally decided where the most profitable line of future development lay. We don't have that situation now. If string theory continues to go nowhere, there just isn't enough demography supporting any alternatives for the field to actively develop these alternative lines. And the current harsh conditions for non-stringers will drive a number of those who do currently pursue alternatives out of the field, eventually...

This really gets to me because my own field, theoretical syntax, is in exactly the same situation, and has been for the better part of half a century. We may actually be a little better off than the physics community, but the sociology and economics are very, very similar....

What people like Woit and Smolin are calling for isn't abandoment of string theory; they just want some intellectual honesty from the string theorists about the grave foundational problems that 'theory' (it's not, by consensus on both sides of the argument, actually a real theory at this point!) faces. And they want the kind of monoclonal cultivation of physics that seems to become the norm to be replaced by the contending-schools-of-thought model where different view clash and bang against each other till the last one standing can legitimately claim the prize. But that's not what's happening, and the prospects are bleak for the situation they're describing ending any time soon.

 

[newGuy12]

Oh, I think that there are some Big Boys who are going to get some very hard results soon about some very interesting science soon enough Exile!

Don't worry, someone somewhere will think about experiments that can be run, it just takes some very brilliant people to think them up, how to set up the experiment!

*** Note that I am not qualified to be in this thread, but I post anyway *** We will see more and more good science, it will work out in the end!

 

[shesulsa]

Ugh! Brain hurt! Feel Blonde! More Coffee!

*This message brought to you by an underachieving stay-at-home mom with insufficient caffeine-to-intelligentsia ratios*

 

[Lisa]

I have faith in human nature and our ability to be curious. Sometimes we are faced with adversity but it only takes one man to step out of the norm, prove an accepted school of thought to be wrong and allow science and mankind to move forward and evolve. As much as these men are facing adversity, their curiosity and the curiosity of those after them will prevail.

 

[Big Don]

I popped in to see what people were reading and all of a sudden my brain melted .

Heh, I misread it as psychics about ten times...

 

[Steel Tiger]

a theoretical syntactician

For the life of me, there's a term I never thought I would hear.

The payoff (and not in a good sense) is going to come a couple of decades down the line, when the lack of alternative research (because people now who are pursuing alternatives aren't getting jobs, or postdocs, or research funding, due to the stacked-deck aspect of hiring committees, grant review panels and so on) will leave the field without any way to backtrack to different approaches that might actually prove predictively effective. The field seems to be killing itself by failing to encourage what has always been essential in science: simultaneous pursuit of multiple alternative lines of explanation.

But we've seen this before. When String Theory itself was just getting off the ground, its proponents were unable to get those positions because of Standard Model and particle theorists. Now it looks like we have the reverse. With luck, the higher minds will keep soldiering on and find something to make this work or to shut it down.


Now this isn't my field (not even close!), but I am fascinated by it (have been since I saw the documentary based on Brian Greene's work, The Elegant Universe) and I have a few questions.

Are smolin and Woit discussing just String Theory or are they including M-Theory as well?
How does all this sit with the various dimension theories for the universe (you know all that multiverse stuff), or has it just absorbed them?
How does it sit with the Penrose-Hawking Singularity Theorem?

I guess like most people who were paying any kind of attention to it, String Theory seemed like the next obvious step in the evolution of reconciling the various seemingly disparate forces of nature. Of course, it still seems that way, it just can't be tested in a good and proper way.

 

[elder999]

Well, as "somebody" stated here years ago :lol:, if it's unmeasurable, and untestable, it's not a theory. It's a "metaphysical wonderland."

 

[exile]

For the life of me, there's a term I never thought I would hear.

