Conditions on supersymmetry soft-breaking terms from GUTs

We study the effect of integrating out the heavy fields in a supersymmetric GUT which does not contain small mass parameters in the limit of exact supersymmetry. The trilinear ($A$) and bilinear ($B$) coefficients of the supersymmetry soft-breaking terms of the low-energy effective theory are related in a simple and model-independent way to those of the underlying theory. {}From these relations, we obtain the bound $|B|\ge 2$, which, together with the requirements of stability of the potential and electroweak symmetry breaking, imposes severe constraints on the space of allowed supersymmetric parameters. In models based on supergravity with a flat K\"ahler metric, we obtain $B=2$, instead of the relation $B=A-1$ usually used in phenomenological applications. The low-energy theory contains also a supersymmetric mass term $\mu$ for the two Higgs doublets, which is of the order of the supersymmetry-breaking scale.