One loop effective potential in heterotic M-theory
  We have calculated the one loop effective potential of the vector multiplets arising from the compactification to five dimensions of heterotic M-theory on a Calabi-Yau manifold with h^{1,1}>1. We find that extensive cancellations between the fermionic and bosonic sectors of the theory cause the effective potential to vanish, with the exception of a higher order curvature term of the type which might arise from string corrections. 
Ian G. Moss, James P. Norman