Global Supersymmetry on Curved Spaces in Various Dimensions
  We propose methods towards a systematic determination of d dimensional curved spaces where Euclidean field theories with rigid supersymmetry can be defined. The analysis is carried out from a group theory as well as from a supergravity point of view. In particular, by using appropriate gauged supergravities in various dimensions we show that supersymmetry can be defined in conformally flat spaces, such as non-compact hyperboloids $H^{n+1}$ and compact spheres $S^n$ or --by turning on appropriate Wilson lines corresponding to R-symmetry vector fields-- on $S^1 x S^n$, with n<6. By group theory arguments we show that Euclidean field theories with rigid supersymmetry cannot be consistently defined on round spheres $S^d$ if d>5 (despite the existence of Killing spinors). We also show that distorted spheres and certain orbifolds are also allowed by the group theory classification. 
A. Kehagias and J.G. Russo
hep-th