2005-06-06 15:16:22 UTC
and there is something very basic that
I'm getting badly confused about. We all know
that in string theory there are higher-order
corrections to the Einstein-Hilbert lagrangian
coming both from loops and from alpha' corrections.
Let's think about the alpha' corrections. Normally
people say that these higher-order curvature terms
are "suppressed" by powers of alpha'. My question
is this: in four dimensions, the coefficients would
really be things like alpha'/G, where G is Newton's constant.
This is [L_s/L_p]^2 , where L_s is the string length
scale and L_p is the Planck length. But normally,
if we believe in weakly coupled strings, this is a
*large* number, not a small one! So in what sense
are the string corrections to the EH lagrangian
"suppressed"? I know this has some very simple
answer, somebody please kick me........