Revisiting slow-roll inflation in nonminimal derivative coupling with potentials

TL;DR

This paper explores slow-roll inflation within a nonminimal derivative coupling model using various potentials, demonstrating that inflation is more easily achieved than in canonical models due to gravitationally enhanced friction effects.

Contribution

It provides a detailed analysis of slow-roll inflation in NDC models with different potentials, highlighting the ease of inflation implementation compared to canonical coupling.

Findings

NDC model enhances slow-roll inflation even with steep potentials

Inflationary attractors follow the slow-roll equation in phase space

Inflation emerges from saddle points in the autonomous system

Abstract

We investigate the slow-roll inflation in the nonminimal derivative coupling (NDC) model with exponential, quadric, and quartic potentials. It was known that this model provides an enhanced slow-roll inflation induced by gravitationally enhanced friction even for a steep exponential potential. In the phase portrait, the inflationary attractor is described by the slow-roll equation. Introducing the autonomous form, the inflation is regarded as an emergence from the saddle point and it leaves this fixed point along the slow-roll equation. We show explicitly that if one uses the NDC with potentials, the slow-roll inflation is easier to be implemented than the canonical coupling with the same potentials.