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

We discuss, in the context of the strongly-coupled E8×E8 heterotic string proposed by Hor̆ava and Witten, the appearance of anomalous U(1)X symmetries of a nonperturbative origin, related to the presence, after compactification, of five-branes in the five-dimensional bulk of the theory. We compute the gauge anomalies and the induced Fayet–Iliopoulos terms on each boundary, which we find to be lower than the universal one induced in the weakly coupled case.