HYPERKAHLER MANIFOLDS AND MULTIPLY-INTERSECTING BRANES

This is a summary of the work in the author's recent paper with this t itle written with Jerome Gauntlett, George Papadopoulos and Paul Towns end, hep-th/97022012, We showed hew to construct hyper-Kahler 8-metric s in terms of arrangements of three-dimensional hyperplanes in six-dim ensional euclidean space. The slopes of the planes define two relative ly prime integers (p,g). Under reduction to ten dimensions and T-duali ty we get a geometric picture of the action of SL(2,Z) on the (NS x NS , qR x R) 5-branes of type IIB string theory. Configurations are exhib ited with 3/16'th SUSY.