CP from strings: ideas and problems
  CP has a natural embedding in superstring models as a gauge symmetry involving inversion of the compactified space. Hence the source of CP violation could be geometrical. Such models face the problem of how to suppress contributions to fermion electric dipole moments from softly-broken supersymmetry, as well as other problems of string phenomenology. Stringy symmetries are useful in evaluating models, and rule out some scenarios. 
Thomas Dent (MCTP, University of Michigan)