Comments on: More Scenes From the Storm in a Teacup, V http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/ Sat, 10 Jan 2009 01:35:06 +0000 http://wordpress.org/?v=2.5.1 By: Exploring QCD in Cambridge - Asymptotia http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-73152 Exploring QCD in Cambridge - Asymptotia Thu, 23 Aug 2007 04:10:21 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-73152 [...] The sad thing is (as I’ve pointed out many times before - for example in various seemingly pointless discussions with the largely ill-informed and misleading anti-string spokespeople last year, see e.g. here and here) that this is truly exciting physics where people from so many different approaches and persuasions are coming together in the spirit of getting insights into an exciting new physics problem - and you most likely won’t read about this conference in the press, because it is just not considered news to cover arguably one of the most exciting aspects of doing science - those times when good and useful ideas come from many, varied and sometimes unexpected directions. There’s fewer conflicts and controversies at times like this you see, and more in the way of cooperation and open-mindedness. All not, sad to say, considered urgent things to cover in a science story, even though most good science operates in this mode. Oh well. [...] [...] The sad thing is (as I’ve pointed out many times before - for example in various seemingly pointless discussions with the largely ill-informed and misleading anti-string spokespeople last year, see e.g. here and here) that this is truly exciting physics where people from so many different approaches and persuasions are coming together in the spirit of getting insights into an exciting new physics problem - and you most likely won’t read about this conference in the press, because it is just not considered news to cover arguably one of the most exciting aspects of doing science - those times when good and useful ideas come from many, varied and sometimes unexpected directions. There’s fewer conflicts and controversies at times like this you see, and more in the way of cooperation and open-mindedness. All not, sad to say, considered urgent things to cover in a science story, even though most good science operates in this mode. Oh well. [...]

]]> By: More Scenes From the Storm in a Teacup, VII - Asymptotia http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-33003 More Scenes From the Storm in a Teacup, VII - Asymptotia Tue, 13 Mar 2007 10:36:42 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-33003 [...] The beginnings (that I heard, at least) of breaking away from these frustratingly lame debates came when Lee Smolin debated Jeff Harvey (University of Chicago) on a Chicago radio show. I blogged a bit about it here and here and here. Sadly, although Jeff Harvey did a good job, given the circumstances, the debate did not really get as far with the content as would have been desirable before the show ran out of time. (We did have some excellent extended discussion on the latter two threads, including substantial contributions from Jeff Harvey and Jacques Distler, and on this thread, with substantial contributions by Mark Srednicki.) [...] [...] The beginnings (that I heard, at least) of breaking away from these frustratingly lame debates came when Lee Smolin debated Jeff Harvey (University of Chicago) on a Chicago radio show. I blogged a bit about it here and here and here. Sadly, although Jeff Harvey did a good job, given the circumstances, the debate did not really get as far with the content as would have been desirable before the show ran out of time. (We did have some excellent extended discussion on the latter two threads, including substantial contributions from Jeff Harvey and Jacques Distler, and on this thread, with substantial contributions by Mark Srednicki.) [...]

]]> By: Guest Blogger: Joe Polchinski on the String Debates | Cosmic Variance http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-7313 Guest Blogger: Joe Polchinski on the String Debates | Cosmic Variance Thu, 07 Dec 2006 05:39:24 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-7313 [...] You may have read here and there about the genteel discussions concerning the status of string theory within contemporary theoretical physics. We’ve discussed it on CV here, here, and even way back here, and Clifford has hosted a multipart discussion at Asymptotia (I, II, III, IV, V, VI). [...] [...] You may have read here and there about the genteel discussions concerning the status of string theory within contemporary theoretical physics. We’ve discussed it on CV here, here, and even way back here, and Clifford has hosted a multipart discussion at Asymptotia (I, II, III, IV, V, VI). [...]

