We consider a simplified version of supersymmetric smooth hybrid inflation which contains a single ultraviolet cutoff m _ { P } = 2.4 \times 10 ^ { 18 } GeV , instead of the two cutoffs m _ { P } and M _ { * } \sim few \times 10 ^ { 17 } GeV that are normally employed .
With global supersymmetry the scalar spectral index n _ { s } \simeq 0.97 , which is in very good agreement with the WMAP observations .
With a non-minimal Kähler potential , the supergravity version of the model is compatible with the current central values of n _ { s } and also yields potentially observable gravity waves ( tensor to scalar ratio r \lesssim 0.02 ) .