Power law Starobinsky model of inflation from no-scale SUGRA
  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. We further show that this two parameter
power law generalization of the Starobinsky model is equivalent to generalized
non-minimal curvature coupled models with quantum corrected $\Phi^{4}$-
potentials i.e. models of the form $\xi \Phi^{a} R^{b} + \lambda
\Phi^{4(1+\gamma)}$ and thus the power law Starobinsky model is the most
economical parametrization of such models.
