Abstracts

Branko Dragovich

The dark side of the universe in a nonlocal de Sitter gravity

I will present several exact vacuum cosmological solutions of a simple nonlocal de Sitter gravity model. One of these solutions mimics effects that are usually assigned to dark matter and dark energy and is in a very good agreement with the standard model of cosmology, i.e. we obtained: 68.5% of dark energy, 26.6% dark matter and 4.9% visible matter [1.2]. In this model the Hubble parameter depends on cosmic time and currently is H= 67.40 km/s/Mpc. I plan mainly discuss dark energy and dark matter aspects of this nonlocal de Sitter model. Some other solutions are examples of the nonsingular bounce ones in flat, closed and open universe. There are also singular and cyclic solutions. Recently, we considered the rotation curves for the Milky Way and the spiral galaxy M33 and have obtained very good agreement with experimental data, see [3]. All these cosmological and galaxy solutions are a result of nonlocality in the cosmological constant background and do not exist in the local de Sitter case.

This talk is mainly based on our papers: 1) PLB 797 (2019) 134848, 2) JHEP 12 (2022) 054 and 3) Symmetry 2024, 16, 544.