Large CP Phases and the Cancellation Mechanism in EDMs in SUSY, String and Brane Models

We show that EDMs obey a simple approximate scaling under the transformation $m_0\to \lambda m_0,m_{{1/2}}\to \lambda m_{{1/2}}$ in the large $\mu$ region when $\mu$ itself obeys the same scaling, ie., $\mu \to \lambda \mu$. In the scaling region the knowledge of a single point in the MSSM parameter space where the cancellation in the EDMs occur allows one to generate a trajectory in the $m_0-m_{{1/2}}$ plane where the cancellation mechanism holds and the EDMs are small. We illustrate these results for MSSM with radiative electro-weak symmetry breaking constraints. We also discuss a class of D brane models based on Type IIB superstring compactifications which have non-universal phases in the gaugino mass sector and allow large CP violating phases consistent with the EDM constraints through the cancellation mechanism. The scaling in these D brane models and in a heterotic string model is also discussed.