A realistic tribrid model of sneutrino inflation is constructed in an R -symmetric SU ( 5 ) grand unified theory ( GUT ) .
To avoid the monopole problem , a pseudosmooth inflationary trajectory is generated with the help of an additional Z _ { 5 } symmetry which is broken during and after inflation .
The predictions of inflationary parameters are made at the central value of the scalar spectral index , n _ { s } = 0.968 .
The largest possible value of the tensor to scalar ratio , r \lesssim 0.0027 , is obtained with sub-Planckian field values ( \lesssim m _ { P } ) .
A successful realization of reheating and leptogenesis is achieved by avoiding the gravitino problem with a reheat temperature as low as 10 ^ { 6 } GeV .
The predicted range of the gauge symmetry breaking scale , 5 \times 10 ^ { 16 } \lesssim M / \text { GeV } \lesssim 5 \times 10 ^ { 17 } , turns out to be somewhat larger than the typical GUT scale .
With additional vector-like families , a successful gauge coupling unification is achieved by avoiding the no-go theorem related to R -symmetric SU ( 5 ) GUT .