The Starobinsky Model from Superconformal D-Term Inflation

TL;DR

This paper shows that the superconformal D-term inflation model aligns with the Starobinsky model in the large field regime, providing a unified description of inflation related to grand unification scale physics.

Contribution

It demonstrates the equivalence of superconformal D-term inflation and the Starobinsky model in the large field limit, linking inflationary dynamics to grand unification scale parameters.

Findings

In the large field regime, the models coincide.

Inflation is realized with large gauge couplings.

The effective coupling relates to the GUT scale.

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 {\lambda} 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 {\lambda} ~ (\Lambda_{GUT}/M_P)^4.