Dark matter is what our universe expands into. The dark matter forces the universe matter through a smaller space which speeds up our expansion and produces dark energy from the friction of dark matter on the universes matter.
As reference, the paper where is described a solution of the rotational velocities observed in spiral galaxies, without using dark matter, is the following (from 2020): article.sapub.org/10.5923.j.astronomy.20200902.01.html
