Non-minimal Higgs content in standard-like models from D-branes at a ZN singularity

We show that attempts to construct the Standard Model, or the MSSM, by placing D3-branes and D7-branes at a Z(N) orbifold or orientifold singularity all require that the electroweak Higgs content is non-minimal. For the orbifold the lower bound on the number n (H) + n ((H) over bar) of electroweak Higgs doublets is the number n (q(L)(c)) = 6 of quark singlets, and for the orientifold the lower bound can be one less. As a consequence there is a generic flavour changing neutral current problem in such models. (C) 2004 Published by Elsevier B.V.