The Starobinsky Model from Superconformal D-Term Inflation

Abstract

We point out that in the large field regime, the recently proposed superconformal D-term inflation model coincides with the Starobinsky model. In this regime, the inflaton field dominates over the Planck mass in the gravitational kinetic term in the Jordan frame. Slow-roll inflation is realized in the large field regime for sufficiently large gauge couplings. The Starobinsky model generally emerges as an effective description of slow-roll inflation if a Jordan frame exists where, for large inflaton field values, the action is scale invariant and the ratio \hat λ of the inflaton self-coupling and the nonminimal coupling to gravity is tiny. The interpretation of this effective coupling is different in different models. In superconformal D-term inflation it is determined by the scale of grand unification, \hat λ ~ (Λ_{GUT}/M_P)^4.

Figures (1)

• Figure 1: Comparison of $R^2$ inflation (dashed line) and superconformal D-term inflation (solid line) for $gq = 4\sqrt2$, $\lambda = 1$, $\chi = -10$ and $N_* = 55$. The slow-roll regimes are $[\phi_{\epsilon}^R,\phi_*^R]$ and $[\phi_\eta,\phi_*]$, respectively.