Is String Theory the Key to Understanding the Multiverse?

[hossi]

"[URL Theory - From Physics to Metaphysics
Authors: Reiner Hedrich
http://xxx.lanl.gov/abs/physics/0604171

Currently, string theory represents the only advanced approach to a unification of all interactions, including gravity. In spite of the more than thirty years of its existence it did not make any empirically testable predictions. And it is completely unknown which physically interpretable principles could form the basis of string theory. At the moment, "string theory" is no theory at all, but rather a labyrinthic structure of mathematical procedures and intuitions which get their justification from the fact that they, at least formally, reproduce general relativity and the standard model of elementary particle physics as low energy approximations. However, there are now strong indications that string theory does not only reproduce the dynamics and symmetries of our standard model, but a plethora of different scenarios with different low energy nomologies and symmetries. String theory seems to describe not only our world, but an immense landscape of possible worlds. So far, all attempts to find a selection principle which could be motivated intratheoretically remained without success. So, recently the idea that the low energy nomology of our world, and therefore also the observable phenomenology, could be the result of an anthropic selection from a vast arena of nomologically different scenarios entered string theory. Although multiverse scenarios and anthropic selection are not only motivated by string theory, but lead also to a possible explanation for the fine tuning of the universe, they are concepts which transcend the framework defined by the epistemological and methodological rules which conventionally form the basis of physics as an empirical science.

 

[hossi]

Anybody read that? The author makes quite extreme use of footnotes. E.g. page 3 is completely covered by footnotes! Can someone make sense out of point iii)

iii) Black Holes exist as the product of gravitational collapse, but they do not exert any effects on their environment. This is the craziest of all scenarios

Indeed, it seems to me pretty crazy.


B.

 

[hossi]

Me again. I just read THE END. Here is it:

The simple reason is that once a non-falsifiable theory is preferred to falsifiable alternatives, the process of science stops amd further increases in knowledge are ruled out.~Smolin (2004)

So, are there alternatives to anthropic reasoning with regard to the selection of scenarios from the string landscape, ot to the string landscape itself, or even to string theory? Or is this simply the end?

How DRAMATIC! What is all that talk about the END of physics and the CRISIS of physics and the TROUBLE in physics? Sorry, I can't avoid thinking, if there was less blah and more action, there would be no crisis.

A little less conversation, a little more action please~Elvis

 

[marcus]

Anybody read that?...

at that place in the paper he is arguing that there is a serious need for a QG, or a general relativistic quantum physics.

some people dismiss the need for QG and say that there is no problem because GR is a good theory in its domain of applicability and
QM also is a good theory where it applies. so why worry.

Don't misunderstand me. I don't say this. But Hedrich is being very meticulous and he wants to cover every part of the argument. So he answers those people.

He says look, there IS a gap. Look at BHs.

then he employs the philosophers form of argument REDUCTIO AD ABSURDUM.

he says we have no unified theory to model how a charged black hole interacts with the environment
[maybe he is wrong, maybe physicists DO have an adequate theory, but he is trying to show that there is a GAP at the BH horizon where people just patch together some QM ideas or QED ideas with some GR ideas and basically just FAKE it. so his footnote is intended to show this bastard cobbling together of two incompatible theories, this patchwork stuff is absurd and doesn't work]

I don't know if Hawking proof of BH hawking radiation is actually rigorous, do you? I think it is "semiclassical"----a provisional ad hoc mixture of GR and QED reasoning. I merely THINK this, you can tell me for sure if that is right.

Anyway he does not take his "scenario 3" seriously. he is just trying to show that all possibilities using present existing theories are absurd.
he wants to prove to the educated nonphysics layman that some QG combining QM and GR is needed to deal with some definite problems.Remember that the Hedrich paper is for non-specialists. It is more for an intelligent politician or administrator if any exist, or a philosopher of science----it is not (I think) aimed at physicists. Would you agree?

 

[hossi]

Anyway he does not take his "scenario 3" seriously. he is just trying to show that all possibilities using present existing theories are absurd.
he wants to prove to the educated nonphysics layman that some QG combining QM and GR is needed to deal with some definite problems.


Remember that the Hedrich paper is for non-specialists. It is more for an intelligent politician or administrator if any exist, or a philosopher of science----it is not (I think) aimed at physicists. Would you agree?

I hope he doesn't take the scenario seriously, but esp. for the non-specialist I think he doesn't make that very clear. I don't think iii) would survive confrontation with facts we know about astrophysics and GR.

B.

 

[marcus]

Some background on Reiner Hedrich, in case anyone's interested

Back in January the German periodical Die Zeit had an article about Hedrich and others called “Die Physik steckt in der Krise”

Reiner Hedrich was funded by the German Science Foundation to study the situation in theoretical physics, and he was interviewed for the article in Die Zeit.

A scientist blogger Eli Rabett provided this translation of the Zeit article:
http://rabett.blogspot.com/2006/01/lost-this-is-something-of-new.html

It gives reasons why the Funding Agencies like the German Science Foundation might think that theoretical physics was screwing up, and got on the wrong track with superstring, and that simply throwing money at the string theorists might not solve the problem. So they gave Hedrich a GRANT to study the situation. So far sounds pretty normal and typical.

So Hedrich has to describe the situation and, if possible, give the establishment people some policy-advice.

