Does dark matter slow down growth of the universe?
Dark matter does slow down the growth of it – via gravity, BUT importantly, there are alot of other (heavier) factors that speed it up. Einstein theorized a “static” universe, but realized a problem that when he put all the mass together, we should at best be speeding towards each other, at worst slowing down the rate at which we are expanding from the explosion, so he included the idea of the cosmological constant as a repulsive force to balance the universe and make it static. As it so happens, he ended up regretting it, but didn’t live to see the day where he was vindicated, in 1998 when people noticed the acceleration of the universe is progressively increasing, due to the dark ENERGY contribution. The dark matter, however, does slow down the rate of growth, as I said, via gravity (the only method that dark matter interacts with the surrounding world).
