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 \times E_8 heterotic string proposed by Horava 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. 
P.Binetruy, C.Deffayet, E.Dudas, P.Ramond