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The most recent activity in the Smolin/Polchinski discussion was 24 May (a couple of days ago) and again today. It's apt to get buried in the thread of comment at CV, so I will paste it here. Also it's easy to lose track of how many steps there've been in the discussion.
1. Smolin wrote the book, TWP appeared September 2006
2. Polchinski offered a defense of string in a December 2006 "guest" post at CV, rebutting statements made in TWP
http://cosmicvariance.com/2006/12/07/guest-blogger-joe-polchinski-on-the-string-debates/
3. Smolin responded in April 2006, clarifying and emphasizing points of his message here
http://www.thetroublewithphysics.com/Response%20to%20Polchinski.html
and in the comments thread at CV.
http://cosmicvariance.com/2006/12/0...chinski-on-the-string-debates/#comment-257146
http://cosmicvariance.com/2006/12/0...chinski-on-the-string-debates/#comment-257293
4. Polchinski countered with a second, May 2007, guest post at CV
http://cosmicvariance.com/2007/05/21/guest-post-joe-polchinski-on-science-or-sociology/
5. Smolin responded 24-26 May, in the comments to that post.
http://cosmicvariance.com/2007/05/2...inski-on-science-or-sociology/#comment-264869
http://cosmicvariance.com/2007/05/2...inski-on-science-or-sociology/#comment-264955
http://cosmicvariance.com/2007/05/2...inski-on-science-or-sociology/#comment-265385
http://cosmicvariance.com/2007/05/2...inski-on-science-or-sociology/#comment-265876
These are comments #40, 43, 46, and 53 at the CV thread. Of these, the last three are discussion with other posters some of which (like #53) is pretty interesting in its own right and not directly part of the back-and-forth with Polchinski. The one directed to Polchinski is #40, which I will paste here:
============
Lee Smolin on May 24th, 2007 at 2:06 pm
Dear All,
This has come at the worst possible time for me to reflect and reply, so I will not be able to reply quickly and in detail. I thank Joe for the response, there are many points where I would like in time to comment, and others on which we simply have differing scientific judgement. There is nothing wrong with having differing scientific judgements, nor with debating why we take different points of view about open questions. So I thank Joe for taking the time to reply.
It is distressing to however read comments such as the following, “for Smolin to simply dismiss this subject as sociology and groupthink is outrageous.” Anyone who read the book would know that that is not at all what I did. The first 3/4 of the book are straight science and history of science, and the analysis of the strengths and weaknesses of string theory is done there completely on scientific grounds. And there are lots of places where I acknowledge the interest and importance of substantial results about string theory. The assessment of string theory and various claims about it given there is mixed, and balanced. Many successes are mentioned, as are several problems. It is a complex picture, with strong pros and cons, and the open questions are genuinely puzzling. That is why it was worth writing a book, to sort out what to make of it. I am extremely tired of comments which ignore the complexity of the subject and imply also that I ignored it. The useful discussion only starts when someone acknowledges that there are strong reasons for interest in string theory AND also strong reasons to be skeptical that it is the theory of nature.
The discussion of sociology is only in the last of four parts of the book. And there was nothing there that was at all new to people who study the sociology of academics, or experts in general. I am surprised that anyone finds what I wrote surprising.
Joe mentions some standards: “To what extent are known difficulties acknowledged? When a new counterargument is given, is it addressed, and the original assertion modified if necessary? Are facts presented in a clear and direct manner?” I agree these are important standards and I believe I have satisfied them. That is the reason why the assessment of string theory in the book is mixed and balenced. The whole book is the result of such a process, carried out over twenty years of work on and study of the subject, with many discussions with string theorist. Indeed, the book does not contain every argument I made or even published about string theory, precisely because my arguments have been altered by progress in the field as well as improvements in my understanding.
For example Joe mentions here and before my paper with Matthias Arnsdorf on Rehren’s version of AdS/CFT, hep-th/0106073. I would be happy to discuss this, but please first notice that I do not mention the argument of the paper in the book. This is because we realized since posting the paper that there is an important difference between Rehren’s version and Maldecena’s version of AdS/CFT that makes a comparison between them less useful. This has to do with whether the special conformal transformations have anomalies or not. Rehren’s construction is rigorous but because special conformal transformations remain non-anomolous it does not apply to the context of Maldacena’s conjecture.
