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String theory is a complete scientific failure by Daniel Friedan

by bananan
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Haelfix
#19
Oct28-06, 01:00 PM
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Why don't people work on string field theory as much as they used too. It seemed the most natural and elegant formulation yet devised (and of course BI). Were the technical problems too hard to overcome?
selfAdjoint
#20
Oct28-06, 01:25 PM
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Quote Quote by Haelfix
Why don't people work on string field theory as much as they used too. It seemed the most natural and elegant formulation yet devised (and of course BI). Were the technical problems too hard to overcome?
I am just guessing here, but it seems to me that regular string theory has become so rich and mathematically interconnected that their are a lot of opportunities to do satisfying research and discovery that are open to hard work and a modicum of talent. And as I've been looking at string field papers on the arxiv for the last few years, SFT doen't. It's still at the major breakthrough stage where Sen's and Witten's work still sits out there and the ambitious post doc can't find any quick and handy hooks to push forward with.
R.X.
#21
Oct28-06, 05:09 PM
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Quote Quote by selfAdjoint
I am just guessing here, but it seems to me that regular string theory has become so rich and mathematically interconnected that their are a lot of opportunities to do satisfying research and discovery that are open to hard work and a modicum of talent. And as I've been looking at string field papers on the arxiv for the last few years, SFT doen't. It's still at the major breakthrough stage where Sen's and Witten's work still sits out there and the ambitious post doc can't find any quick and handy hooks to push forward with.
Pretty good characterization. Indeed closed string field theory has turned out to be extremely complex (non-polynomial), and while open strings are much simpler, it nevertheless seems hard to make progress towards a useful background independent formulation, using traditional methods. Probably a quite different way of thinking is needed.

An interesting toy model was discussed by Witten a while ago (hep-th/9306122), and its ideology has been revived more recently (eg in hep-th/0412139, hep-th/0502211). In the latter an attempt was made to construct a wavefunction over the (moduli) space of compactifications, and morally speaking, this is what one wants to have: some measure for distinguishing between different background geometries, eg via the peaking of a wave function. All this seems in early stages, though.

Quote Quote by selfAdjoint
... and the ambitious post doc can't find any quick and handy hooks to push forward with.
While this is generally true for a complicated subject, there indeed _are_ ambitious young postdocs who, just by themselves, _can_ make a major breakthrough, in a subject that has stalled since quite a while, see eg hep-th/0511286.
selfAdjoint
#22
Oct28-06, 08:06 PM
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Wow R.X.! That Schnabl paper looks fascinating! An analytic solution of the non-perturbative tachyon vacuum of Witten's three-vertex model.

Analytic solution for tachyon condensation
in open string field theory
Martin Schnabl

Department of Physics, Theory Division,
CERN, CH-1211, Geneva 23, Switzerland
E-mail: martin.schnabl@cern.ch
Abstract
We propose a new basis in Witten’s open string field theory, in which the star product simplifies considerably. For a convenient choice of gauge the classical string field equation of motion yields straightforwardly an exact analytic solution that represents the nonperturbative tachyon vacuum. The solution is given in terms of Bernoulli numbers and the equation of motion can be viewed as novel Euler–Ramanujan-type identity. It turns out that the solution is the Euler–Maclaurin asymptotic expansion of a sum over wedge states with certain insertions. This new form is fully regular from the point of view of level truncation. By computing the energy
difference between the perturbative and nonperturbative vacua, we prove analytically Sen’s first conjecture.
Has there been any followup on this work?
marcus
#23
Oct28-06, 09:53 PM
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Quote Quote by selfAdjoint
Has there been any followup on this work?
Perhaps you can find some followup here
http://arxiv.org/cits/hep-th/0511286
This is arxiv's list of 14 papers which have appeared subsequently and which have cited Martin Schnabl's November 2005 paper
http://arxiv.org/abs/hep-th/0511286
It is not bad for the first year---citations include some by well-known people: Douglas, Kachru, Trivedi, Washington Taylor, Zwiebach,...
selfAdjoint
#24
Oct29-06, 07:34 AM
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Thanks for the list Marcos. I know I can always go to you for bibliographical help!

On the list these two papers seem to show that Schnabl's result is robust:

hep-th/0603195
From: Fuchs Ehud [view email]
Date (v1): Fri, 24 Mar 2006 20:09:12 GMT (9kb)
Date (revised v2): Tue, 4 Apr 2006 18:20:49 GMT (9kb)
On the validity of the solution of string field theory
Authors: Ehud Fuchs, Michael Kroyter
Comments: JHEP style, 9+1 pages. Typos corrected
Report-no: AEI-2006-017
Journal-ref: JHEP 0605 (2006) 006
DOI: 10.1088/1126-6708/2006/05/006
We analyze the realm of validity of the recently found tachyon solution of cubic string field theory. We find that the equation of motion holds in a non trivial way when this solution is contracted with itself. This calculation is needed to conclude the proof of Sen's first conjecture. We also find that the equation of motion holds when the tachyon or gauge solutions are contracted among themselves.
hep-th/0603159
From: Yuji Okawa [view email]
Date (v1): Tue, 21 Mar 2006 20:01:02 GMT (28kb)
Date (revised v2): Fri, 28 Apr 2006 17:37:54 GMT (28kb)
Comments on Schnabl's analytic solution for tachyon condensation in Witten's open string field theory
Authors: Yuji Okawa (MIT)
Comments: 33 pages, 4 figures, LaTeX2e; v2: minor changes, version published in JHEP
Report-no: MIT-CTP-3727
Journal-ref: JHEP 0604 (2006) 055
Schnabl recently constructed an analytic solution for tachyon condensation in Witten's open string field theory. The solution consists of two pieces. Only the first piece is involved in proving that the solution satisfies the equation of motion when contracted with any state in the Fock space. On the other hand, both pieces contribute in evaluating the kinetic term to reproduce the value predicted by Sen's conjecture. We therefore need to understand why the second piece is necessary. We evaluate the cubic term of the string field theory action for Schnabl's solution and use it to show that the second piece is necessary for the equation of motion contracted with the solution itself to be satisfied. We also present the solution in various forms including a pure-gauge configuration and provide simpler proofs that it satisfies the equation of motion.
and Schnabl's own followup (second author with Ian Ellwood ) carries his result onward to prove the third of Sen's famous conjectures. Wonderful stuff!

hep-th/0606142
From: Ian Ellwood [view email]
Date (v1): Thu, 15 Jun 2006 19:06:58 GMT (28kb)
Date (revised v2): Fri, 25 Aug 2006 02:15:47 GMT (28kb)
Proof of vanishing cohomology at the tachyon vacuum
Authors: Ian Ellwood, Martin Schnabl
Comments: 19 pages, 4 figures; v2: references added
We prove Sen's third conjecture that there are no on-shell perturbative excitations of the tachyon vacuum in open bosonic string field theory. The proof relies on the existence of a special state A, which, when acted on by the BRST operator at the tachyon vacuum, gives the identity. While this state was found numerically in Feynman-Siegel gauge, here we give a simple analytic expression.


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