How successful can the scalar-tensor theory be in understanding the accelerating universe?

TL;DR

This paper explores how scalar-tensor theories can naturally explain the small observed cosmological constant without fine-tuning, addressing key issues in understanding the universe's acceleration.

Contribution

It demonstrates that scalar-tensor theories offer a simple, natural explanation for the smallness of the cosmological constant in the context of the universe's age.

Findings

Scalar-tensor theories can account for the universe's acceleration without fine-tuning.

The small cosmological constant is linked to the universe's age in this framework.

The approach provides a natural solution to the cosmological constant problem.

Abstract

The accelerating universe is closely related to today's version of the cosmological constant problem; fine-tuning and coincidence problems. We show how successfully the scalar-tensor theory, a rather rigid theoretical idea, provides us with a simple and natural way to understand why today's observed cosmological constant is small only because we are old cosmologically, without fine-tuning theoretical parameters extremely.