Modified gravity: walk through accelerating cosmology

TL;DR

This paper reviews various modified gravity theories explaining cosmic acceleration, focusing on singularities, their removal, unification of inflation and dark energy, and explores solutions like domain walls and higher derivative gravity.

Contribution

It provides a comprehensive overview of accelerating cosmologies in modified gravity, including singularity removal techniques and unification scenarios, with new insights into domain wall solutions and higher derivative models.

Findings

Finite-time future singularities can be removed with R^2 terms.

Unification of inflation and late-time acceleration is achievable in F(R) gravity with Lagrange multipliers.

Domain wall solutions and covariant higher derivative gravity models are explored.

Abstract

We review the accelerating (mainly, dark energy) cosmologies in modified gravity. Special attention is paid to cosmologies leading to finite-time future singularities in $F(R)$, $F(G)$ and $\mathcal{F}(R,G)$ modified gravities. The removal of the finite-time future singularities via addition of $R^2$-term which simultaneously unifies the early-time inflation with late-time acceleration is also briefly mentioned. Accelerating cosmology including the scenario unifying inflation with dark energy is considered in $F(R)$ gravity with Lagrange multipliers. In addition, we examine domain wall solutions in $F(R)$ gravity. Furthermore, covariant higher derivative gravity with scalar projectors is explored.