[mpc755]

There's no need for negative mass.

Some of the matter falling towards a supermassive black hole is converted into energy. This energy is delivered to the surrounding gas, and leads to large outflows of matter, which stretch for hundreds of thousands of light years from the black holes, reaching far beyond the extent of their host galaxies.

Our visible universe is in the outflow of a universal black hole. As ordinary matter falls toward the universal black hole it evaporates into dark matter. It is the dark matter outflow which pushes the galaxy clusters, causing them to move outward and away from us. The dark matter outflow is dark energy.

The galaxy clusters which have been pushed for longer than we have are accelerating outward and away from us. We are accelerating outward and away from the galaxy clusters which have been pushed for less time than we have. From our perspective most of the galaxy clusters are accelerating away from us.

Dark energy is the dark matter outflow associated with our universal black hole.

You toss a bunch of ping pong balls into a fast flowing stream. As long as the stream is flowing faster than the ping pong balls the ping pong balls are going to accelerate. As the ping pong balls empty into a lake, again, as long as the stream is flowing faster than the ping pong balls, the ping pong balls are going to continue to accelerate as they move outward and away from one another.

In the analogy, the fast flowing stream emptying into the lake is dark energy, the water is dark matter and the ping pong balls are the galaxy clusters. The ping pong balls displace the water. The water pushing back and exerting pressure toward the ping pong balls is gravity.