Generalized modified gravity with the second order acceleration equation

TL;DR

This paper introduces a class of generalized modified gravity theories with second-order acceleration equations, simplifying the analysis of cosmic evolution and addressing key cosmological problems like singularities and acceleration.

Contribution

It proposes a new class of theories with second-order acceleration equations, making cosmic evolution and weak-field analysis more tractable.

Findings

Addresses Big-bang singularity problem

Explains current cosmic acceleration

Simplifies analysis of universe evolution

Abstract

In the theories of generalized modified gravity, the acceleration equation is generally fourth order. So it is hard to analyze the evolution of the Universe. In this paper, we present a class of generalized modified gravity theories which have the acceleration equation of second order derivative. Then both the cosmic evolution and the weak-field limit of the theories are easily investigated. We find that not only the Big-bang singularity problem but also the current cosmic acceleration problem could be easily dealt with.