Pseudo-anomalous U(1) symmetry in the strong coupling limit of the heterotic string

We discuss, in the context of the strongly-coupled E-8 x E-8 heterotic stri ng proposed by Horava and Witten, the appearance of anomalous U(1)(X) symme tries of a nonperturbative origin, related to the presence, after compactif ication, of five-branes in the five-dimensional bulk of the theory. We comp ute the gauge anomalies and the induced Fayet-Iliopoulos terms on each boun dary, which we find to be lower than the universal one induced in the weakl y coupled case. (C) 1998 Published by Elsevier Science B.V. All rights rese rved.