Membranes from five-branes and fundamental strings from Dp-branes

We argue that the M2-brane is realized as a topological soliton on a coinci dent pair of M5- and anti-M5-branes, as the two five-branes annihilate each other. The topology and quantum numbers of this world-volume soliton are d iscussed in some detail, and its formation is explained qualitatively. It f ollows from a compactification that a D4-anti-D4 pair annihilate and produc e type II fundamental strings. The phenomenon is best described as the conf inement of a world-volume U(1) gauge held on D4-anti-D4, where the confined electric flux string is identified as the fundamental string. This general izes to other Dp-anti-Dp systems, and solves a puzzle recently pointed out by Witten. (C) 1999 Elsevier Science B.V. All rights reserved.