Effectiveness ofD-branes in the description of near-extremal black holes

It is known that weak coupling calculations of absorption or emission by slightly nonextremal $D$-brane configurations are in exact agreement with semiclassical results for the black holes they describe at strong couplings. We investigate one open string loop corrections to processes involving single and parallel $D$-branes and show that a class of relevant terms vanish, indicating that these processes are not renormalized. Our results have implications for five-dimensional black holes and extremal 3-branes.