We reconsider a class of well motivated supersymmetric models in which inflation is associated with the breaking of a gauge symmetry G to H , with the symmetry breaking scale M \sim 10 ^ { 16 } GeV .
Starting with a renormalizable superpotential , we include both radiative and supergravity corrections to derive the inflationary potential .
The scalar spectral index n _ { s } can exceed unity in some cases , and it can not be smaller than 0.98 if the number of e-foldings corresponding to the present horizon scale is around 60 .
Two distinct variations of this scenario are discussed in which non-renormalizable terms allowed by the symmetries are included in the superpotential , and one finds n _ { s } \geqslant 0.97 .
The models discussed feature a tensor to scalar ratio r \lesssim 10 ^ { -4 } , while \textrm { d } n _ { s } / \textrm { d } \ln k \lesssim 10 ^ { -3 } .
If G 
corresponds to SO ( 10 ) or one of its rank five subgroups , the observed baryon asymmetry is naturally explained via leptogenesis .