Cosmological constant in F(R) supergravity

TL;DR

This paper calculates a positive cosmological constant within a specific F(R) supergravity model, extending its application from high to low curvature regimes, and shows it can violate the Strong Energy Condition.

Contribution

It demonstrates that a simple extension of cubic F(R) supergravity allows for a positive cosmological constant at low curvature, broadening the model's cosmological implications.

Findings

Positive cosmological constant achieved in low curvature regime

Extension of F(R) supergravity model from high to low curvature

Violates the Strong Energy Condition, enabling positive cosmological constant

Abstract

A cosmological constant in the regime of low space-time curvature is calculated in the recently proposed version of F(R) supergravity with a generic cubic function F. The F(R) supergravity is the N=1 supersymmetric extension of f(R) gravity. The cubic model is known to successfully describe a chaotic (slow-roll) inflation in the regime of high space-time curvature. We find that a simple extension of the same model allows a positive cosmological constant in the regime of low space-time curvature. The inflaton superfield in F(R) supergravity (like inflaton in f(R) gravity) violates the Strong Energy Condition and thus breaks the restriction of the standard supergravity (with usual matter) that can only have either a negative or vanishing cosmological constant.