You don't want to know, ST... but basically it's what Noam Chomsky brought into the world, with a little mostly unacknowledged help, back in 1957. Theoretical syntax began as the application of what has became known as computation theory to the sets of sentences that natural languages comprise. It seeks to identify the opimal data structures that are involved in the 'wetware' encoding of the human capacity to form sentences, including our ability to link, in crucial ways, parts of sentences that can be arbitrarily distant from each other. Basically, if you had what theoretical syntacticians are looking for, you could encode English, or any other natural language, as a set of instructions in code that would allow a computer to pass Turing's test: a normal human speaker, interacting with the computer via a keyboard, would be unable to distinguish the interaction from an interaction with another normal human speaker and would consistently fail to identify the computer as his or her partner in the interaction better than random chance would dictate.

But we've seen this before. When String Theory itself was just getting off the ground, its proponents were unable to get those positions because of Standard Model and particle theorists. Now it looks like we have the reverse. With luck, the higher minds will keep soldiering on and find something to make this work or to shut it down.

That's where the sociological distortion that's already occurred is going to make things very rough for anyone to try to kick the addiction...

Now this isn't my field (not even close!), but I am fascinated by it (have been since I saw the documentary based on Brian Greene's work, The Elegant Universe) and I have a few questions.

Are smolin and Woit discussing just String Theory or are they including M-Theory as well?

M-theory as well. They identify M-theory, particularly 'brane cosmology', as the place where string theorists go when it turns out that they can't come up with a demonstrably consistent string theory that accounts for the findings of Standard quantum field theory without taking on horrors they don't want to. M-theory is even less explicit and predictive than string-theory...

How does all this sit with the various dimension theories for the universe (you know all that multiverse stuff), or has it just absorbed them?

Just absorbed them, I think. It's not clear to me what the relationship is between the string theory multiverse and the Everett multiple-worlds interpretation of QM is, and I've never seen that discussed. But Everett is not a touchstone name in string theory, so the answer is probably, no relationship at all.

How does it sit with the Penrose-Hawking Singularity Theorem?

That presumably would emerge from brane cosmology, if there ever turns out to be an actual theory to go along with the name. So far, I doubt very much that string/M-theory has anything to say, since contrary to the advertising, it only offers a schematic way to derive general relativity from the properties of Calabi-Yau descriptions of string vibrations. The P/H theorem assumes general relativity, and the curvature tensor formulation of GR; without a full string-theoretic construction of GR, it's very unlikely that you could get the P/H theorem directly from the Calabi-Yau (or the still more complex brane-topological) vibration-mode descriptions. I'll say this, though: Roger Penrose hates string theory as much as Woit does....

I guess like most people who were paying any kind of attention to it, String Theory seemed like the next obvious step in the evolution of reconciling the various seemingly disparate forces of nature. Of course, it still seems that way, it just can't be tested in a good and proper way.

There are alternate ways, such as the loop quantum gravity that Smolin works in, that are keeping their heads above water; but the whole field is skewed in a way that is going to cause a train wreck down the road if things persist the way they're going. I actually think quantum field theorists are partly to blame, though; string theory plays the monster to their Frankenstein, at least to some extent. The reconciliation of electricity and magnetism via certain purely formal adjustments to Maxwell's equations led to a phenomenal series of discoveries, giving the QFT people the idea that the way to the future was to try to generalize symmetry groups to include more and more of the forces of nature; yes, there were (luckily) empirical consequences within accessible energy ranges. But there might not have been, and yet the grand unification project linking QED with the weak force, and the electroweak synthesis with the QCD theory for the strong force, would have gone on anyway, because the quantum field theorists had gotten hooked on the idea that you make progress by extending the guage-theory formalism more and more widely. Getting at the fundamentals of nature became generalizing the mathematical formulation of the field laws. And that ethic is exactly where string theory got its initial momentum from, and its attractiveness. So you could say that the QFT people got the monster they deserved... but I don't think that that's quite fair either...

 

[Steel Tiger]

Now you've got me thinking. Most specifically about loop quantum gravity. If the theory might have difficulty quantizing gravity into 3+1 dimensions without creating matter and energy artifacts what does it do with antimatter?