  Brane world scenarios offer a way of setting the cosmological constant to
zero after supersymmetry breaking provided there is a sufficient number of
adjustable integration constants/parameters. In the case of the Horava-Witten
theory compactified on a Calabi-Yau threefold, we argue that it is difficult to
find enough freedom to get a zero (or small) cosmological constant after
supersymmetry breaking.
