In order to explain the late-time cosmological acceleration, we propose a new pure geometric gravity based on Deser-Woodard theory [Phys. Rev. Lett. 99, 111301 (2007)], in which the expansion of a matter-dominated universe can be accelerating. This new theory behaves as well as general relativity in solar system and gravitational waves, which is an important improvement over Deser-Woodard nonlocal gravity. Especially, for the simplest case, theoretical considerations determine all the parameters that appear in the Lagrangian.

• Received 30 August 2018

DOI:https://doi.org/10.1103/PhysRevD.98.084040