Black hole dynamics from instanton strings

A D-5-brane bound state with a self-dual field strength on a 4-torus is con sidered. In a particular case this model reproduces the D5-D1 brane bound s tate usually used in the string theory description of 5-dimensional black h oles. In the limit where the brane dynamics decouples from the bulk the Hig gs and Coulomb branches of the theory on the brane decouple. Contrasting wi th the usual instanton moduli space approximation to the problem the Higgs branch describes fundamental excitations of the gauge field on the brane. U pon reduction to two dimensions it is associated with the so-called instant on strings. Using the Dirac-Born-Infeld action for the D-5-brane we determi ne the coupling of these strings to a minimally coupled scalar in the black hole background. The supergravity calculation of the cross section is foun d to agree with the D-brane absorption probability rate calculation. We con sider the near horizon geometry of our black hole and elaborate on the corr esponding duality with the Higgs branch of the gauge theory in the large N limit. A heuristic argument for the scaling of the effective string tension is given.