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High Energy Physics - Theory, hep-th
Abstract:
We present a recursive method to calculate the $\alpha'$-expansion of disk
integrals arising in tree-level scattering of open strings which resembles the
approach of Berends and Giele to gluon amplitudes. Following an earlier
interpretation of disk integrals as doubly partial amplitudes of an effective
theory of scalars dubbed as $Z$-theory, we pinpoint the equation of motion of
$Z$-theory from the Berends-Giele recursion for its tree amplitudes. A computer
implementation of this method including explicit results for the recursion up
to order $\alpha'^7$ is made available on the website
http://repo.or.cz/BGap.git
