Can nonlocal gravity really explain dark energy?

TL;DR

This paper explores whether nonlocal modifications to General Relativity can naturally explain the Universe's accelerated expansion without a cosmological constant, by analyzing an Infinite Derivative Gravity model at infrared scales.

Contribution

It demonstrates that nonlocal gravity effects can produce late-time acceleration and offers a new technique to handle complex nonlocal cosmological equations.

Findings

Nonlocal gravity effects can account for accelerated expansion.

Predicted decrease in effective gravitational constant.

Connection established with Starobinsky gravity.

Abstract

In view to scrutinize the idea that nonlocal modifications of General Relativity could dynamically address the dark energy problem, we investigate the evolution of the Universe at infrared scales as an Infinite Derivative Gravity model of the Ricci scalar, without introducing the cosmological constant $\Lambda$ or any scalar field. The accelerated expansion of the late Universe is shown to be compatible with the emergence of nonlocal gravitational effects at sufficiently low energies. A technique for circumventing the mathematical complexity of the nonlocal cosmological equations is developed and, after drawing a connection with the Starobinsky gravity, verifiable predictions are considered, like a possible decreasing in the strength of the effective gravitational constant. In conclusion, the emergence of nonlocal gravity corrections at given scales could be an efficient mechanism to address the dark energy problem.