One way to acknowledge difficiculties in arguments is not to trouble people with them again. So I wish you had noticed that the argument of that paper was not part of the book, and not made an issue of it.
Further, in a few cases, such as the study of heavy ion collisions with AdS/CFT I have acknowledged that important things have happened since the book was finished.
At the same time, it is also necessary that I discuss the extent to which these new results change the overall assessment of the promise of string theory to resolve the 5 major problems I gave in the book. And, for reasons I explained earlier they do not very much. This is because having a phenomenological model of QCD at high temperatures is not one of the five big problems that my book is about. I only discuss string theory there as a candidate for an answer to those questions, and if it happens that some aspects of string theory can help with another question that’s great-we are in the midst here of a very interesting workshop about that. But it does not obviously change the assessment of string theory in relation to the 5 big questions.
My book was concerned only with our progress towards answering those 5 big questions. Most of physics is outside of that. If part of string theory is relevant to heavy ion collisions, wonderful, well worth working on. But I have heard no logical argument that this increases the likelihood that it is the fundamental theory of nature. Newtonian physics has many applications but it is not the theory of nature.
Out of everything else, let me just quickly respond to one assertion:
“I have recently attended a number of talks by leading workers in LQG, at a KITP workshop and the April APS meeting. I am quite certain that the standard of rigor was not higher than in string theory or other areas of physics. In fact, there were quite a number of uncontrolled approximations. This is not necessarily bad - I will also use such approximations when this is all that is available - but it is not rigor.”
This does not acknowledge that in any subject the level of rigor is mixed. If you hear a talk by me you get a presentation of work with much less rigor than in a talk by Thomas Thiemann. In string theory as in other subjects there is a range of rigour.
I made no claim that the subject of LQG has a uniformly higher level of rigor that string theory. I did claim that there are a collection of rigorous results proved by mathemtical physicists, and that they include existence and uniqueness theorems which anchor the foundations of the subject. This is important, first because it does put the subject of LQG on rigorous foundations, second because it refutes the impression that it is useless to require the presence rigorous results in justifying an approach to quantum gtravity.
Thanks,
Lee
================
1. Smolin wrote the book, TWP appeared September 2006
2. Polchinski offered a defense of string in a December 2006 "guest" post at CV, rebutting statements made in TWP
http://cosmicvariance.com/2006/12/07/guest-blogger-joe-polchinski-on-the-string-debates/
3. Smolin responded in April 2006, clarifying and emphasizing points of his message here
http://www.thetroublewithphysics.com/Response%20to%20Polchinski.html
and in the comments thread at CV.
http://cosmicvariance.com/2006/12/0...chinski-on-the-string-debates/#comment-257146
http://cosmicvariance.com/2006/12/0...chinski-on-the-string-debates/#comment-257293
4. Polchinski countered with a second, May 2007, guest post at CV
http://cosmicvariance.com/2007/05/21/guest-post-joe-polchinski-on-science-or-sociology/
5. Smolin responded 24-26 May, in the comments to that post.
http://cosmicvariance.com/2007/05/2...inski-on-science-or-sociology/#comment-264869
http://cosmicvariance.com/2007/05/2...inski-on-science-or-sociology/#comment-264955
http://cosmicvariance.com/2007/05/2...inski-on-science-or-sociology/#comment-265385
http://cosmicvariance.com/2007/05/2...inski-on-science-or-sociology/#comment-265876
These are comments #40, 43, 46, and 53 at the CV thread. Of these, the last three are discussion with other posters some of which (like #53) is pretty interesting in its own right and not directly part of the back-and-forth with Polchinski. The one directed to Polchinski is #40, which I will paste here:
============
Lee Smolin on May 24th, 2007 at 2:06 pm
Dear All,
This has come at the worst possible time for me to reflect and reply, so I will not be able to reply quickly and in detail. I thank Joe for the response, there are many points where I would like in time to comment, and others on which we simply have differing scientific judgement. There is nothing wrong with having differing scientific judgements, nor with debating why we take different points of view about open questions. So I thank Joe for taking the time to reply.
