Phantom crossing in viable $f(R)$ theories

TL;DR

This paper reviews the behavior of dark energy's equation of state in viable $f(R)$ gravity models, highlighting the common phenomenon of crossing the phantom divide in the universe's past and future.

Contribution

It provides a summary of the generic phantom divide crossing feature in viable $f(R)$ gravity models, emphasizing its significance in cosmic evolution.

Findings

Phantom divide crossing occurs in both past and future in $f(R)$ models.

The review highlights the generic nature of this crossing in viable theories.

Implications for dark energy dynamics in modified gravity.

Abstract

We review the equation of state for dark energy in modified gravity theories. In particular, we summarize the generic feature of the phantom divide crossing in the past and future in viable $f(R)$ gravity models.