Higher derivative operators from Scherk-Schwarz supersymmetry breaking on Script T2/Z2.

In orbifold compactifications on T^2/Z_2 with Scherk-Schwarz supersymmetrybreaking, it is shown that (brane-localised) superpotential interactions and(bulk) gauge interactions generate at one-loop higher derivative countertermsto the mass of the brane (or zero-mode of the bulk) scalar field. Thesebrane-localised operators are generated by integrating out the bulk modes ofthe initial theory which, although supersymmetric, is neverthelessnon-renormalisable. It is argued that such operators, of non-perturbativeorigin and not protected by non-renormalisation theorems, are generic inorbifold compactifications and play a crucial role in the UV behaviour of thetwo-point Green function of the scalar field self-energy. Their presence in theaction with unknown coefficients prevents one from making predictions aboutphysics at (momentum) scales close to/above the compactification scale(s). Ourresults extend to the case of two dimensional orbifolds, previous findings forS^1/Z_2 and S^1/(Z_2 x Z_2') compactifications where brane-localised higherderivative operators are also dynamically generated at loop level, regardlessof the details of the supersymmetry breaking mechanism. We stress theimportance of these operators for the hierarchy and the cosmological constantproblems in compactified theories.Comment: 23 pages, LaTeX, one figure, published version in JHE