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Paper IPM / Physic / 8758  


Abstract:  
We have examined the momentum expansion of the disk level Smatrix element of two tachyons and two gauge fields to find, up to onshell ambiguity, the couplings of these fields in the world volume theory of N coincident nonBPS Dbranes to all order of α′. Using the proposal that the action of DbraneantiDbrane is given by the projection of the action of two nonBPS Dbranes with (−1)^{FL}, we find the corresponding couplings in the world volume theory of the braneantibrane system. Using these infinite tower of couplings, we then calculate the massless pole of the scattering amplitude of one RR field, two tachyons and one gauge field in the braneantibrane theory. We find that the massless pole of the field theory amplitude is exactly equal to the massless pole of the disk level Smatrix element of one RR, two tachyons and one gauge field to all order of α′.
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