Statistical Mechanics of Multiply Wound D-Branes

The D-brane counting of black hole entropy is commonly understood in terms of excitations carrying fractional charges living on long, multiply-wound branes (e.g. open strings with fractional Kaluza-Klein momentum). This paper addresses why the branes become multiply wound. Since multiply wound branes are T-dual to branes evenly spaced around the compact dimension, this tendency for branes to become multiply wound can be seen as an effective repulsion between branes in the T-dual picture. We also discuss how the fractional charges on multiply wound branes conspire to always form configurations with integer charge.