Millimetre-range forces in superstring theories with weak-scale compactification

We show that theories in which supersymmetry is broken via Scherk-Schwarz compactification at the weak scale possess at least one scalar particle with Compton wavelength in the millimetre range, which mediates a force with strength 1/3 of gravity. Such forces are going to be explored in upcoming experiments using micro-electromechanical systems or cantilever technology. We also present a simple way of understanding some decoupling aspects of these theories by analogy with finite-temperature field theory. (C) 1998 Elsevier Science B.V.