Power law Starobinsky model of inflation from no-scale SUGRA

Understand

We consider a power law $\frac{1}{M^2}R^{\beta}$ correction to Einstein gravity as a model of inflation.

• The interesting feature of this form of generalization is that small deviations from the Starobinsky limit $\beta=2$ can change the value of tensor to scalar ratio from $r \sim \mathcal{O}(10^{-3})$ to $r\sim \mathcal{O}(0.1)$.
• We find that in order to get large tensor perturbation $r\approx 0.1$ as indicated by BKP measurements, we require the value of $\beta \approx 1.83$ thereby breaking global Weyl symmetry.
• We show that the general $R^\beta$ model can be obtained from a SUGRA construction by adding a power law $(\Phi +\bar \Phi)^n$ term to the minimal no-scale SUGRA K\"ahler potential.