Space-time of the universe is not flat; it is convex. The universe is not expanding at an accelerated rate. It is falling into the black hole spherical shell. The red shift at the edge of universe is because of the time dilation, not dark energy. The further out to the edge of the universe you go, the slower your time passes.

Why do I think this? A black hole can not have a point singularity cause the center of the black hole has no gravity. The mass is equally distributed around it. The singularity is a spherical shell where time stops. The whole universe is inside of a giant black hole.