]]> By: More Scenes From the Storm in a Teacup, VI - Asymptotia http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3876 More Scenes From the Storm in a Teacup, VI - Asymptotia Fri, 10 Nov 2006 15:44:53 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3876 [...] I’ll leave it to you to form your own opinion about Smolin’s remarks (I’ve not had time to read it in detail yet), and start a discussion here. Maybe ask him some followup questions here, for example. To help with context and build a more complete picture, do read some of the earlier comments and discussions involving him -and questions put directly to him- on the threads that share the name of this post. (e.g., Here and here.) Put those alongside the discussion with Peter Woit and of the central thesis of Woit’s book too. They are inseparable. [...] [...] I’ll leave it to you to form your own opinion about Smolin’s remarks (I’ve not had time to read it in detail yet), and start a discussion here. Maybe ask him some followup questions here, for example. To help with context and build a more complete picture, do read some of the earlier comments and discussions involving him -and questions put directly to him- on the threads that share the name of this post. (e.g., Here and here.) Put those alongside the discussion with Peter Woit and of the central thesis of Woit’s book too. They are inseparable. [...]

]]> By: Not Even Wrong » Blog Archive » String Wars, Part Deux http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3309 Not Even Wrong » Blog Archive » String Wars, Part Deux Sat, 04 Nov 2006 17:51:32 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3309 [...] Yesterday at the KITP in Santa Barbara, George Johnson gave a second talk and led a discussion on the subject of the “String Wars”. The rather remarkable first session was discussed here, here and here. This time people were much better behaved, and the main topic was the media coverage of physics in general, and the past history of the media interest in string theory, and what effects this might have had. [...] [...] Yesterday at the KITP in Santa Barbara, George Johnson gave a second talk and led a discussion on the subject of the “String Wars”. The rather remarkable first session was discussed here, here and here. This time people were much better behaved, and the main topic was the media coverage of physics in general, and the past history of the media interest in string theory, and what effects this might have had. [...]

]]> By: Clifford http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3137 Clifford Wed, 01 Nov 2006 19:13:28 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3137 Tony Smith, Please think what you want about my policy. Thanks. -cvj Tony Smith,

Please think what you want about my policy.

Thanks.

-cvj

]]> By: Tony Smith http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3131 Tony Smith Wed, 01 Nov 2006 18:38:38 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3131 Clifford, you said "... When it comes to matters of race and gender, among other topics, I [Clifford] find myself unwilling to look at, or to point others in, the direction of rather deliberately objectionable writings on the subjects. ...". Isn't failing to "look at ... objectionable writings" an ostrich head-in-the-sand approach? If you don't "look at" the bad stuff, and also don't "point others ... in the direction of" the bad stuff to show them that it exists and how bad it is, then aren't you aiding the bad guys by hiding from them instead of confronting them ? Or, are you just trying to protect your fellow superstringer Harvard Professor Motl by trying to limit discussion about what he is saying on his blog ? Tony Smith http://www.valdostamuseum.org/hamsmith/ Clifford, you said “… When it comes to matters of race and gender, among other topics, I [Clifford] find myself unwilling to look at, or to point others in, the direction of rather deliberately objectionable writings on the subjects. …”.

Isn’t failing to “look at … objectionable writings” an ostrich head-in-the-sand approach?

If you don’t “look at” the bad stuff,
and also
don’t “point others … in the direction of” the bad stuff to show them that it exists and how bad it is,
then
aren’t you aiding the bad guys by hiding from them instead of confronting them ?

Or, are you just trying to protect your fellow superstringer Harvard Professor Motl by trying to limit discussion about what he is saying on his blog ?

Tony Smith
http://www.valdostamuseum.org/hamsmith/

]]> By: Mark Srednicki http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3120 Mark Srednicki Wed, 01 Nov 2006 17:19:47 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3120 JZ, I've read through the parts of Lee's book that are relevant to the debate, and skimmed the rest. (I believe that, for example, I know the history of particle physics well enough not to need to read Lee's version closely.) I have also heard Lee and othes working on LQG speak many times, read a number of their papers, and followed some of the recent technical debate at the String Coffee Table and Jacques Distler's blog. I have not read Peter Woit's book, and have not commented on it, here or elsewhere. JZ, I’ve read through the parts of Lee’s book that are relevant to the debate, and skimmed the rest. (I believe that, for example, I know the history of particle physics well enough not to need to read Lee’s version closely.) I have also heard Lee and othes working on LQG speak many times, read a number of their papers, and followed some of the recent technical debate at the String Coffee Table and Jacques Distler’s blog. I have not read Peter Woit’s book, and have not commented on it, here or elsewhere.

