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August 19, 2006

Not Even Wrong

Posted by Aaron

The physics blog-wars have hit the world of publishing with Peter Woit’s Not Even Wrong and Lee Smolin’s The Trouble with Physics. Having given up blogging long ago, I still seem to have spent an inordinate amount of time in these internet trenches. Since Dr. Woit was kind enough to send me a review copy of his book, once more into the breach I suppose. Here is my contribution to the chorus of reviews that will surely be appearing. Like the book, it is aimed at the general public rather than towards physicists.

Review of Not Even Wrong

Any comments and corrections are greatly appreciated. The first paragraph follows after the jump.

String theory, the enormously ambitious and speculative endeavor that has, for the past thirty years, attempted to unify our understanding of quantum mechanics and gravity has failed to live up to its initial promise. Its relative domination of the field of fundamental theoretical physics has long led to criticism within the scientific community. In the last few years, however, a number of popular books and television shows have made the case for string theory to the public. There is certainly a place, then, for these criticisms to also be presented to the public. More so, the sociology of modern theoretical physics could provide a fascinating context in which to present a reasonably disinterested discussion of the pros and cons of both string theory as a research program and the way in which modern theoretical physics is pursued. Dr. Woit has instead chosen to write a tendentious account providing little guidance as to why, even in the face of such criticism, so many have chosen to work on string theory. After reading this book and some of the unfortunate innuendo it contains, one might conclude not that string theorists are honest researchers doing the best they can to understand the nature of the universe, but rather are misguided devotees of a failed cult mired in self-delusion.

Posted at August 19, 2006 2:54 AM UTC

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71 Comments & 1 Trackback

Re: Not Even Wrong

Very nice review, fair and balanced.

One quip, the SuSy calculations on the CC while they do cut the problem in half are rather troubling, b/c in principle there is absolutely nothing wrong with the calculation. They seem robust! Whereas for the vanilla SM such a calculation is rather unnatural and one could speculate about all sorts of ways out of it. 120 orders of magnitude or 60 orders of magnitude is still (at least to my mind) god returning ‘error, man made mistake’

I think that is what Dr Woit was reffering too -shrug-

Posted by: Haelfix on August 19, 2006 6:40 AM | Permalink | Reply to this

Fine tuning

Whereas for the vanilla SM such a calculation is rather unnatural and one could speculate about all sorts of ways out of it.

Why is is more unnatural than the supersymmetric calculation? Because of the sensitivity to the UV cutoff?

120 orders of magnitude or 60 orders of magnitude is still (at least to my mind) god returning ‘error, man made mistake’

This reminds me of a (very minor) quibble I have with Aaron’s text. If one’s going to (correctly) note that the cosmological constant (in the absence of supersymmetry) is quartically-divergent, and hence the fine-tuning one part in 10 120, then one should say that the Higgs mass-squared is quadratically-divergent (in the absence of supersymmetry) and so the fine tuning is one part in 10 34.

[Aaron says it’s a fine tuning of one part in 10 17 of the mass, which is too generous a way of phrasing the problem; it’s the mass-squared that gets renormalized.]

Posted by: Jacques Distler on August 19, 2006 7:12 AM | Permalink | PGP Sig | Reply to this

Re: Fine tuning

Aaron says it’s a fine tuning of one part in 1017 of the mass, which is too generous a way of phrasing the problem; it’s the mass-squared that gets renormalized.

Very true. Thanx.

Posted by: Aaron Bergman on August 19, 2006 7:18 AM | Permalink | Reply to this

Re: Not Even Wrong

“Because of the sensitivity to the UV cutoff?”

Yea more or less. Also that the hamiltonian in globally supersymmetric field theory is an absolute quantity (related to the supercharges rather trivially with the antibracket) so the whole thing is calculated explicitly and rather trivially with a simple scalar potential and the vaccuum fluctuations.

You might worry that the setting is absurd as well, since all of this is flat spacetime calculations. The SUGRA calculation in curved spacetime thus is far more robust and you still retain the rather nice satisfying and clear form the hamiltonian has as well as the ease of the calculation. Its hard to imagine what went wrong.

Posted by: Haelfix on August 19, 2006 7:43 AM | Permalink | Reply to this

Re: Not Even Wrong

Err I should say the clear form the scalar potential (+kahler potential) possesses.

Posted by: Haelfix on August 19, 2006 7:49 AM | Permalink | Reply to this

Re: Not Even Wrong

Aaron,

It seems likely that the S.T. community can expect more of the kinds of critiques that are coming from Woit and Smolin. Woit has the advantage of not noisily promoting a particular alternative, and therefore being more likely to be seen as objective.

I think that outsiders are more likely to be convinced by thoughtful reviews of Peter’s book, such as the one you just posted, which explains your reasons for studying String Theory, rather than the outright dismissal of all opponents as crackpots, morons or losers.

Posted by: Chris Oakley on August 19, 2006 9:55 AM | Permalink | Reply to this

Re: Not Even Wrong

Aaron, thanks for the sensible review. I’ll try and write up a bit of a response on my blog.

Haelfix,

Yes, you’re right about the point I was trying to make. Before you bring in gravity, in the SM the vacuum energy is ill-defined, in a supersymmetric theory the vacuum energy is the order parameter for SSYM breaking and we know it has to have a scale of at least 100s of Gev. Your quantum gravity theory has to somehow have a plausible way of making this go away.

Especially given the other serious problems caused by supersymmetry breaking, this seems to me evidence that going to supersymmetric extensions of the SM doesn’t improve matters, but introduces new, intractable problems.

Posted by: Peter Woit on August 19, 2006 6:29 PM | Permalink | Reply to this

Re: Not Even Wrong

Before you bring in gravity, in the SM the vacuum energy is ill-defined

Before your bring in gravity, the vacuum energy is unmeasurable (not “ill-defined,” unmeasurable).

That is true whether or not the theory is supersymmetric.

[The fact that, in supersymmetric theories, there is a canonical choice of zero for this unmeasurable quantity is of no practical importance to anything.]

Once you do introduce gravity, then you have a something measurable to discuss.

Your quantum gravity theory has to somehow have a plausible way of making this go away.

And, as Haelfix points out, there’s 60 orders of magnitude more of a “miracle” that needs to take place in the non-supersymmetric case.

Posted by: Jacques Distler on August 19, 2006 8:23 PM | Permalink | PGP Sig | Reply to this

Re: Not Even Wrong

Jacques,

Your bizarre continuing insistence on correcting correct statements I make and ignoring the substance of my comments is truly remarkable.

“not “ill-defined,” unmeasurable”

“ill-defined” as stated is perfectly accurate, and implies “unmeasurable”.Sure, the fact that you can’t connect it to something measurable is why it’s ill-defined.

The substance of my comment, if you care to address it, was that the role of the vacuum energy as the order parameter for supersymmetry breaking causes a problem when you couple to gravity and want the measurable vacuum energy to be small.

And, as Haelfix points out, claiming that being off by 60 orders of magnitude instead of 120 as a point in favor of a theory is just silly.

Posted by: Peter Woit on August 19, 2006 9:20 PM | Permalink | Reply to this

Re: Not Even Wrong

“ill-defined” as stated is perfectly accurate, and implies “unmeasurable”.Sure, the fact that you can’t connect it to something measurable is why it’s ill-defined.

The substance of my comment, if you care to address it, was that the role of the vacuum energy as the order parameter for supersymmetry breaking

The vacuum energy is just as unmeasurable in a globally supersymmetric theory as in a nonsupersymmetric theory.

So the substance of your distinction (that the vacuum energy is “ill-defined” in the absence of supersymmetry) is incorrect.

Moreover, in supergravity (where there is actually a measurable question to ask), the vacuum energy is not an “order parameter” for supersymmetry-breaking. You can have unbroken supersymmetry with negative cosmological constant, or broken supersymmetry with zero cosmological constant or …

And, as Haelfix points out, claiming that being off by 60 orders of magnitude instead of 120 as a point in favor of a theory is just silly.

Nobody’s claiming that supersymmetric theories are a success in this regard. However, it is the converse claim: that a theory that is 120 orders of magnitude of is better than one that is 60 orders of magnitude off that is silly.

