[Qbert]

I can think of two shapes that would account for cosmic acceleration: The torus and the surface of a sphere. I think there are more. My point is this: Does "dark energy" necessarily have to be the culprit for the observed acceleration of the universe's expansion? If we were expanding into a torus or on the surface of a sphere, gravity alone could account for the obseved acceleration. Thus, satisfying occam's razor.

[Guille]

I believe dark energy isn't neccesary at all to explain the xpansion of the universe. Dark energy has been invented to cover a part of physics that phyisicists still can't explain, but I believe generalised it's this: space is made of particles and when certain type of interactions between different matter particles or matter aprticles with force particles, the spacetime aprticles are created. This is why the universe has always grown, grows, and will always grow.