]]> By: Peter Woit http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3117 Peter Woit Wed, 01 Nov 2006 16:26:26 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3117 Clifford, Again: I acknowledge that I sometimes make mistakes, and if that's the case here, I'm more than willing to try and correct the record and issue any appropriate apologies. I can't do this if I don't know what it is that you are claiming that I got wrong. In this case you continue to be unwilling to communicate to me what the mistake in question is supposed to be and instead seem intent on pursuing it purely as a way of tarring me as dishonest, in particular using it to claim that my criticisms of string theory are dishonestly made. This tactic strikes me as, well, dishonest. Clifford,

Again: I acknowledge that I sometimes make mistakes, and if that’s the case here, I’m more than willing to try and correct the record and issue any appropriate apologies. I can’t do this if I don’t know what it is that you are claiming that I got wrong. In this case you continue to be unwilling to communicate to me what the mistake in question is supposed to be and instead seem intent on pursuing it purely as a way of tarring me as dishonest, in particular using it to claim that my criticisms of string theory are dishonestly made. This tactic strikes me as, well, dishonest.

]]> By: Aaron Bergman http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3114 Aaron Bergman Wed, 01 Nov 2006 15:25:47 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3114 I've read all of Peter Woit's book. I've also read chapters 16,18,19,20 of Lee Smolin's book and skimmed the rest. It's worth pointing out that both Lee and Peter have participated in these various internet fora for a while now, so it's not as if either of their positions on various subjects are unknown. I’ve read all of Peter Woit’s book. I’ve also read chapters 16,18,19,20 of Lee Smolin’s book and skimmed the rest.

It’s worth pointing out that both Lee and Peter have participated in these various internet fora for a while now, so it’s not as if either of their positions on various subjects are unknown.

]]> By: JZ http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3113 JZ Wed, 01 Nov 2006 15:20:44 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3113 To Jacques Distler, Have you read Lee Smolin's or Peter Woit's book? To Mark Srednicki, Have you read Lee Smolin's or Peter Woit's book? I am just curious to what extend one side of the debate knows the position of the other side. To Jacques Distler,

Have you read Lee Smolin’s or Peter Woit’s book?

To Mark Srednicki,

Have you read Lee Smolin’s or Peter Woit’s book?

I am just curious to what extend one side of the debate knows the position of the other side.

]]> By: Clifford http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3103 Clifford Wed, 01 Nov 2006 13:12:32 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3103 When it comes to matters of race and gender, among other topics, I find myself unwilling to look at, or to point others in, the direction of rather deliberately objectionable writings on the subjects. I'd rather not have links to that sort of material either. I don't have a policy against links in general. Best, -cvj When it comes to matters of race and gender, among other topics, I find myself unwilling to look at, or to point others in, the direction of rather deliberately objectionable writings on the subjects. I’d rather not have links to that sort of material either.

I don’t have a policy against links in general.

Best,

-cvj

]]> By: TheGraduate http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3100 TheGraduate Wed, 01 Nov 2006 12:35:59 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3100 Dr. Johnson, About the links, I didn't know there was a policy about that sort of thing. Can you tell me what your policy is? Dr. Johnson,

About the links, I didn’t know there was a policy about that sort of thing. Can you tell me what your policy is?

]]> By: Jacques Distler http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3092 Jacques Distler Wed, 01 Nov 2006 07:33:57 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3092 I am, indeed, going to restrict myself to spacetimes with timelike conformal boundaries. And one is, indeed, (severely) restricted in what initial data can be evolved forward without leading to a big crunch. All of these feature are incorporated in the AdS/CFT conjecture, as clarified by Witten and by Gubser-Klebanov-Polyakov, following on Maldacena's original suggestion. Of course, I'm not (just) interested in things which have a semiclassical description in terms of smooth supergravity solutions. One generalization is to consider boundary conditions which correspond to relevant perturbations of the boundary CFT. Even semiclassically, these do not give rise to smooth interior geometries. But they can have interesting descriptions in the full string theory. And if the magnitude of the cosmological constant is not small (in Planck units), then, even in the case of an exactly conformal boundary, the bulk theory is far from being well-described by semiclassical supergravity. But, before wandering off into such topics, one should --- at least --- have a formalism which, in an appropriate limit, reproduces known features of the semiclassical physics. And, like you, I don't see how such a formalism could <em>possibly</em> be "background independent," in the sense Lee would like to use the term. I am, indeed, going to restrict myself to spacetimes with timelike conformal boundaries. And one is, indeed, (severely) restricted in what initial data can be evolved forward without leading to a big crunch.