Posted by: Jacques Distler on August 19, 2006 9:33 PM | Permalink | PGP Sig | Reply to this

Re: Not Even Wrong

The distinction I was making between a globally supersymmetric theory and the SM was that in one case the expectation value of the Hamiltonian is an order parameter for supersymmetry breaking, and so can be connected to something measurable, in the other case it isn’t.

I’m well aware that this is no longer true in supergravity, and was careful to state this as a fact about flat space theories without gravity.

You continue to ignore the substance of my comment, choosing to drop it from what you quoted, here’s the full version again:

“The substance of my comment, if you care to address it, was that the role of the vacuum energy as the order parameter for supersymmetry breaking causes a problem when you couple to gravity and want the measurable vacuum energy to be small.”

So, is this true or not? Does the fact that superpartner splittings are at least 100s of GeVs cause a problem for getting a much smaller vacuum energy, or is this irrelevant?

“it is the converse claim: that a theory that is 120 orders of magnitude off is better than one that is 60 orders of magnitude off that is silly.”

Yes, but I never made this converse argument. Your fondness for ignoring arguments you can’t respond to, but instead making up stupid ones and putting them in the mouth of the person you are having a discussion with is quite remarkable.

Posted by: Peter Woit on August 19, 2006 10:22 PM | Permalink | Reply to this

Re: Not Even Wrong

You can’t have it both ways. Either you have gravity around and SUSY breaking scale is not the same as the cosmological constant, or there’s no gravity and the energy contribution of SUSY breaking is unmeasurable.

Posted by: Aaron Bergman on August 19, 2006 10:35 PM | Permalink | Reply to this

Re: Not Even Wrong

Aaron,

While in supergravity the SUSY breaking scale is not the same as the CC, I’m just not convinced that you’re not going to see effects of SUSY breaking in a calculation of the CC, even in supergravity.

Your theory should have a limit where you treat gravity semiclassically, and will you be able to avoid terms of the SUSY breaking scale showing up in the effective CC?

Can you point me to somewhere where someone does a realistic (including supersymmetry breaking) calculation of the CC? In such a calculation, do terms involving the SUSY breaking scale occur as part of the calculation or not?

Jacques,

Yes, maybe I’m wrong, but I do believe that the SUSY breaking scale terms that you have before you couple to gravity are relevant after you couple to gravity. You seem to agree that they’re going to be such terms in a calculation of the CC in supergravity. If you want to end up with a much smaller CC you’re going to have to cancel these somehow, and as far as I know there’s no natural way to do this. This is the problem that I’m talking about that you have in supersymmetric theories that you don’t have in non-supersymmetric ones.

I can assure you that in the book I don’t make your converse argument that being 120 orders of magnitude off is better than being 60 orders of magnitude off.

If you read Aaron’s review, you’ll see that what he takes me to task for is not claiming that the CC situation is better in the SM case, but for not mentioning that it also has the CC problem. I don’t say anything at all about the CC problem in the SM, do explain the problem in the supersymmetric case. Maybe he’s right that I should have said something more about this in the book.

This discussion began with me simply agreeing with Haelfix, who noted that there’s no useful distinction between being wrong by 60 vs. 120 orders of magnitude, and that the order of magnitude calculation is more robust and thus more troubling in the SUSY case.

I’m taking off for the evening. Maybe you two can argue with Haelfix, since all I was doing was agreeing with him.

Posted by: Peter Woit on August 19, 2006 11:33 PM | Permalink | Reply to this

Re: Not Even Wrong

It’s of course true that the breaking of SUSY does contribute to the vacuum energy (just as do many other things), but you cannot say that it equals the cosmological constant. My point was that you claimed that the cc problem is a strike against SUSY. The cc problem exists irrespective of whether or not your theory is supersymmetric, so I don’t see how your claim in the book makes sense.

Posted by: Aaron Bergman on August 20, 2006 12:39 AM | Permalink | Reply to this

Re: Not Even Wrong

Aaaron,

See Haelfix’s comment. I was not claiming that in supergravity models the CC comes purely from SUSY breaking. But you do get terms from SUSY breaking, and it is the fact that these are way too large that is why people claim that the theory has a CC problem. And the estimate of the minimal size of the SUSY breaking terms is robust due to the connection to superpartner mass splittings.

Posted by: Peter Woit on August 20, 2006 3:49 AM | Permalink | Reply to this

Re: Not Even Wrong

But you do get terms from SUSY breaking, and it is the fact that these are way too large that is why people claim that the theory has a CC problem.

No.

The CC problem is the fact that the various contributions (positive and negative) to the CC need to cancel to very high accuracy.

[The CC can perfectly well be, and usually is, nonzero even with unbroken SUSY.]

You have focussed on one particular contribution to the CC and said

Lookit how big it is! Bad SUSY. Bad!

If one, similarly, teased apart the various contributions to the CC in a non-supersymmetric theory, one would find terms which are much, much larger than the one you have focussed on.

As Aaron has said repeatedly, there is nothing about the CC problem that is special to supersymmetry. And, as Haelfix agrees, there’s no sense in which the problem is more acute in SUSY theories; if anything, supergravity is a tamer context for studying it.

The magnitude of the SUSY-breaking contribution sets a lower bound on how accurate the fine-tuning has to be.

Posted by: Jacques Distler on August 20, 2006 4:42 AM | Permalink | PGP Sig | Reply to this

Re: Not Even Wrong

“You have focussed on one particular contribution to the CC and said

Lookit how big it is! Bad SUSY. Bad!”

You know Jacques, it’s really a pathology with you, claiming I write things I didn’t write. It’s an unprofessional and intellectually unethical tactic to not deal with what someone actually writes, but to instead make up stupidly expressed sentences with bad grammar, put them in quotes, and claim this is the argument of your interlocutor. It may make you feel better and pleased with yourself for making the point of how ignorant and stupid I am, but it’s really pathetic behavior.

As for the rest of your comment, yes, the CC problem is the necessity of unnatural cancellations. But obviously the reason you need unnatural cancellations is that you have large terms that need to be cancelled.

For the N’th time, with N approaching infinity: there is something different about SUSY theories. They have contributions to the CC coming from supersymmetry breaking, and there is a robust argument for the size of these coming from superpartner mass splitting.

Posted by: Peter Woit on August 20, 2006 5:29 PM | Permalink | Reply to this

Re: Not Even Wrong

What exactly do you think happens to the vacuum energy in nonsupersymmetric theories?

Posted by: Aaron Bergman on August 20, 2006 5:40 PM | Permalink | Reply to this

Re: Not Even Wrong

For the N’th time, with N approaching infinity: there is something different about SUSY theories. They have contributions to the CC coming from supersymmetry breaking,

The only thing different about SUSY is your misapprehension that the vacuum energy vanishes in the absence of supersymmetry breaking.

In supergravity, even with unbroken supersymmetry, the vacuum energy is generically nonzero.

The fact that one has an estimate for the size of one particular contribution to the vacuum energy (the one coming from SUSY breaking) tells you nothing that you didn’t also know in nonsupersymmetric theories.

I’m really suprised that you continue to insist that there is a problem that arises in SUSY theories, with respect to the CC, that does not also arise in non-SUSY theories.

This is just false, and I hope it’s not indicative of the rest of the content of your book.

Posted by: Jacques Distler on August 20, 2006 6:04 PM | Permalink | PGP Sig | Reply to this

Re: Not Even Wrong

Jacques,

“your misapprehension that the vacuum energy vanishes in the absence of supersymmetry breaking”

For the n’th time, you may derive pleasure from making up things I didn’t write that you can construe as incorrect, but it’s dishonest, unprofessional and unethical. Any attempt to have a serious discussion with you is a complete waste of time.

Your inability to read what I write or even accurately quote it is just completely pathological.

As to what is different about the SUSY case, for the N+1st time:

“They have contributions to the CC coming from supersymmetry breaking, and there is a robust argument for the size of these coming from superpartner mass splitting.”

Hint: READ THE ENTIRE SENTENCE


Aaron,

I have no idea how to reliably compute the vacuum energy in non-supersymmetric theories, and don’t think anyone else does. Sure, to the extent the question is well-posed, one expects Planck scale contributions to the vacuum energy.

