Palatini NMDC gravity: cosmological scalar field phase portraits in exponential potential

TL;DR

This paper analyzes the cosmological behavior of scalar fields with exponential potentials in Palatini NMDC gravity, comparing it to GR and metric NMDC cases, revealing how Palatini NMDC influences phase space and expansion rates.

Contribution

It introduces a detailed phase space analysis of scalar fields in Palatini NMDC gravity, highlighting differences from GR and metric NMDC models.

Findings

Palatini NMDC restricts acceleration phase in phase space.

Palatini NMDC suppresses the expansion rate compared to GR.

Metric NMDC enhances the expansion rate of GR.

Abstract

We consider cosmological scalar field evolving under exponential potential of the Non-minimal Derivative Coupling (NMDC) gravity model in Palatini formalism. Slow-roll regime is assumed. GR and metric formalism NMDC cases are compared in this study. Phase portraits show that Palatini NMDC effect restricts acceleration phase into smaller region in the phase space. NMDC effect of the Palatini case suppresses expansion rate than that of the GR while the metric NMDC enhances rate of expansion of the GR case.