All of these feature are incorporated in the AdS/CFT conjecture, as clarified by Witten and by Gubser-Klebanov-Polyakov, following on Maldacena’s original suggestion.

Of course, I’m not (just) interested in things which have a semiclassical description in terms of smooth supergravity solutions.

One generalization is to consider boundary conditions which correspond to relevant perturbations of the boundary CFT. Even semiclassically, these do not give rise to smooth interior geometries. But they can have interesting descriptions in the full string theory.

And if the magnitude of the cosmological constant is not small (in Planck units), then, even in the case of an exactly conformal boundary, the bulk theory is far from being well-described by semiclassical supergravity.

But, before wandering off into such topics, one should — at least — have a formalism which, in an appropriate limit, reproduces known features of the semiclassical physics.

And, like you, I don’t see how such a formalism could possibly be “background independent,” in the sense Lee would like to use the term.

]]> By: TheGraduate http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3087 TheGraduate Wed, 01 Nov 2006 05:07:18 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3087 Hello Dr. Srednicki: On the issue of disparaging views of minorities and women held by physicists at good universities, you can take a look at the following if you wish (also I suggest reading the comment section): <em>[Links to motl's blog removed by cvj]</em> I think, if Dr. Johnson has some kind of spam detection, it might kill my post if I add any more links so I will stop here. Hello Dr. Srednicki:

On the issue of disparaging views of minorities and women held by physicists at good universities, you can take a look at the following if you wish (also I suggest reading the comment section):

[Links to motl's blog removed by cvj]

I think, if Dr. Johnson has some kind of spam detection, it might kill my post if I add any more links so I will stop here.

]]> By: gerry atric http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3086 gerry atric Wed, 01 Nov 2006 04:49:26 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3086 "If you don’t nail down the asymptotic behaviour of the metric, you don’t have a well-posed initial value problem, even classically. Once you specify appropriate boundary conditions, however, you obtain a hyperbolic problem." I'm not sure I get you, sorry. The initial value problem in GR asks you to specify a metric, energy density, extrinsic curvature etc. *everywhere* on an initial slice. [I know you know this, just stating it so we are not talking about different things.] A typical spatial slice for AdS would be a 3D space of constant negative curvature. Now it seems to me [wrongly?] that what you are saying is that it is ok to deform this metric deep in the interior, provided that the 3D metric still has approximately constant negative curvature far away. Then the system will evolve to something like "AdS deformed deep in the bulk" but still asymptotically AdS; intuitively, the conformal boundary of the 3D negatively curved space evolves into the timelike conformal boundary of the deformed AdS. But is all this really true? Won't the evolution lead to a Big Crunch, generically? The point is that non-globally-hyperbolic spacetimes like AdS *cannot* usually be obtained by the usual evolution from initial data. The existence theorem guarantees the existence of an essentially unique *globally hyperbolic* solution of the field equations, but that unique solution won't be the spacetime we want, except in the case of *exact* AdS [where the maximal Cauchy development can be analytically continued to all of AdS]. Note that the singularity theorems apply here! Actually all this is what I had in mind when I asked Prof Smolin what he could possibly mean by a *fully* background free formulation of the AdS/CFT setup. Background-free here can't mean what he wants it to mean, because you can't treat asymptotically AdS spacetimes as if they were cosmological models. The best you can do is to agree at the outset that you are only going to talk about spacetimes with timelike conformal boundaries --- which I think is what you are saying. “If you don’t nail down the asymptotic behaviour of the metric, you don’t have a well-posed initial value problem, even classically. Once you specify appropriate boundary conditions, however, you obtain a hyperbolic problem.”

