A simple nonlocal de Sitter gravity model ($\sqrt{dS}$) is defined by the action $$ S= \frac 1{16\pi G} \int \Big(R-2\Lambda + \sqrt{R-2\Lambda} \mathcal{F}(\Box)\sqrt{R-2\Lambbda\Big)\sqrt{-g}\; \mathrm d^4x. $$ and it shows good properties on cosmological and galactic scales. In this talk we will show that each cosmolgical solution can be described locally by a scalar field. The rotation curves of spiral galaxies (Milky Way and M33) are also well described by the $\sqrt{dS}$ model.
This talk is based on joint work Branko Dragovich, Zoran Rakic and Jelena Stankovic.