Consistent modified gravity: dark energy, acceleration and the absence of cosmic doomsday

TL;DR

This paper explores modified gravity models with curvature-dependent terms that can explain cosmic acceleration and dark energy, potentially avoiding cosmic doomsday scenarios.

Contribution

It demonstrates how including negative and fractional powers of curvature in modified gravity can produce dark energy effects and avoid future cosmic collapse.

Findings

Negative curvature powers can induce cosmic acceleration.

Fractional positive powers lead to effective phantom dark energy.

Adding an R^2 term helps prevent cosmic doomsday.

Abstract

We discuss the modified gravity which includes negative and positive powers of the curvature and which provides the gravitational dark energy. It is shown that in GR plus the term containing negative power of the curvature the cosmic speed-up may be achieved, while the effective phantom phase (with $w$ less than -1) follows when such term contains the fractional positive power of the curvature. The minimal coupling with matter makes the situation more interesting: even 1/R theory coupled with the usual ideal fliud may describe the (effective phantom) dark energy. The account of $R^2$ term (consistent modified gravity) may help to escape of cosmic doomsday.