I’m not sure I get you, sorry. The initial value problem in GR asks you to specify a metric, energy density, extrinsic curvature etc. *everywhere* on an initial slice. [I know you know this, just stating it so we are not talking about different things.] A typical spatial slice for AdS would be a 3D space of constant negative curvature. Now it seems to me [wrongly?] that what you are saying is that it is ok to deform this metric deep in the interior, provided that the 3D metric still has approximately constant negative curvature far away. Then the system will evolve to something like “AdS deformed deep in the bulk” but still asymptotically AdS; intuitively, the conformal boundary of the 3D negatively curved space evolves into the timelike conformal boundary of the deformed AdS.

But is all this really true? Won’t the evolution lead to a Big Crunch, generically? The point is that non-globally-hyperbolic spacetimes like AdS *cannot* usually be obtained by the usual evolution from initial data. The existence theorem guarantees the existence of an essentially unique *globally hyperbolic* solution of the field equations, but that unique solution won’t be the spacetime we want, except in the case of *exact* AdS [where the maximal Cauchy development can be analytically continued to all of AdS]. Note that the singularity theorems apply here!

Actually all this is what I had in mind when I asked Prof Smolin what he could possibly mean by a *fully* background free formulation of the AdS/CFT setup. Background-free here can’t mean what he wants it to mean, because you can’t treat asymptotically AdS spacetimes as if they were cosmological models. The best you can do is to agree at the outset that you are only going to talk about spacetimes with timelike conformal boundaries — which I think is what you are saying.

]]> By: Jacques Distler http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3084 Jacques Distler Wed, 01 Nov 2006 04:04:03 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3084 <blockquote>Relatedly: I keep seeing the words globally hyperbolic. AdS isn’t globally hyperbolic, so I don’t quite see what is being claimed.</blockquote> Exactly the point! If you don't nail down the asymptotic behaviour of the metric, you don't have a well-posed initial value problem, even classically. Once you specify appropriate boundary conditions, however, you obtain a hyperbolic problem. You can have a theory that is background independent, to the extent that you don't have to specify a background metric (over the "interior of AdS"). But you can't avoid the necessity of specifying the asymptotic behaviour of the metric. This requirement, which is basic to the formulation of AdS/CFT, is generic to any would-be quantum theory of gravity in asymptotically AdS space.

Relatedly: I keep seeing the words globally hyperbolic. AdS isn’t globally hyperbolic, so I don’t quite see what is being claimed.

Exactly the point!

If you don’t nail down the asymptotic behaviour of the metric, you don’t have a well-posed initial value problem, even classically. Once you specify appropriate boundary conditions, however, you obtain a hyperbolic problem.

You can have a theory that is background independent, to the extent that you don’t have to specify a background metric (over the “interior of AdS”). But you can’t avoid the necessity of specifying the asymptotic behaviour of the metric. This requirement, which is basic to the formulation of AdS/CFT, is generic to any would-be quantum theory of gravity in asymptotically AdS space.

]]> By: Mark Srednicki http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3082 Mark Srednicki Wed, 01 Nov 2006 03:36:53 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3082 Lee, I do accept your apology. Of course I would not expect anyone to walk away from a signed contract, but I agree with Clifford that each of us is responsible for the ultimate results of contracts we sign. And just to be clear, the issue is not "advertising copy", but rather the subtitle of the book, a subtitle that amazon, barnesandnoble, and bordersstores all display as part of the title itself. As for prejudice in physics, you wrote that "blatant prejudice" is responsible for the relatively small numbers of women and blacks, and that anyone who claims (as I do) not to have seen "naked prejudice" in action is "blind" or "dishonest". You now seem to be backing off from these claims, using the rather milder phrase "unconscious prejudice". Precision in language in discussing hot-button issues is something we should all strive for. Lee, I do accept your apology. Of course I would not expect anyone to walk away from a signed contract, but I agree with Clifford that each of us is responsible for the ultimate results of contracts we sign. And just to be clear, the issue is not “advertising copy”, but rather the subtitle of the book, a subtitle that amazon, barnesandnoble, and bordersstores all display as part of the title itself.

As for prejudice in physics, you wrote that “blatant prejudice” is responsible for the relatively small numbers of women and blacks, and that anyone who claims (as I do) not to have seen “naked prejudice” in action is “blind” or “dishonest”. You now seem to be backing off from these claims, using the rather milder phrase “unconscious prejudice”. Precision in language in discussing hot-button issues is something we should all strive for.