Posted by: Peter Woit on August 20, 2006 7:15 PM | Permalink | Reply to this

Re: Not Even Wrong

As to what is different about the SUSY case, for the N+1st time:

“They have contributions to the CC coming from supersymmetry breaking, and there is a robust argument for the size of these coming from superpartner mass splitting.”

So what? They determine, at worst, an upper bound on the value of the CC. This cannot possibly be construed as making the CC problem “worse” than in non-supersymmetric theories.

Despite all your bluster, you have utterly failed to make the case that the CC problem is somehow worse in supersymmetric theories.

As to whether I have misconstrued your statements on the subject, I will leave it to others to (re)read what you have written in this thread and draw their own conclusions.

Posted by: Jacques Distler on August 20, 2006 9:06 PM | Permalink | PGP Sig | Reply to this

Re: Not Even Wrong

“Despite all your bluster, you have utterly failed to make the case that the CC problem is somehow worse in supersymmetric theories.”

I seem to have at least finally gotten through to you that there is something different about the problem in the supersymmetric case, because it is linked to something we have an experimental handle on, superpartner mass splittings.

As for whether this makes the problem “worse”, you might want to notice that I never said that. I wrote no such thing in my book, and all I did here was agree with Haelfix’s first comment that this makes the problem more robust. Whether having a more robust problem is “worse” or “better” I’ll leave to others to decide.

Posted by: Peter Woit on August 20, 2006 9:48 PM | Permalink | Reply to this

Re: Not Even Wrong

I seem to have at least finally gotten through to you that there is something different about the problem in the supersymmetric case, because it is linked to something we have an experimental handle on, superpartner mass splittings.

No, the value of the cosmological constant is not “linked” to the strength of supersymmetry breaking, as Aaron (and everyone else) has pointed out to you.

One particular contribution to it (and not necessarily the dominant one) is linked (in a model-dependent way) to superpartner mass-splittings.

So what?

As for whether this makes the problem “worse”, you might want to notice that I never said that.

Oh. OK. I guess Aaron must have misunderstood you, too,

My point was that you claimed that the cc problem is a strike against SUSY. The cc problem exists irrespective of whether or not your theory is supersymmetric, so I don’t see how your claim in the book makes sense.

I can’t imagine where he would have gotten the impression that you think that the CC problem is a strike against supersymmetry.

This is the problem that I’m talking about that you have in supersymmetric theories that you don’t have in non-supersymmetric ones.

But thanks for clarifying your position.

I’m sure that the 0.01% of the readers of your book, who happen to stumble upon the the comments to this blog entry will be pleased to know that you think that supersymmetry isn’t responsible for the CC problem, but merely makes it “more robust.”

Posted by: Jacques Distler on August 21, 2006 4:03 AM | Permalink | PGP Sig | Reply to this

Re: Not Even Wrong

Jacques,

Readers of the book will read an explanation of how supersymmetry-breaking implies contributions to the CC that are 10^60 times too large, requiring unnatural cancellations to agree with the observed value and that serious particle theorists consider this to be a huge problem.

Readers of your commentary will learn that supersymmetry is wonderful because it improves the CC problem by a factor of 10^60.

In a nutshell, that’s why I wrote the book…

Posted by: Peter Woit on August 21, 2006 5:32 AM | Permalink | Reply to this

Re: Not Even Wrong

Readers of your commentary will learn that supersymmetry is wonderful because it improves the CC problem by a factor of 10^60.

Now who’s misquoting whom?

Nobody’s claiming that supersymmetric theories are a success in this regard.

Readers of the book will (apparently) come away with the misapprehension that the CC problem is a defect peculiar to supersymmetric theories.

That seems like a great disservice to them. Imagine their slack-jawed incredulity, if (as appears increasingly likely) the LHC discovers supersymmetry.

Positively painful to contemplate …

Posted by: Jacques Distler on August 21, 2006 6:10 AM | Permalink | PGP Sig | Reply to this

Re: Not Even Wrong

I’ll leave it to the readers here to decide whether your and Aaron’s comments might give someone the mistaken idea that you believe the fact that supersymmetry gets contributions to the CC from the TeV scale rather than the Planck scale is an argument in its favor.

It’s absolutely hilarious to be accused of spreading misinformation about supersymmetry by someone who then goes on to claim that the new Tevatron bounds on the Higgs make it “increasingly likely” that supersymmetry will be seen at LHC energies. This exciting piece of news doesn’t seem to have appeared elsewhere, I suggest you immediately contact the UT press office and have them prepare a press release about “new evidence for supersymmetry”.

Posted by: Peter Woit on August 21, 2006 3:08 PM | Permalink | Reply to this

Re: Not Even Wrong

I’ll leave it to the readers here to decide whether your and Aaron’s comments might give someone the mistaken idea that you believe the fact that supersymmetry gets contributions to the CC from the TeV scale rather than the Planck scale is an argument in its favor.

It is a fact that the cosmological constant problem is 10 60 times worse in the absence of low-energy supersymmetry. (I will repeat that this is not an argument in favour of supersymmetry.)

Since you, apparently, doubt this fact, let me present the argument.

Let us assume (counterfactually, but what the heck) that you are right: the severity of the cosmological constant problem is a function only of the supersymmetric mass splittings.

Let us start with conventional low-energy supersymmetry and start cranking up the scale of SUSY breaking. As we do so (or so your argument runs), the CC problem gets worse and worse. Eventually, as we push the SUSY breaking scale all the way up to near the Planck scale, the cosmological constant problem is 60 orders of magnitude worse than when we started.

But the theory that results (waggishly known as supersplit supersymmetry) is identical to the non-supersymmetric Standard Model.

It’s absolutely hilarious to be accused of spreading misinformation about supersymmetry by someone who then goes on to claim that the new Tevatron bounds on the Higgs make it “increasingly likely” that supersymmetry will be seen at LHC energies.

I think they make low energy SUSY more likely, because these bounds are very uncomfortable for various alternative theories of beyond-the-Standard-Model physics.

This exciting piece of news doesn’t seem to have appeared elsewhere,

Because, for those who’ve thought about these things, it’s not news.

I suggest you immediately contact the UT press office and have them prepare a press release about “new evidence for supersymmetry”.

I will leave the publicity-mongering to those with books to sell.

Posted by: Jacques Distler on August 21, 2006 3:49 PM | Permalink | PGP Sig | Reply to this

Re: Not Even Wrong

Jacques,

Thanks for the elaborate recounting of the obvious, together with the usual snide implication that I’ve not thought much about things.

This latest “evidence for supersymmetry” you’re helpfully promoting is just a classic example of the kind of overhype that has infected particle theory in recent years. Maybe someone should write a book about this…

Posted by: Peter Woit on August 21, 2006 4:18 PM | Permalink | Reply to this

Re: Not Even Wrong

Hi Jacques,

quite fun to come back from my summer vacations and find this diatriba going on! I must say I disagree with your statement… My pitch being that if MSSM is the theory, it will probably be the Tevatron the first facility where that ground will be broken!

As for the low Mt/high MW indications (1) indicating (2) LHC discoveries, the ellipse in the Mtop%MW plane only covers 68% of the C.L., which means that one third of the times the actual value of top, W, and Higgs masses lie outside of the circle… As an experimentalist, I have to say I love to speculate, but yours seems a (2)nd-level speculation and it seems far-fetched to me.

Cheers,
T.

PS I’d love if SUSY were found, unlike Peter ;-)
But like him, I doubt it will.

Posted by: Tommaso on August 22, 2006 7:29 PM | Permalink | Reply to this

Tevatron

My pitch being that if MSSM is the theory, it will probably be the Tevatron the first facility where that ground will be broken!

Hey, I’m all for healthy competition among the experimentalists!

If y’all think you can see SUSY first … :-)

More seriously, if the Higgs is as light as indications seem to be, then I understand the Tevatron probably will see see it first.

But it’s be hard to compete with the LHC as a “gluino factory”, no?

I have to say I love to speculate, but yours seems a (2)nd-level speculation and it seems far-fetched to me.

I don’t think it even rise to the level of a speculation. It’s just that the alternatives look rather ugly in light of these results. Relatively-speaking, SUSY looks better.

I’d love if SUSY were found, unlike Peter ;-)

But like him, I doubt it will.

Care to speculate on what you think will be found in its place?

