Imagine that the universe of space-time is a bubble within an ocean of what we might call dark energy, existing beyond the light (since light exists within space-time). The bubble is made of converted sea water (dark energy). Say that a "shell" of dark energy, (for simplicity of argument) as thick as 10% of the bubble's total diameter, gets converted each instant into expanded universe. This would mean that the total diameter would grow at an accelerating rate that leveled then jumped then leveled, with the length and size of the leaps in acceleration increasing over time. The bigger the universe gets, the faster it expands. Until the remaining amount of dark energy is less than a full "shell" and expansion abruptly ends, if the amount of dark energy is finite. Then the universe might collapse, reverting into dark matter until compressed into the singularity and it all starts again.
Regarding quantum theory, I was thinking about the idea that each particle/field has a large number of probable positions and such, choices if you like, and that the one we vew as real might be only one possibility of the full range that are realized, each possibly in its own universe. It seems to me that if alone in the universe, this might be true, a particle/field -- entity -- could realize all it possibilities at once. However it is not alone. Other entities exist, also with a range of possibilities trying to be realized. Many will overlap with its neighbors strengthening their probability, while others conflict, rule out or cancel one another. And each entity has lots of neighbors. The range of each might be whittled down to just the strongest or most probable, which may have only one realized or may get together in compatible alternate universes. It would take many getting together productively to create a universe.
I lack the complex math skills to test this or know if any of this is even in left field. I would be interested to know.
Regardless it could work for my novels. Alternate realities and metaphysics play large roles.