Limits of the D-brane action

Abstract

For background geometries whose metric contain a scale $\gamma$ we reformulate the Born-Infeld D-brane action in terms of $\epsilon \equiv \gamma /(2\pi \alpha ')$. This may be taken as a starting point for various perturbative treatments of the theory. We study two limits that arise at zeroth order of such perturbations. In the first limit, that corresponds to the $g_s\to\infty$ with $\epsilon$ fix, we find a "string parton" picture, also in the presense of some background RR-fields. In the second limit, $\epsilon\to 0$, we find a topological model.Comment: 13 pages, Latex. Minor errors are corrected. To appear in JHE