Posted by: Jacques Distler on August 22, 2006 10:14 PM | Permalink | PGP Sig | Reply to this

Re: Tevatron

If the Tevatron excludes the Higgs mass from its domain, the whole thing becomes ugly (less so for MSSM, but still increasingly unnatural).

There are ways around it (say recent farfetched Higgs alternatives with heavy Gauge bosons) but they are also ugly in different ways. We really need to see *something* at least, especially for the LHC’s high energy runs.

Im not an expert on large extra dimensions, but aren’t there ways to get so called phenomenological desert and then a lot of activity without excessive finetuning? Perhaps that would be the logical best alternative in the case of no result. (please no Supersplit SUSY, that proposal is maximally ugly)

Posted by: Haelfix on August 23, 2006 8:15 AM | Permalink | Reply to this

Re: Tevatron

That maybe we’ll see “bulk perspective” as inherently tied to how we percieve that “extra energy[after calculating all the particle manifestations]” what’s left, as going into those “extra dimensions?”

Higgin’s(not “alice, ole hat”) now makes his appearance? He has a “strange personality” that people “flock” to him like people who gather to the professor crossing the room?

Posted by: Plato on August 23, 2006 5:04 PM | Permalink | Reply to this

Re: Not Even Wrong

“The substance of my comment, if you care to address it, was that the role of the vacuum energy as the order parameter for supersymmetry breaking …”

If the vacuum energy is unmeasurable, then it doesn’t serve as a useful order parameter for anything.

Is that clear?

I’m well aware that this is no longer true in supergravity, and was careful to state this as a fact about flat space theories without gravity.

But then you go on, in the same sentence, to say that this statement is relevant after coupling to gravity:

“… causes a problem when you couple to gravity and want the measurable vacuum energy to be small.”

which is wrong (an incorrect characterization of the nature of the cosmological constant problem in supergravity), for the simple reason that supersymmetry breaking is not the only contribution to the vacuum energy in supergravity.

Yes, but I never made this converse argument.

Perhaps (not having read your book) I was lead astray by Aaron’s review.

So you don’t assert that the cosmological constant problem is more acute in the supersymmetric case?

You agree that it is 60 orders of magnitude worse in the nonsupersymmetric case?

Posted by: Jacques Distler on August 19, 2006 10:52 PM | Permalink | PGP Sig | Reply to this

Re: Not Even Wrong

I realize this is splitting hairs and everyone knows this already and the statement is rather silly.

Its just that the SUGRA calculation is sort of the natural setting where you would think the CC problem would be well formulated. You have gravity and you can have curved space, and the statements are now measurable. And from an aesthetic point of view, its simply two terms that have to conspire to cancel to fantastic accuracy. All I was getting at, was that simple statement that it didn’t seem like there was much wiggle room there.

Posted by: Haelfix on August 19, 2006 11:53 PM | Permalink | Reply to this

Re: Not Even Wrong

This entire thread just reassures me that I made the right decision to leave physics and go to work on Wall Street :)

Posted by: Eric on August 21, 2006 6:06 AM | Permalink | Reply to this
Read the post More Scenes From the Storm in a Teacup, I
Weblog: Asymptotia
Excerpt: Aaron Bergman has written an extensive review of Peter Woit’s attack-book on string theory. I’ll let you read the thoughtfully written 11-page pdf document linked there. I think that Aaron deserves some sort of medal or other award for maki...
Tracked: August 21, 2006 8:18 AM

Re: Not Even Wrong

You know it is not easy for us lay people following these discussions.

If there has been some solifdification of the “points of view” here having read Aaron’s work, could there be a “short list” summarized/synopsized, as to why Peter’s book may not be suitable for/against the references to “string theory people” who are doing research in regards to quantum gravity?

As you know, some of us lay people are not that smart and could have easily fell under the spell of delusions, perpetrated by scientists for and against the use and advancement by way model apprehensions.:)


Posted by: Plato on August 21, 2006 10:45 PM | Permalink | Reply to this

Re: Not Even Wrong

I’m sorry, but I don’t understand the question. Regardless, pretty much all I want to say about Peter’s book is in the review. The discussion here has been about a single footnote there.

Posted by: Aaron Bergman on August 21, 2006 11:02 PM | Permalink | Reply to this

Re: Not Even Wrong

4 One particularly egregious example is in the discussion of the cosmological constant on pp. 178-9. It is true, as Dr. Woit states, that the cosmological constant as predicted by supersymmetric models is much
too large. What he neglects to mention, however, is that without supersymmetry (such as is the case in the standard model), the problem persists and is, in fact, many, many times worse.

Yes I see.

Like yourself once, me being only a private in the trenches watching the dialogues of generals, it was important that constructive criticisms be developed.

In all appearance this is what began I believe well intentionally then was diverted to the undertones that could color perceptions.

I took some offense to this as this was coming out of scientist creditialed with many witnesses’s abound.

So one’s look for important cirtticisms and constructive ones, like here, where the owness then is put back where it belonged in the first place to delve deeper into the issues that quantum gravity is displaying for us. Supersymmetry.

While you are engaging in the “laymans verse,” the resolutions are mathematically endowe, to disperse criticisms, and then, come back to share with us the socialogical outcome. Is this not the way?

As a mathematcian would those who would besmirch theoretics of strings, not give all the facts, instead suppementing us with a nice view of “crackpostism” and John’s Baez’s relevant point system, while we endeavor?

Sorry for my undertones:)

The “future of string theorists” would favour things to watch out for, not only all the maths involved.

Posted by: Plato on August 22, 2006 12:18 AM | Permalink | Reply to this

Re: Not Even Wrong

I’m sorry again, but I really can’t decipher what you’re saying.

Posted by: Aaron Bergman on August 22, 2006 12:21 AM | Permalink | Reply to this

Re: Not Even Wrong

This thread exhibits some remarkable self-similarity properties. Has anyone ever considered studying critical exponents of blog threads?

Posted by: anon. on August 22, 2006 2:12 AM | Permalink | Reply to this

Re: Not Even Wrong

exhibits some remarkable self-similarity properties

-you mean cosmologically, from a reductionistic point of view? :)

Posted by: Plato on August 22, 2006 3:41 AM | Permalink | Reply to this

The string concept

The first full paragraph on page 4 of Aaron’s review starts with

It is true [..] that there really is no such thing as ‘string theory’. It is, rather, a collection of partial theories and calculational techniques bound by physical intuition and conjecture.

I was surprised when I read this first. A “collection of partial theories bound by intuition and conjecture” does not sound like anything which would allow tests like described in the next sentence:

[…] this skein is remarkably robust. Calculations that have the possibility of destroying this structure invariably turn out to reinforce it.

Of course I immediately agree that the study of string theory involves a lot of partial theories, the links of which are often conjectural.

But I think it is important to point out that there is, apart from - and above - intuition and conjecture a binding force, which distinguishes the study of “string theory” from the study of a subjective menu of partial ideas that happen not to contradict each other.

Compare with some other field of physics. Say classical mechanics. There is a unifying essence, namely Newton’s laws, or Hamilton’s equations, if you like. People want to study this.

But only in the most simplest of situations can one actually practically study this essence itself. Most interesting phenomena in the world are - or at least have been for a considerable time of history - not directly accessibly using the fundamental equations. Often, they require inventing “new theories”, like thermodynamics, theory of friction, theory of fluid dynamics.

Today most of these “new theories” can be derived pretty well from first principles. But for various periods of history, scientists believed in the correctness of Newton’s laws but had to accompany them nevertheless by a “collection of partial theories and calculational techniques bound by physical intuition and conjecture”. Bound - that is - among each other, but, most importantly, bound by conjecture and intuition to the essence that they are thought to be derivable from in principle, namely some microscopic dynamics following Newton’s laws, or maybe following the laws of quantum mechanics, if that’s necessary.

If I remember correctly, there are aspects of something as ordinary as friction (certain special sorts of friction for certain materials) which even today remain puzzling, in that it is not clear precisely how they follow from a microscopic description.

The same case could be made for particle physics. While it is believed that the essence of particle physics is the study of the standard model, it is a fact of life that for describing most interesting phenomena, notably bound states of nucleons, one needs to resort to “theories ” (models) that are bound to the standard model only by intuition and conjecture. We expect them to be derivable from the essential concept itself, but we do not know how to do it.

