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Jack Tremarco science forum beginner
Joined: 19 Jun 2005
Posts: 7

Posted: Sat Feb 25, 2006 7:20 pm Post subject:
String backgrounds



I can find a string theory background by requiring that the world sheet
betafunctions 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 lowenergy limit of
strings. So I compute some string scattering amplitudes and look what
becomes of them in the IRlimit. Then I try to write down a field
theory Lagrangian which reproduces those lowenergy amplitudes. Then
the EulerLagrange 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 lowenergy
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 lowenergy 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?
Thanks,
Jack 

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