It is distressing to however read comments such as the following, “for Smolin to simply dismiss this subject as sociology and groupthink is outrageous.” Anyone who read the book would know that that is not at all what I did. The first 3/4 of the book are straight science and history of science, and the analysis of the strengths and weaknesses of string theory is done there completely on scientific grounds. And there are lots of places where I acknowledge the interest and importance of substantial results about string theory. The assessment of string theory and various claims about it given there is mixed, and balanced. Many successes are mentioned, as are several problems. It is a complex picture, with strong pros and cons, and the open questions are genuinely puzzling. That is why it was worth writing a book, to sort out what to make of it. I am extremely tired of comments which ignore the complexity of the subject and imply also that I ignored it. The useful discussion only starts when someone acknowledges that there are strong reasons for interest in string theory AND also strong reasons to be skeptical that it is the theory of nature.
The discussion of sociology is only in the last of four parts of the book. And there was nothing there that was at all new to people who study the sociology of academics, or experts in general. I am surprised that anyone finds what I wrote surprising.
Joe mentions some standards: “To what extent are known difficulties acknowledged? When a new counterargument is given, is it addressed, and the original assertion modified if necessary? Are facts presented in a clear and direct manner?” I agree these are important standards and I believe I have satisfied them. That is the reason why the assessment of string theory in the book is mixed and balenced. The whole book is the result of such a process, carried out over twenty years of work on and study of the subject, with many discussions with string theorist. Indeed, the book does not contain every argument I made or even published about string theory, precisely because my arguments have been altered by progress in the field as well as improvements in my understanding.
For example Joe mentions here and before my paper with Matthias Arnsdorf on Rehren’s version of AdS/CFT, hep-th/0106073. I would be happy to discuss this, but please first notice that I do not mention the argument of the paper in the book. This is because we realized since posting the paper that there is an important difference between Rehren’s version and Maldecena’s version of AdS/CFT that makes a comparison between them less useful. This has to do with whether the special conformal transformations have anomalies or not. Rehren’s construction is rigorous but because special conformal transformations remain non-anomolous it does not apply to the context of Maldacena’s conjecture.
One way to acknowledge difficiculties in arguments is not to trouble people with them again. So I wish you had noticed that the argument of that paper was not part of the book, and not made an issue of it.
Further, in a few cases, such as the study of heavy ion collisions with AdS/CFT I have acknowledged that important things have happened since the book was finished.
At the same time, it is also necessary that I discuss the extent to which these new results change the overall assessment of the promise of string theory to resolve the 5 major problems I gave in the book. And, for reasons I explained earlier they do not very much. This is because having a phenomenological model of QCD at high temperatures is not one of the five big problems that my book is about. I only discuss string theory there as a candidate for an answer to those questions, and if it happens that some aspects of string theory can help with another question that’s great-we are in the midst here of a very interesting workshop about that. But it does not obviously change the assessment of string theory in relation to the 5 big questions.
My book was concerned only with our progress towards answering those 5 big questions. Most of physics is outside of that. If part of string theory is relevant to heavy ion collisions, wonderful, well worth working on. But I have heard no logical argument that this increases the likelihood that it is the fundamental theory of nature. Newtonian physics has many applications but it is not the theory of nature.
Out of everything else, let me just quickly respond to one assertion:
“I have recently attended a number of talks by leading workers in LQG, at a KITP workshop and the April APS meeting. I am quite certain that the standard of rigor was not higher than in string theory or other areas of physics. In fact, there were quite a number of uncontrolled approximations. This is not necessarily bad - I will also use such approximations when this is all that is available - but it is not rigor.”
This does not acknowledge that in any subject the level of rigor is mixed. If you hear a talk by me you get a presentation of work with much less rigor than in a talk by Thomas Thiemann. In string theory as in other subjects there is a range of rigour.
I made no claim that the subject of LQG has a uniformly higher level of rigor that string theory. I did claim that there are a collection of rigorous results proved by mathemtical physicists, and that they include existence and uniqueness theorems which anchor the foundations of the subject. This is important, first because it does put the subject of LQG on rigorous foundations, second because it refutes the impression that it is useless to require the presence rigorous results in justifying an approach to quantum gtravity.
Thanks,
Lee
================
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