I am emphasiziing this point because on the blogosphere one could frequently here various layman ask rethorically for “the equations” of string theory, implying precisely that the whole thing is made up from subjective choices without really being a “theory” which you could hand somebody with the words “this is what I mean by string theory, study this”. Like, for instance, you could do with classical gravity by handing somebody the Einstein-Hilbert functional.

For this reason it might be worthwhile to state clearly in a popular account like the above review is, what precisely it is in essence that people are studying when they are studying string theory, notwithstanding that this essence may incarnate itself in various different guises.

And - please correct me if you think I am wrong - the essence is this:

The study of string theory is the study of quantum theories that have a perturbative expansion which is given by a loop expansion in terms of Feynman-2-graphs computed using 2-dimensional gravity.

Whatever else you do, if it is not bound, maybe just by conjecture or intuition, to this essential principle, you will hardly be doing string theory.

For instance one can go ahead and study linearly-extended objects governed by an action principle involving a BF-theory (). Working out the dynamics, one finds that it does indeed describe propagation of string-like objects.

In a world where “string theory” would be just anything bound by intuition and conjecture, one could happily go ahead and declare that this particular theory is one of the many that constitute “string theory”.

But that’s not what happens. The dynamics of the strings in these BF-theories is not governed by Feynman-2-graphs with amplitudes governed by worldsheet gravity. So it’s something else, not “string theory”.

Of course it could happen, and I would be positively intrigued if it were true, that these BF-theory strings are related to one of the satellite theories that are indeed, slightly by conjecture and intuition, related to essential string theory proper: namely to the theory of D-branes and D-strings in particular.

With some “string theory” papers on DBI-actions and things like that, describing D-brane dynamics, one could get the impression that the theory investigated in these papers is just yet another random theory, that we happen to like to add into our “string theory” portfolio.

But of course this is not a matter of our free choice. The DBI-action, while it can be studied just by itself, is, by more or less robust arguments, believed to be derivable from the assumption that there is a theory whose perturbative expansion is given by a string theory S-matrix.

The same applies to all other topics studied in string theory. For instance, people are very interested in extensions of classical gravity which involve fields known as RR-fields. (Of course Aaron and Jacques know all this, much better than I do. I am just stating it for the record and for the general reader)

This is curious, as precisely for those fields it is not known how to relate such theories to a worldsheet description. But it is strongly believed that, while not known at the moment, it is possible in principle. Hence the “theory of RR-backgrounds” is related to the main body of string theory, partly by conjecture and intuition.

If, however, there were no indication at all that RR-backgrounds arise in quantum theories that have perturbatiuve expansion involving a string theory S-matrix, then we would not consider RR-backgrounds part of string theory. Would we?

Similar comments apply to Matrix Theory, AdS/CFT and so on.

I apologize for having probably emphasized the obvious. It just struck me as an important point in the discussion of the raison d’être of string theory.

Posted by: urs on August 22, 2006 10:52 AM | Permalink | Reply to this

Re: The string concept

Urs wrote:

For this reason it might be worthwhile to state clearly in a popular account like the above review is, what precisely it is in essence that people are studying when they are studying string theory, notwithstanding that this essence may incarnate itself in various different guises.

That’s a really interesting issue, but probably too subtle for a book review aimed at nonphysicists - for such an audience it would take at least a book.

And - please correct me if you think I am wrong - the essence is this:

The study of string theory is the study of quantum theories that have a perturbative expansion which is given by a loop expansion in terms of Feynman-2-graphs computed using 2-dimensional gravity.

See - you can say it in one sentence, but try explaining that sentence to your nonphysicist friends. Soon you’ll find you’ve written (or spoken) a book.

For instance one can go ahead and study linearly-extended objects governed by an action principle involving a BF-theory …

Been there, done that.

Working out the dynamics, one finds that it does indeed describe propagation of string-like objects.

In a world where “string theory” would be just anything bound by intuition and conjecture, one could happily go ahead and declare that this particular theory is one of the many that constitute “string theory”.

But that’s not what happens. The dynamics of the strings in these BF-theories is not governed by Feynman-2-graphs with amplitudes governed by worldsheet gravity. So it’s something else, not “string theory”.

Whew! You had me scared for a minute.

Seriously, I had a lot of trouble deciding whether I wanted to call these string-like objects “strings” or not, because of the political ramifications. At first I called them “loops”, because mathematically they’re just that. But, their role is completely unlike that of loops in loop quantum gravity, namely Wilson loops. Wilson loops also play a role in this paper, so it seemed too confusing to call these other guys “loops”. They actually resemble cosmic strings somewhat, insofar as they create a conical singularity in the metric. So, for lack of a better word I decided to call them strings, knowing full well that this would annoy certain people: loop quantum gravity people jumping to the conclusion that I’d “switched to string theory”, and string theorists jumping to the conclusion that I foolishly thought this stuff was “string theory” in the sense you describe.

Anyway, I think you’re right: the vast skein of ideas Aaron describes, which seems so amorphous and arbitrary to a complete outsider, does have a logic to it which motivates and guides the string theorist. But, explaining how this works even to other physicists would be a challenging book project. Nobody has written this book, so as string theorists march on in the absence of experimental success, a lot of physicists outside string theory are getting quite puzzled by what the string theorists are up to, and what they’re expecting to find.

Posted by: John Baez on September 9, 2006 5:57 PM | Permalink | Reply to this

Re: The string concept

That’s a really interesting issue, but probably too subtle for a book review aimed at nonphysicists

[…]

Anyway, I think you’re right: the vast skein of ideas Aaron describes, which seems so amorphous and arbitrary to a complete outsider, does have a logic to it which motivates and guides the string theorist. But, explaining how this works even to other physicists would be a challenging book project.

Agreed. I still think, though, that instead of writing

It is true [..] that there really is no such thing as ‘string theory’. It is, rather, a collection of partial theories and calculational techniques bound by physical intuition and conjecture.

one could for instance write something like

It is true [..] that there really is no such thing as a comprehensive formulation of ‘string theory’. It is, rather, a collection of partial theories and calculational techniques bound by physical intuition and conjecture to the central postulate that the scattering we measure in accelerators is computable in terms of certain, very specific, interactions of 1-dimensional objects.

I got the impression that to a large degree the discussion that Aaron’s review is in part a reaction to is not just about whether the idea of string theory may be right or wrong, but actually about whether following the idea of string theory in the first place is complete nonsense (“not science”).

So that’s why I thought, while I liked Aaron’s review a lot, the sentence in its original form is a little dangerous, because the attentive layman may well deduce from it precisely the message that there is no sensible guiding principle behind it all.

And this, I think, is quite wrong. The guiding principle behind perturbative string theory is quite strong and - apart from sociological reasons which certainly do play a (maybe even surprisingly large) role - the reason why it has attracted so much interest.

So even if some people (not all) make wild speculative, unfounded, wishful-thinking-like (maybe even obnoxious) claims about, say, the “landscape of vacua” - to name the example which plays the largest role of a source for criticism from Peter Woit - even then are they in fact - even if maybe in a bad heuristic physicist kind of way - even then are they trying to understand the implications of the one single well-motivated underlying principle of perturbative string theory.

I think this is important for understanding why so many people are willing to accept lots of hand-waving and heuristic arguments in string theory - because there is a well-defined (theoretical) entity at the heart of it all, which has complicated implications that lead - among other things - to complicated, heuristic, vague, “effective” partial theories that try to come to grips with aspects of this central principle.

I tried to compare this with the way different partial theories in classical mechanics (thermodynamics, fluid dynamics, etc.) all evolved around the central guiding principle of Newton’s equations. I believe this analogy is well suited to describe the role that speculation and hand-waving plays in string theory.

Seriously, I had a lot of trouble deciding whether I wanted to call these string-like objects “strings” or not, because of the political ramifications.

I think the best term would be “solitonic strings”. These are familiar (e.g. cosmic strings) from a couple of non-“string theoretic” field theories.

Posted by: urs on September 11, 2006 12:58 PM | Permalink | Reply to this

Re: Not Even Wrong


Unfortunately, I am a rogue student who needs lots of help sometimes. :)

All the points presented Urs, while demonstrating the materialization of “new methods (strings),” helps, not deters people from expanding the frontiers of science?

Historically, and most notably Newton and calculus?

