Friday, January 20, 2006

Worldsheet genus from membranes

David Berman and Malcolm Perry have studied the question how the power of the coupling constant whose exponent is the Euler character arises from the membrane viewpoint.

Note that in type II (or heterotic E8 x E8) string theory, the string coupling constant is the radius of the 11th dimension (in the 11D Planck units) to the power of 3/2, up to a numerical factor. David and Malcolm obtain the correct factor by a quantum calculation that closely follows the worldsheet picture.

However, they must rescale the "6g-6" moduli of the Riemann surfaces by a factor that nontrivially gives the right power of the coupling constant. I am a bit confused why they only count the "6g-6" bosonic moduli and not the "4g-4" fermionic moduli (if we adopt the RNS formalism; the number is replaced by "2g-2" only in the heterotic case) that could potentially change the power of the coupling constant. But I guess that David and Malcolm would tell us that they must use, for reasons that I don't follow, the Green-Schwarz formalism. However, the only place where the name of Michael Green appears in the paper are the acknowledgements.

In Matrix String Theory, the correct power "3/2" of the radius comes from the dimension of the DVV operator, and the details how this result "3/2" is obtained differs in between heterotic strings and type IIA strings. So I am a bit surprised that David and Malcolm have a universal answer.

At any rate, it is conceivable that David will write an answer to this particular complaint here soon.

Another story: mathematician David Goss has pointed out an interview with his doppelgange(r) who has won the 2004 Nobel p(r)ize, namely David Gross himself.

As you may have heard from Peter Woit, string theorists have learned from the global warming "scientists". Their classic Stephen Schneider has described the necessity of fraud and lies in climate science as follows:
  • ... And like most people we'd like to see the world a better place, which in this context translates into our working to reduce the risk of potentially disastrous climatic change. To do that we need [Scientists should consider stretching the truth] to get some broadbased support, to capture the public's imagination. That, of course, entails getting loads of media coverage. So we have to offer up scary scenarios, make simplified, dramatic statements, and make little mention of any doubts we might have. ...

Because of some recent mis-pronouncement that have been easily mis-interpreted as abused by septics such as Peter Woit, David Gross - who is otherwise a great optimist and a person who can appreciate the work of others - was criticized by the so-called scientific consensus and the central committee of the secret police of string theory. He was forced to give an interview in which he suppresses all doubts about string theory, in agreement with Schneider's principle of balance between the truth and politics. (And the journalist "improved" the interview so that GUT and TOE were treated as synonyma.)

Of course, I am joking - string theory is on the contrary one of the few scientific disciplines where it does NOT work this way. ;-)

At any rate, I am happy that a reader of both Peter Woit's blog as well as mine has discovered that some recent comments about David Gross's attitude to string theory on Peter Woit's blog have been complete crap. It will still take a lot of time before people realize that the rest of Peter Woit's statements about string theory is also bullshit, but there is a lot of time for these developments.

1 comment:

  1. Dear Lumo,

    The simple reason why we did not mention supermoduli is that there aren't any. For the M2-brane, there is only a Green-Schwarz formulation (worked out by Eric Bergshoeff,
    Ergin Sezgin and Paul Townsend and cited by us). In the GS formulation, there is no world volume superpartner of the metric, thus no supermoduli. It is intriguing that there is no (known) analog of the RNS formulation.

    David and Malcolm