Supersymmetry breaking in the observable sector of superstring models

We discuss the communication of supersymmetry breaking from the gravitino mass m 3 2 to gaugino masses m 1 2, scalar masses m0, and trilinear scalar couplings A in superstring models, assuming that the effective low-energy N=1, d=4 supergravity has a modified "no-scale" structure. It is known that m 1 2 ≠ 0 at the one-loop level, whilst squared scalar masses m02 van at the one-loop level. We analyse a large class of two-loop diagrams, showing that their quadratic divergences cancel and that they contribute m20=O4(m 3 2/m2P). We also show that A appears in one-loop order, but is much smaller than m 1 2. Therefore the initial conditions m 1 2≫A ≫m0 are appropriately in renormalization group analyses of effective low-energy models inspired by the superstring. © 1987.