So the method of maths gain ground when it is put into perspective. From Weinbergs first three mintues, to the microseconds that “strings constitue” in the expression of our universe? A microscopic/quantum analysis.

That, is advancement in our thinking. Qui! Non?

Where a dictionary proceeds in a circular manner, defining a word by reference to another, the basic concepts of mathematics are infinitely closer to an indecomposable element”, a kind of elementary particle” of thought with a minimal amount of ambiguity in their definition…also..Each generation builds a mental picture” of their own understanding of this world and constructs more and more penetrating mental tools to explore previously hidden aspects of that reality.

Posted by: Plato on August 22, 2006 4:19 PM | Permalink | Reply to this

Re: Not Even Wrong

It’s interesting to note the prominent String theorists reaction to books like
“Not Even Wrong” and “The Trouble With Physics”. Case in point, Lubos Motl’s “review” of Lee Smolins’s book - “The Trouble with Physics”. About all that Motl has to say in review is that
it is a very weird book, full of non-sense, that made him very angry. Probably that’s because string theory is a rather weird piece of nonsense itself, and now Lubos Motl and his motley crew of strung-out cohorts will have to find some new,
but equally irrelevant and mathematically
elegant pretense at doing physics.

Posted by: Kerri on September 2, 2006 9:01 PM | Permalink | Reply to this

Luboš

Please keep Luboš out of this.

He is

  1. Not a “prominent String theorist” (at least, not in the conventional sense).
  2. His behaviour has nothing to do with Aaron’s review, or the substantive issues under discussion here.

So, rather than let this discussion (like so many others) be derailed by bringing up LM, why don’t we stick to the issues, shall we?

Posted by: Jacques Distler on September 2, 2006 9:38 PM | Permalink | PGP Sig | Reply to this

Re: Not Even Wrong

I think it’s no fair to layfolk to say one has computed the entropy of black holes when one really means extremal or near-extremal black holes - purely theoretical entities that don’t exist in our universe. Layfolk would never guess you meant this. Why not just be clear?

Btw, I think somewhere you wrote “without precendence” when you meant “without precedents”.

Posted by: John Baez on September 9, 2006 7:27 AM | Permalink | Reply to this

Re: Not Even Wrong

I say the following:

“the calculations have been extended to a wide class of black holes (although, unfortunately, not to every possible black hole)”

which seems fair to me.

Posted by: Aaron Bergman on September 9, 2006 7:33 AM | Permalink | Reply to this

Re: Not Even Wrong

Aaron wrote:

I say the following:

“the calculations have been extended to a wide class of black holes (although, unfortunately, not to every possible black hole)”

which seems fair to me.

I’m sorry my first post sounded rather harsh - I was in a rush and didn’t really explain myself. Let me try to explain better.

You say your review is aimed at the general public rather than physicists. So, when reading it we have to pretend we’re not physicists.

If a nonphysicist hears that string theory has calculated the entropy for

a wide class of black holes (although, unfortunately, not every possible black hole)

they’ll think you mean something like

most black holes we see (but not those really weird ones in the Delta Quadrant)

They would never, ever guess you mean

lots of black holes that string theory predicts (but none like those we’ve ever seen)

I think if they read your review and later found out that’s what you meant, they’d be quite shocked and upset. They’d think they’d been fooled!

And they’d be sort of right, because in this one sentence you were putting the best face on things, instead of trying to explain things as clearly as possible to people who know little physics. And that’s a pity, because in general your review is very honest and avoids the temptation to put the best face on things.

You could avoid conveying a misleading impression by saying something like

a wide class of theoretically possible black holes (although, unfortunately, not those actually seen in nature)

Posted by: John Baez on September 9, 2006 4:52 PM | Permalink | Reply to this

Blackhole entropy

There are lots of things about the string calculations of blackhole entropy that don’t look like the real world.

Yes, the blackholes are usually extremal or near extremal. Far more relevant, however, is that all of them involve backgrounds where the dilaton is exactly massless. Indeed, the calculations are done in a regime where the VEV of the dilaton is such that the string scale is well below the Planck scale. And the vacuum has at least N=2 supersymmetry (8 unbroken supercharges).

That’s completely unlike the real world, where the dilaton surely is not massless, and supersymmetry is broken in the vacuum.

On the other hand, they are (in this unrealistic situation) ab initio computations of the degeneracy of micro-states of the system. They do not, for instance, assume that the relevant degrees of freedom are localized near the horizon. (If one makes that assumption, it’s hard to imagine how a computation of the entropy could fail to produce a result proportional to the area of the horizon.) And they get the numerical coefficient of the area (M pl 2/4) correct, even in the case of blackholes which are far from being supersymmetric.

I don’t know how to convey those subtleties to a lay audience.

But, let’s face it: the readership of The String Coffee Table is not exactly your run-of-the-mill lay audience.

Posted by: Jacques Distler on September 9, 2006 8:49 PM | Permalink | PGP Sig | Reply to this

Re: Blackhole entropy

[…] how to convey those subtleties to a lay audience.

For a “lay” audience familiar with basic principles of field theory, probably the important message here is that certain black holes (not those observed in our world, though) happen to have a perturbative description in perturbative string theory.

Hence the entropy calculations in perturbative string theory show that the formalism - while itself too restrictive (not non-perturbatively defined) to be applicable exactly to real-world black holes - does pass the necessary consistency checks in the domain of its strict applicability.

Posted by: urs on September 11, 2006 1:19 PM | Permalink | Reply to this

Re: Not Even Wrong

“the calculations have been extended to a wide class of black holes (although, unfortunately, not to every possible black hole)”

Alternatively, you could say that string theory can say something about unphysical (extremal or near-extremal) black holes, and that AdS/CFT is conjectured to relate unphysical (supersymmetric) Yang-Mills theory with string theory in a space with an unphysical (negative) sign of the cosmological constant.

Actually, I would have no problem with your formulation in isolation. However, when Aaron, and Brian Greene, and Bart Zwiebach, and every other string theorist systematically “forget” to mention any caveat for 20 years, it adds up to very lopsided and misleading view.

Posted by: Thomas Larsson on September 14, 2006 12:06 PM | Permalink | Reply to this

Unphysical

Alternatively, you could say that string theory can say something about unphysical (extremal or near-extremal) black holes, and that AdS/CFT is conjectured to relate unphysical (supersymmetric) Yang-Mills theory with string theory in a space with an unphysical (negative) sign of the cosmological constant.

A minor quibble: there are AdS/CFT backgrounds with no supersymmetry. But I take it that your point is broader.

Shall I understand that any mention of blackholes other than Schwarzschild ones, of spacetimes other than FRW cosmologies with positive cosmological constant, or of Quantum Field Theories other than the Standard Model must carry the warning label “Unphysical” lest one be accused of attempting to mislead the public?

Posted by: Jacques Distler on September 14, 2006 11:02 PM | Permalink | PGP Sig | Reply to this

Re: Unphysical

Jacques Distler writes:

Shall I understand that any mention of blackholes other than Schwarzschild ones, of spacetimes other than FRW cosmologies with positive cosmological constant, or of Quantum Field Theories other than the Standard Model must carry the warning label “Unphysical” lest one be accused of attempting to mislead the public?

Physicists spend a lot of time working with toy models that differ quite drastically from our universe. As long as these models have some features in common with our universe, they can be useful. Everyone posting here knows this. But nonphysicists don’t! So, since Aaron said he was aiming his review at “the general public”, we need to tackle the question you raise above:

Do we need to point out to nonphysicists that the string theory calculations of black hole entropy succeed so far only for black holes of sorts nobody has ever seen?

It certainly can’t hurt, because it’s an important part of the full story. One doesn’t need to get into technical details. One can just say that physicists are having so much trouble with quantum gravity that they spend a lot of time studying imaginary systems that resemble the black holes in our universe, but are easier to treat mathematically. So far, the successes of string theory concern these models.

Okay, so it can’t hurt. But do we need to do it?

It depends in part on how much importance is being claimed for these calculations.

Aaron is claiming as much importance as possible. He says finding the microstates responsible for black hole entropy is one of the “holy grails” of quantum gravity research. He adds that “no assumptions had to be made to obtain the correct result”.

Given this, cautions are in order.

