Think about how the universe is expanding, right? The raising bread analogy. The theory states that the further away things are, the faster they are accelerating away from you.
That means at a certain point, space will be expanding relative to your position so fast that light will never be able to break though the barrier than is created, essentially organizing the universe into fractal universes which is what they mean when they talk about multiple "dimensions".
They are just talking about event horizon dimensions that you will never be able to see hear or communicate with while traveling in regular space-time.
idnt that neat?