Supersymmetric see-saw slow roll inflection point inflation occurs along a MSSM 𝐷-flat direction associated with gauge invariant combination of Higgs, slepton and right-handed sneutrino at a scale set by the right-handed neutrino mass 𝑀_𝜈c ∼ 10⁶−10¹³ GeV. The tensor to scalar perturbation ratio 𝑟 ∼ 10⁻³ can be achieved in this scenario. However, this scenario faced difficulty in being embedded in the realistic new minimal supersymmetric SO(10) grand unified theory (NMSO(10)GUT). The recent discovery of B-mode polarization by BICEP2, changes the prospects of NMSO(10)GUT inflation. Inflection point models become strongly disfavoured, as the trilinear coupling of SUSY see-saw inflation potential gets suppressed relative to the mass parameter favoured by BICEP2. Large values of 𝑟 ≈ 0.2 can be achieved with super-Planck scale inflaton values and mass scales of inflaton ≥10¹³ GeV. In NMSO(10)GUT, this can be made possible with an admixture of heavy Higgs doublet fields, i.e., other than MSSM Higgs field, which are present and have masses of order GUT scale.

We show that a renormalizable theory based on gauge group $SO(10)$ and Higgs system $10\oplus210\oplus126\oplus\bar{126}$ with no scale supergravity can lead to a Starobinsky kind of potential for inflation. Successful inflation is possible in cases where the potential during inflation corresponds to $SU(3)_\rm{C}×SU(2)_\rm{L}×SU(2)_\rm{R}×U(1)_\rm{B−L}, SU(5)×U(1)$ and flipped $SU(5) × U(1)$ symmetries with suitable choice of superpotential parameters. The reheating in such a scenario can occur via non-perturbative decay of inflaton, i.e. through ‘preheating’. After the end of reheating, when Universe cools down, the finite-temperature potential can have a minimum which corresponds to MSSM.