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My question about string theory

  1. Jan 20, 2008 #1
    First of all, I dont know anything about mathematical physics whatsoever. Im not well aquainted with it. So please forgive me if im misinterpretating something.

    My question has to do with MOND and TeVeS. If this theory happen to be true and Gravity is different or incosistant in huge places of the universes, then could the math that was used to get string theory be wrong as a theory of everything, or still String theory is consistent with MOND and TeVeS?

    thanks in advance
  2. jcsd
  3. Jan 21, 2008 #2


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    So far string research has failed to produce a theory of everything, and it is in decline.
    String-ish mathematics can be made consistent with pretty much anything---there is no one unique "string theory".

    David Gross is probably the most influential string theorist (Edward Witten has gotten out of string) and the only one to have won the Nobel (for some non-string work he did). He has said repeatedly "We don't know what string theory is."

    What that refers to is the earlier hope that something called M-theory would be found which would put various forms of stringery together in one package. But no M-theory has been found. No main M-theory equation, no fundamental principle analogous to Einstein's equivalence principle. No string/M theory exists. Instead, so far there is a bunch of indefinite ideas and some interesting mathematical techniques.

    Consequently, the rate of publication of stringy papers has been declining since about 2002. More important: the rate of CITATION of string papers has declined as well----string theorists now find the recent papers by other string theorists papers less significant and cite them less in their own research.

    As the field has declined, good people (like Witten) have simply gotten out and found other things to do research in.
    A twentypercent cut in faculty jobs is planned for string theorists over the next four years according to a government advisory panel HEPAP that made a survey of the physics departments of US universities. At the same time (June 2007) HEPAP reported a planned 20 percent increase in faculty specializing in astrophysics. Smaller changed in other areas.

    So the real world is gradually adapting to the perceived failure and decline of string to produce a theory. Note that string research could still succeed in coming up with a clear unique testable theory consistent with past observation and predicting new phenomena that established theories don't so it could be tested.
    Even with a 20 percent cut in jobs, or even 50 percent, there would still be a huge crowd of people working in the field and they might come up with something. David Gross says some totally new ideas are needed and they might be found.

    But there are newer pathways to unification to explore, and interesting newer approaches to unifying quantum theory with General Relativity which have been making visible progress. So the picture is changing.



    String thinking is basically irrelevant to MOND and TeVeS. String is amorphous and nonpredictive. There are a huge number of variations most of which have a hard time predicting even known stuff like the Standard Particle Model. So the question needs to be generalized to include other approaches to fundamental physics and quantum gravity.

    What you are asking is very interesting, if you generalize it and bring it up to date.

    As you know, MOND and TeVeS are pretty much dead as ideas now because people are IMAGING AND MAPPING DARK MATTER and MOND was invented to explain rotation curves without dark matter. But now we see clouds of dark matter by weak lensing and study their flow around in clusters and superclusters. We see how they behave in collisions etc.

    So if you watch the publication rates there has been a drop-off in publication of research papers in the general MOND area.

    However people are coming up with exciting new ways to explain the DARK ENERGY effect. There are some really interesting new papers explaining acceleration in expansion without requiring any exotic matter----no hypothetical dark energy field needed!

    Also several recent research papers that I've seen have derived the value of the cosmological constant from more basic considerations.

    This work is too speculative to put much faith in, at this point, but it is a lively research area with a ferment of new ideas. It is also connected to some newer approaches to quantum gravity. Names to recall in this connection are Reuter, Aldrovandi, Wiltshire, Percacci, Pereira, Loll, Smolin---I'm probably forgetting half of those I should mention, and this is in no particular order.

    I think TeVeS and MOND are dead. But there are OTHER modifications of gravity that have appeared in the past couple of years----some of which explain the cosmological constant---i.e. 'dark energy'. And Dark Energy research is getting BIG. The government agencies have been persuaded to commit really substantial support to search for and study of. This could help keep string researchers on the pay-roll.

    Even though string research has gotten a bit old and is in decline, there are still a lot of people working in it! String could get into the news in the next few years by coming up with ideas of what might constitute Dark Energy, or what might be causing the observed effect. So the driving interest in Dark Energy could serve to feed and revitalize string-talk.

    However help to string is not likely to come by way of TeVeS. As i say they are kind of irrelevant to each other----string being too amorphous and TeVeS being dead.

    these are just my personal views, H.M.Murdock, and hopefully other people will present you with different opinions :biggrin:
    Last edited: Jan 21, 2008
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