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String backgrounds

  1. Feb 26, 2006 #1
    I can find a string theory background by requiring that the world sheet
    beta-functions vanish, as conformal invariance of the world sheet
    theory is necessary for consistency. This gives me what is called
    background field equations. Or I can just look at low-energy limit of
    strings. So I compute some string scattering amplitudes and look what
    becomes of them in the IR-limit. Then I try to write down a field
    theory Lagrangian which reproduces those low-energy amplitudes. Then
    the Euler-Lagrange equations of that Lagrangian tell me what
    backgrounds I can have.

    Is there a theorem that says that the two different ways of getting
    spacetime field equations must give the same answer in the low-energy
    limit? If the two answers were to differ it would seem to indicate an
    inconsistency, so we don't expect that. On the other hand it could just
    mean that the low-energy method isn't quite "kosher". Do I remember
    well that Michael Douglas complained about the effective field theory
    appraoch to string theory. What was the gist of his argument? Is it
    related to my question? Is it being taken seriously by string theorists
    these days?

  2. jcsd
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