When Aaron starts using “holy grail” imagery, nonphysicists will think he means the real thing we’ve been searching for all these years - not just a model we’re using as a warmup for the real thing. And, when he says “no assumptions had to be made to obtain the correct result”, nonphysicists would never guess he implicitly means “… except for various assumptions that do not hold for any actual black hole”.

Aaron’s one caution, that the calculations do not work for “every possible black hole”, doesn’t really clarify these points for his intended audience. It suggests that the calculations only fail for “exotic” black holes unlike the ones we usually see. In fact they only work for such black holes.

All this could be easily fixed by changing a few words here and there.


Posted by: John Baez on September 18, 2006 12:26 PM | Permalink | Reply to this

Re: Unphysical

The problem is, in part, that so many endeavors in current high energy physics are motivated rather indirectly.

The interest in black hole radiation and black hole entropy is not so much for phenomenological reasons. Lest some miracle happens, we have no chance at all of ever actually observing black hole radiation in the foreseeable future.

The interest in black hole entropy has always been something internal to theoretical physics. It’s a consistency check theory versus theory, not theory versus experiment.

Semiclassical reasoning associates to any kind of black hole, phenomenologically viable or not, an entropy. The idea is that a more complete quantum theory of gravity has to realize this entropy in terms of actual quantum states, no matter if the black hole state actually occurs in the observable universe, or not.

Since this is an issue of the internal behaviour of theories, people have always been very content with understanding it at least for some kinds of black holes.

And since progress in quantum gravity has been rather slow, all such “internal” consistency checks have received lots of attention.

Of course in the end the really interesting check is that which the avarage layman expects, namely the “external” consistency check with experiment.

The avarage layman tends to underestimate the difficulties this part of the game has. The average theoretician tends to forget that the average layman may not appreciate at all a consistency check internal to some theory.

So I guess it all depends on which audience you really want to address. If you really want to communicate with non-experts, John is right that all these things have to be made explicit.

And Jacques is right that we can hardly keep this level of explicitness in our average conversations.

And, by the way, this is not at all an issue just with string theory.

Just take a recent example: While not an expert, I did understand the central ideas of Alain Connes’ program to realize the standard model in terms of a spectral triple. But until the problem of fermion doubling had been solved just recently #, I was not aware that the Connes-Lott model actually failed to reproduce the observed physics for 1.5 decades. It just produces soemthing that came close enough to be of internal theoretical interest.

This was not a secret, but non-experts were likely to miss this point.

Posted by: urs on September 18, 2006 3:47 PM | Permalink | Reply to this

Re: Unphysical

In case this conversation is still alive, and since this particular complaint is pretty common, let me throw my two cents in.

I believe the present caveat, namely that the black holes for which the entropy (and many other quantities, but that is a different issue…) is calculated are not the astrophysical ones, is not usually mentioned because it is immaterial. The issues involved in black hole thermodynamics were never phenomenological in nature, rather the issue is exactly what a black hole is in a theory of quantum gravity and what does that tell us about such theory.

The exact counting suggests that there is a meaningful sense of black hole microscopics, and black hole is a complicated object made of many bits (like the fabled piece of coal). This was not obvious, different people had different mental pictures of black holes. If one wants to hold on to a such a different viewpoint of “astrophysical” black holes, at the very least now they have some explaining to do…

Precisely because of that view of black holes one would be surprised if an exact counting was available for all black hole (though one goes a long way using the correspondence principle to talk about more generic black holes). Again one does not doubt we have the correct mental picture of that piece of coal, even though we cannot calculate its thermodynamics quantities *precisely* from first principles.

Posted by: Moshe on September 18, 2006 4:54 PM | Permalink | Reply to this

Re: Unphysical

I believe the present caveat, namely that the black holes for which the entropy (and many other quantities, but that is a different issue…) is calculated are not the astrophysical ones, is not usually mentioned because it is immaterial. The issues involved in black hole thermodynamics were never phenomenological in nature, rather the issue is exactly what a black hole is in a theory of quantum gravity and what does that tell us about such theory.

Precisely so.

The fact that these blackholes differ (in various ways) from real astrophysical blackholes is utterly irrelevant, both observationally and theoretically.

There is an important theoretical question:

All blackholes have an associated Bekenstein-Hawking entropy. Are the ones for which we understand its microphysical origin sufficiently representative of the general case that we can relax and say “Now we truly understand (in general) the microphysical origin of the Bekenstein-Hawking entropy.”?

I happen to think the answer is, “No.” But this has absolutely nothing to do with the resemblance (or lack thereof) to astrophysical blackholes.

Indeed, to bring up astrophysical blackholes as the benchmark is, for the reasons Moshe stated, to confuse rather than to clarify the issue.

I don’t think doing so would be a service to the proverbial layman (who, in any case, does not seem to be in evidence hereabouts).

Posted by: Jacques Distler on September 18, 2006 6:00 PM | Permalink | PGP Sig | Reply to this

Re: Unphysical

Hi Jacques, I agree with you that it is premature to declare that we understand the microscopic origin of BH entropy for generic black holes. I think though that the evidence is now in favor of the viewpoint that there exists such microscopic explanation: again, we don’t understand all materials in nature, but we are pretty confident that their thermodynamics has *some* microscopic description, even if it unknown to us at present. Part of this confidence is experience with ideal gases and such, part of it is experimental input. In the present case, the latter is not going to come from astrophysical black holes…

Posted by: Moshe on September 18, 2006 6:44 PM | Permalink | Reply to this

Re: Unphysical

the proverbial layman (who, in any case, does not seem to be in evidence hereabouts).

Maybe he does not read this blog, but maybe he reads Aaron’s review of Peter Woit’s book and tries to figure out what is true and what is not.

But then again, maybe the conclusion is that with all books and reviews, the layman is bound to remain confused.

And maybe it’s even true.

Posted by: urs on September 18, 2006 7:14 PM | Permalink | Reply to this

Re: Unphysical

Hi All,

As a “proverbial layman” I thought I might add the following to the conversation:

1. While us “proverbial laymen and women” may not post very often, some of us are in fact lurking here in the background. Probably in significant numbers.

2. The apparent dishonesty exhibited by most string theorists, as is exemplified in this thread, can at times be breathtaking to behold. I say apparent but really with google and a short amount of time it is possible even for a layman to discern the truth in these matter, at least with respect to the honesty, respect, and professionalism by which the conversation is conducted.

3. In case Peter Woit is reading this (or another layman), I have read in a number of places the claim that the first part of his book might be difficult for someone such as myself to understand (I have a BS in engineering but have been in marketing and sales for the last 25 years). I did not find it so. Rather the material was helpful in putting the second part of the book into context. I found it well written and his arguments to be balanced and well articulated.

Thanks…I’ll go back to lurking now.

Posted by: Bob Hart on November 2, 2006 12:17 AM | Permalink | Reply to this

Hit and run

The apparent dishonesty exhibited by most string theorists, as is exemplified in this thread, can at times be breathtaking to behold.

Those are pretty strong words. Would you care to elaborate on the nature of the dishonesty you appear to have witnessed here?

I say apparent but really with google and a short amount of time it is possible even for a layman to discern the truth in these matter …

And the truth is …?

It’s all very well and good to level charges of dishonesty. But I think you owe it to those you are accusing to specify what it is that you think they are being dishonest about.

Posted by: Jacques Distler on November 2, 2006 1:46 AM | Permalink | PGP Sig | Reply to this

Re: Hit and run

Dear Jacques, fair enough…the nature of the dishonesty that I see is fairly plain in this thread. And hence my choosing to comment.

Baez and URS discuss above the context of ST claims vis-a-vis “blackholes” and how these are likely to be mis-interpreted by the general public. And since it appears that all of you experts agree as to what “blackholes” are and are not, the advise that given above would seem to be reasonable.

But you reject this point of view. Stating that it is “utterly irrelevant” and “to “confuse rather than to clarify the issue”. While this may be true “both observationally and theoretically” from the perspective of this thread and Aaron’s review your point of view is highly misleading to the average non-expert. And it is in this sense that I find it dishonest.

Posted by: Bob Hart on November 7, 2006 7:33 PM | Permalink | Reply to this

Re: Hit and run

I said in the review that string theory calculates the entropy of a wide class of black holes, but not for all of them.

