String theory derivation of RR couplings to D-branes

Abstract

We derive the couplings of D-branes to the RR fields from the first principles, i.e. from the nonlinear sigma-model. We suggest a procedure to extract poles from string amplitudes, before the eventual formula for the couplings is obtained. Using the fact that the parts of amplitudes with poles are irrelevant for the effective action this procedure ultimately simplify the derivation since it allows us to omit these poles already from the very beginning. We also use the vertex for the RR fields in the (-3/2,-1/2) ghost picture as the useful tool for the calculation of such string amplitudes. We carry out the calculations in all orders of brane massless excitations and obtain the Myers-Chern-Simons action. Our goal is to present the calculations in full technical details and specify the approximation in which one obtains the action in question.