]]> By: gerry atric http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3081 gerry atric Wed, 01 Nov 2006 03:34:53 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3081 Sorry, maybe somebody can clarify things for me. It seems to me that LS is saying that any theory that insists from the outset on using asymptotically AdS spacetimes is not *completely* background-free, which seems pretty reasonable until you ask: what would a completely background-free description of this situation look like? Relatedly: I keep seeing the words globally hyperbolic. AdS isn't globally hyperbolic, so I don't quite see what is being claimed. Sorry, maybe somebody can clarify things for me. It seems to me that LS is saying that any theory that insists from the outset on using asymptotically AdS spacetimes is not *completely* background-free, which seems pretty reasonable until you ask: what would a completely background-free description of this situation look like?

Relatedly: I keep seeing the words globally hyperbolic. AdS isn’t globally hyperbolic, so I don’t quite see what is being claimed.

]]> By: Clifford http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3078 Clifford Wed, 01 Nov 2006 03:14:42 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3078 Please interfere.... not a problem. It is ok for us to disagree on the previous, if you wish. Cheers, -cvj Please interfere…. not a problem. It is ok for us to disagree on the previous, if you wish.

Cheers,

-cvj

]]> By: TheGraduate http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3074 TheGraduate Wed, 01 Nov 2006 02:37:55 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3074 Dr. Johnson, Sorry, I really didn't mean to interfere too much. I was just hoping to promote some good faith discussion. Dr. Johnson,

Sorry, I really didn’t mean to interfere too much. I was just hoping to promote some good faith discussion.

]]> By: Jacques Distler http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3071 Jacques Distler Wed, 01 Nov 2006 01:45:47 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3071 ‘When I use a word,’ Humpty Dumpty said in rather a scornful tone, ‘it means just what I choose it to mean—neither more nor less.’ <blockquote>“The strongest possible form of background independence consistent with quantum gravity in asymptotically anti-de Sitter spacetimes.” according to you, does not satisfy the standard definition of background independence</blockquote> Sorry, Lee, but unlike Humpty Dumpty, Physics does not allow us to choose what "background independence" in asymptotically anti-de Sitter spacetimes is supposed to mean. If what is allowed by the Physics doesn't accord with your "definition", then that is an inadequacy of your definition. This has nothing to do with the correctness (or completeness or whatever) of Maldacena's Conjecture. Maldacena's Conjecture could be <em>completely wrong</em>. That still would not pave the way for a "more background independent" theory of quantum gravity in asymptotically anti-de Sitter space. If you want to insist that <em>any theory</em> of quantum gravity in asymptotically anti-de Sitter space obeys only a "weak form of background independence," go right ahead. But to insist that AdS/CFT suffers from this defect (with the implication that some alternative theory would not) is dishonest. That is not meant as a slam, or as an insult. If David Gross misrepresented (or misremembered or misinterpreted) your conversation in July, that's unfortunate, but it's something you'll have to take up with him. It doesn't change the physics one iota. And, I have to say, I am rather disappointed at the arc of our conversation about the latter. ‘When I use a word,’ Humpty Dumpty said in rather a scornful tone, ‘it means just what I choose it to mean—neither more nor less.’

“The strongest possible form of background independence consistent with quantum gravity in asymptotically anti-de Sitter spacetimes.” according to you, does not satisfy the standard definition of background independence

Sorry, Lee, but unlike Humpty Dumpty, Physics does not allow us to choose what “background independence” in asymptotically anti-de Sitter spacetimes is supposed to mean. If what is allowed by the Physics doesn’t accord with your “definition”, then that is an inadequacy of your definition.

This has nothing to do with the correctness (or completeness or whatever) of Maldacena’s Conjecture. Maldacena’s Conjecture could be completely wrong. That still would not pave the way for a “more background independent” theory of quantum gravity in asymptotically anti-de Sitter space.

If you want to insist that any theory of quantum gravity in asymptotically anti-de Sitter space obeys only a “weak form of background independence,” go right ahead. But to insist that AdS/CFT suffers from this defect (with the implication that some alternative theory would not) is dishonest.

That is not meant as a slam, or as an insult.

If David Gross misrepresented (or misremembered or misinterpreted) your conversation in July, that’s unfortunate, but it’s something you’ll have to take up with him. It doesn’t change the physics one iota. And, I have to say, I am rather disappointed at the arc of our conversation about the latter.