From what we understand of string theory, it seems very unlikely that the understanding of the other types of black holes is conceptually different than the ones we currently understand. We just do not have the tools at this moment to calculate in more generic situations. If we could tackle such problems, it would probably represent a significant increase in our toolset and would be celebrated for that. The black hole entropy would then just be an application.

I tried very hard to be completely honest about the problems of string theory in that review, and I would not change the wording of that statement. Regardless, from a purely sociological point of view, the significance of the calculation of black hole entropy towards whether people believed string theory is on or not on the right track really can’t be overstated.

If you prefer it, I would say that string theory is the only theory of quantum gravity that has a fundmanetal derivation of the entropy of any black hole.

Posted by: Aaron Bergman on November 7, 2006 7:51 PM | Permalink | Reply to this

Re: Hit and run

A widely held believe is that a theory of quantum gravity should allow to compute exactly the entropy of all black holes.

Moshe # and Jacques # have however emphasized, that from the point of view of string theory this turns out to be a mislead expectation. They say that the insights (given you accept them) of string theory teach that it is wrong to expect there to be exact closed formulas for astrophysical black hole entropy.

They say this is not a failure of the theory, but instead one of the insights obtained from it: namely that there are different types of black holes that are to each other like, in solid state physics, a crystal is to a pice of charcoal.

The former admits closed formulas describing its properties, while the latter does not. And it’s not a failure of the theory that it does not, but instead a feature (since it characterizes important physical differences).

This is the point of view that has been obtained from studying string theory. But appreciating (or rejecting) it requires knowledge of quite bit of the general internals of string theory.

As with any sizable body of rather esoteric knowledge and/or conventions, statements by those familiar with details of that context may easily be honest and still completely misleading to anyone not aware of all the background.

Which - of course - does not mean that efforts to bridge the gap wouldn’t be useful.

Posted by: urs on November 7, 2006 9:43 PM | Permalink | Reply to this

Re: Hit and run

Moshe # and Jacques # have however emphasized, that from the point of view of string theory this turns out to be a mislead expectation. They say that the insights (given you accept them) of string theory teach that it is wrong to expect there to be exact closed formulas for astrophysical black hole entropy.

That’s a stronger statement than what I said. Current technology does not permit a computation of the entropy of astrophysical blackholes. I don’t know, one way or another, whether some future breakthrough would make that possible.

But, then, there are lots of things in Physics that we can only compute in somewhat idealized (or, to use the suggested pejorative, “unphysical”) situations.

The question is whether those computations are sufficiently representative of the “real” problem, that we feel we nonetheless understand what the answer should be.

In the case at hand, I said that I thought the answer was “no.”

But I emphasize that the thermodynamic properties of astrophysical blackholes are completely unobservable. So, while we should continue to be dissatisfied with our current string-theoretic understanding of blackhole entropy, astrophysical blackholes are not the reason why.

I am baffled that Mr. Hart thinks that’s “dishonest,” but there are many things that I find baffling about the “String Wars.”

Posted by: Jacques Distler on November 7, 2006 11:02 PM | Permalink | PGP Sig | Reply to this

Re: Unphysical

Moshe writes:

I believe the present caveat, namely that the black holes for which the entropy (and many other quantities, but that is a different issue…) is calculated are not the astrophysical ones, is not usually mentioned because it is immaterial. The issues involved in black hole thermodynamics were never phenomenological in nature, […]

Nobody is going to do experiments with black holes anytime soon, true. But I believe most of the entropy of the universe is already in the form of astrophysical black holes. So, it would be nice to have a theory that explained this, someday. String theory is not that theory yet.

You and Jacques say this is “immaterial” and “irrelevant”. But if string theory ever succeeds in explaining real-world black holes, I somehow doubt you’ll shrug and say this development doesn’t matter.

If you do, I’ll be impressed at your consistency.

Posted by: John Baez on October 2, 2006 1:57 AM | Permalink | Reply to this

Re: Unphysical

Hi John, I am not sure there is a way of moving the conversation forward in a productive way, looking forward to chatting about interesting physics sometime (maybe even black hole physics…).

Posted by: Moshe on October 2, 2006 9:17 PM | Permalink | Reply to this

Re: Not Even Wrong

I just finished reading this book. The author correctly describes the current status of string theory. However, he does not specify some achievements in other directions and how string theorists try to suppress these achievements. For more info about them visit http://archivefreedom.org/.

Also in page 181 he writes that “Einstein devoted most of his career to fruitless attempt to unify electromagnetism and gravity using the sort of geometric techniques that had worked in the case of GR.” However, in 2002 a Russian scientist (S. Shahverdiyev) formulated geometry underlyuing electromagnetism and proposed unified model of electromagnetism and gravitation using principle of geometrization, at least at the classical level. For detailes see hep-th/0205224.

Posted by: cheslav on April 13, 2007 10:35 PM | Permalink | Reply to this

Re: Not Even Wrong

There is a comment on the Not Even Wrong blog that it would be an achievement if string tension could predict the standard model particles. Lets look at this - string tension in a one-dimensional string is kx, where k is elasticity constant and x is displacement. Speed of a standing wave in a one-dimensional string is speed = sqrt(kx/mass-density), where mass density = mass-string/string-length. Take mass-string = mass universe = 10^53 Kg, string-length = Hubble radius = 10^26 meters, then take x = Hubble radius for first evaluation. Choose k = 7.18 x 10^17 for the time being. The speed for this case is speed = sqrt[(k/mass-universe)]Ru = 2.6 x 10^8 meters/sec = approximately c. Now if you think I chose k to match speed = c, think again. I started with the derivation below.

Assume all strings for standard-model particles have standing wave speed of c, only the mass-density changes. Now substitute in x = strong nuclear force range of 5.6x10^-15 meters and speed = c as before. The mass of the pi-meson(+) which mediates the strong nuclear force is found from c = sqrt[kx/(mass-pi_meson+/x)] = sqrt(k/mass-pi_meson+)x where x = 5.6x10^-15 meters as mentioned above. The result is mass-pi_meson+ = 2.5x10^-28 Kg or 140.7 MeV, close to the measured value. Next, keep the same speed (c) and change mass density for the weak nuclear force by substituting x = 10^-18 meters for range. The mass that results = 8 x 10^-36 meters or 4.5 eV, close to the 2.2 eV upper limit for the electron-neutrino as determined in the Mainz beta-decay experiments. Finally, take the x = planck length into this simple formula and find that mass = 2.04 x 10^-69 Kg, which in terms of energy is the largest compton wavelength possible (hc/lambda = mc^2, m = 2.04 x 10^-69 Kg, lambda = approx. Hubble radius).

Although I haven’t shown all particles (it’s left for the reader to try x = radius of electron, m = mass electron for instance), this simple formula for a one-dimensional string seems to get close for hadrons and fermions. A simplified differential equation is in the works for mesons, and a similar version of this concept is published in the journal of theoretics, vol. 6-5, “Quantum Foam”.

The point is, string theory should be simpler (after all, it’s a string!) and should predict a wide range of results if it’s elegant.

Posted by: Michael Harney on December 3, 2007 6:03 AM | Permalink | Reply to this

Re: Not Even Wrong

Any comments and corrections are greatly appreciated.

OK, Aaron, here goes :)

1) With 10^500 possible “string theories” one can easily say string theory predicts nothing. Indeed, when “Pope” Witten falsely claims ST “predicts gravity” it’s clearly a self-serving claim made to secure more funding. No, neither ST nor LQG actually “predict” gravity.

2. After 25+ years, ST has yet to make a SINGLE falsifiable prediction - it’s a dead-end.

3). Recently Lenny Suskind said that the existence of gravity, the existence of particles, and the existence of natural laws “prove” ST - what nonsense! The breath-taking lack of logic amazes me. He further went on to indulge in ad hominem attacks on Woit and Smolin. Personal attacks are apparently what string theorists do best, since they can’t produce any real science.

4). ST can’t even decide the dimensionality of space-time - is it 10,11,26, all of the above, none of the above?

5). “Stringers” claim the missing dimensions are rolled up into tiny CY manifolds too small to be measured. How convenient! The problem is real science deals with measureable properties. One might as well say some unobserved planet somewhere is made of green cheese…

Posted by: Jack on August 18, 2008 2:47 AM | Permalink | Reply to this

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