I think this article you mentioned, Sabine, is (at least in part) like a report from his oversight study that the Foundation paid him to do:

http://arxiv.org/abs/physics/0604171
String Theory - From Physics to Metaphysics

There was some discussion of Hedrich at Woit's blog
A German physicist named Andre Bresges seemed to vouch for him and gave a bit of background on Hedrich and the author, Max Rauner, of the article in Die Zeit who interviewed Hedrich:
http://www.math.columbia.edu/~woit/wordpress/?p=334
http://www.math.columbia.edu/~woit/wordpress/?p=334#comment-8199

 

[hossi]

Some background on Reiner Hedrich, in case anyone's interested

Back in January the German periodical Die Zeit had an article about Hedrich and others called “Die Physik steckt in der Krise”

Thanks marcus! That's indeed interesting. I remember a friend sent that article to me, and I found it quite funny that the DFG payed someone to clarify what the fu*k the theoretical physicists are doing

The article from Max Rauner however (which came with the interview), I found a bit disturbing. Rauner manages to mention the many worlds theory toghether with intelligent design and the string landscape, throws in some 'quotations' by Smolin (I doubt Lee ever said that), and tries to be ironic about the physicist's struggle to constructive criticism. Okay, I am not being objective, but for a theoretical physicist I found the article a bit insulting. Not to mention, that I don't like all that talking about the so-called crisis.

Here is the link, (its in German)

http://www.zeit.de/2006/05/Kosmologie?page=3"
(try http://babelfish.altavista.com/babelfish/trurl_pagecontent?lp=de_en&url=http%3A%2F%2Fwww.zeit.de%2F2006%2F05%2FKosmologie%3Fpage%3Dall" )

Solche nicht überprüfbaren Theorien treiben dem Physiker Lee Smolin den kalten Schweiß auf die Stirn. Wenn die Physik das Prinzip der Überprüfbarkeit aufgebe, so warnt Smolin, gerate sie in die Nähe religiöser Theorien wie etwa der Schöpfungslehre vom Intelligent Design. »Die Gefahr liegt direkt vor unserer Haustür«, sagt Smolin. Der katholischen Kirche wiederum ist die Viele-Welten-Theorie nicht religionskompatibel genug. So geißelte der Wiener Kardinal Christoph Schönborn bei seinem viel beachteten Angriff auf die Evolutionstheorie I am vergangenen Jahr explizit auch die Hypothese vom Multiversum. Sie widerspreche den überwältigenden Belegen für Zweck und Design der Natur.

 

[bonjour]

String theory works on the basis of acceptance that gravity is a force correct?

(e2a: or that forces exist?)

 

[marcus]

String theory works on the basis of acceptance that gravity is a force correct?
...

Bonjour, your question should be answered, but before I or anyone else tries to answer, I think we should update the research references.
Reiner Hedrich has given an overview of the status and problems of both string and non-string QG.

Besides the August 2006 paper which Bee Hossenfelder referred to there is this October 2006 paper:
http://arXiv.org/abs/physics/0610168
The Internal and External Problems of String Theory - A Philosophical View
Reiner Hedrich
J.Gen.Phil.Sci.38:261-278,2007
(Submitted on 21 Oct 2006)
"String theory is at the moment the only advanced approach to a unification of all interactions, including gravity. But, in spite of the more than thirty years of its existence, it does not make any empirically testable predictions, and it is completely unknown which physically interpretable principles could form the basis of string theory. At the moment, 'string theory' is no theory at all, but rather a labyrinthic structure of mathematical procedures and intuitions. The only motivations for string theory consist in the mutual incompatibility of the standard model of quantum field theory and of general relativity as well as in the metaphysics of the unification program of physics, aimed at a final unified theory of all interactions, including gravity. The article gives a perspective on the problems leading to and resulting from this situation."

And more recently there are two Hedrich papers that appeared in 2009:

http://arXiv.org/abs/0902.0190
Quantum Gravity: Has Spacetime Quantum Properties?
Reiner Hedrich
31 pages
(Submitted on 2 Feb 2009)
"The incompatibility between GR and QM is generally seen as a sufficient motivation for the development of a theory of Quantum Gravity. If - so a typical argumentation - QM gives a universally valid basis for the description of all natural systems, then the gravitational field should have quantum properties. Together with the arguments against semi-classical theories of gravity, this leads to a strategy which takes a quantization of GR as the natural avenue to Quantum Gravity. And a quantization of the gravitational field would in some sense correspond to a quantization of geometry. Spacetime would have quantum properties. But, this strategy will only be successful, if gravity is a fundamental interaction. - What, if gravity is instead an intrinsically classical phenomenon? Then, if QM is nevertheless fundamentally valid, gravity can not be a fundamental interaction. An intrinsically classical gravity in a quantum world would have to be an emergent, induced or residual, macroscopic effect, caused by other interactions. The gravitational field (as well as spacetime) would not have any quantum properties. A quantization of GR would lead to artifacts without any relation to nature. The serious problems of all approaches to Quantum Gravity that start from a direct quantization of GR or try to capture the quantum properties of gravity in form of a 'graviton' dynamics - together with the, meanwhile, rich spectrum of approaches to an emergent gravity and/or spacetime - make this latter option more and more interesting for the development of a theory of Quantum Gravity. The most advanced emergent gravity (and spacetime) scenarios are of an information-theoretical, quantum-computational type."


http://arXiv.org/abs/0908.0355
Quantum Gravity: Motivations and Alternatives
Reiner Hedrich
32 pages
(Submitted on 3 Aug 2009)


Bonjour, it seems to me that Hedrich is no longer so interested in making critique of string theory, perhaps he sees it declining in importance, or he has said already all he wants to say. It seems to me that now he is turning his attention to a critique of non-string quantum gravity. I have so far only seen the abstracts of the two papers of 2009. I hope we can learn something from them. If you want to take a look, just use the link to the abstract which I gave, and then click on "PDF". The articles can be freely downloaded.
I hope someone will comment, in case there is something useful here.

 

[bonjour]

Much appreciated Marcus. Many many thanks to you.