]]> By: Elliot http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3061 Elliot Tue, 31 Oct 2006 23:55:28 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3061 Mark, Sure everything is negotiable if you prepared to walk... But in good faith negotiations there is give and take. What is very clear to me is that this thread itself is not "background independent" ;) Elliot Mark,

Sure everything is negotiable if you prepared to walk… But in good faith negotiations there is give and take.

What is very clear to me is that this thread itself is not “background independent” ;)

Elliot

]]> By: Lee Smolin http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3058 Lee Smolin Tue, 31 Oct 2006 23:47:26 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3058 Jacques, "The strongest possible form of background independence consistent with quantum gravity in asymptotically anti-de Sitter spacetimes." according to you, does not satisfy the standard definition of background independence (or in Greene's terms, manifest background independence) which is that no classical metric and no global symmetries are required to state the laws of the theory. But it does satisfy something weaker than that and because I respect the facts I have been careful in speaking and writing to state clearly the situation. I don't argue from my feelings, when there is a clear logical case for something I acknowledge it and try to state it clearly. It seems like the pay back I get for trying to be accurate about the facts and precise in my characterization of them is to get insulted and slammed by people who deliberately twist a subtle distinction to make it look like a contradiction. I am still waiting for someone to acknowledge that they had the impression that I did not mention in the book that the Maldacena conjecture could satisfy some (any!) form of background independence, and that, having read the quote from the book, they recognize that impression was wrong. I would like to get some recognition of the fact that on many issues, including this one, my book describes the factually correct situation. Dear Mark, I accept your apology, I hope you can accept mine. In fact, one cannot walk away from a contract signed years earlier a few weeks before publication over a dispute over advertising copy, without being in breach of contract. But please be assured that I was not referrring to you or making any terrible accusations towards you or anyone in particlar, in my brief discussion of prejudice in hiring. I was only saying that we all have at some point in our career observed some unconscious prejudice in action, whether in ourselves or in some-but by no means all of our colleagues in physics. Thanks, Lee Jacques,

“The strongest possible form of background independence consistent with quantum gravity in asymptotically anti-de Sitter spacetimes.” according to you, does not satisfy the standard definition of background independence (or in Greene’s terms, manifest background independence) which is that no classical metric and no global symmetries are required to state the laws of the theory. But it does satisfy something weaker than that and because I respect the facts I have been careful in speaking and writing to state clearly the situation. I don’t argue from my feelings, when there is a clear logical case for something I acknowledge it and try to state it clearly. It seems like the pay back I get for trying to be accurate about the facts and precise in my characterization of them is to get insulted and slammed by people who deliberately twist a subtle distinction to make it look like a contradiction. I am still waiting for someone to acknowledge that they had the impression that I did not mention in the book that the Maldacena conjecture could satisfy some (any!) form of background independence, and that, having read the quote from the book, they recognize that impression was wrong. I would like to get some recognition of the fact that on many issues, including this one, my book describes the factually correct situation.

Dear Mark,

I accept your apology, I hope you can accept mine. In fact, one cannot walk away from a contract signed years earlier a few weeks before publication over a dispute over advertising copy, without being in breach of contract. But please be assured that I was not referrring to you or making any terrible accusations towards you or anyone in particlar, in my brief discussion of prejudice in hiring. I was only saying that we all have at some point in our career observed some unconscious prejudice in action, whether in ourselves or in some-but by no means all of our colleagues in physics.

Thanks,

Lee

]]> By: Clifford http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3056 Clifford Tue, 31 Oct 2006 23:43:03 +0000 http://asymptotia.com/2006/10/27/more-scenes-from-the-storm-in-a-teacup-v/#comment-3056 TheGraduate:- What did he do to make sure it was accurate? He made something up about me, something I was supposed to have done....and then put it on his blog. Is that his best!? That's utterly ridiculous. And certainly not reasonable, I hope you agree. -cvj TheGraduate:- What did he do to make sure it was accurate? He made something up about me, something I was supposed to have done….and then put it on his blog. Is that his best!? That’s utterly ridiculous. And certainly not reasonable, I hope you agree.

-cvj

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