ON THE STRONGLY COUPLED HETEROTIC STRING

We analyze in detail the anomaly cancellation conditions for the stron gly coupled E-8 x E-8 heterotic string introduced by Horava and Witten and find new features compared to the ten-dimensional Green-Schwarz m echanism. We project onto ten dimensions the corresponding Lagrangian of the zero-mode fields. We find that it has a simple interpretation p rovided by the conjectured heterotic string/fivebrane duality. The par t which originates from eleven-dimensions is naturally described in fi vebrane language. We discuss physical couplings and scales in four dim ensions. (C) 1997 Published by Elsevier Science B.V.