I'm working on a science fiction novel, a sequel to the best-selling Dark Space series, and I would like to include some reasonable (but fictional) possibilities for how the universe might cycle from expansion to contraction, resulting in a theoretically endless cycle of singularities/big bangs.
This is an age-old question, and far from solved in science, but ideally I would like to inject a fictional force/scenario that could cause the transition from expansion to contraction, and one which does not contradict any currently well-established science.
One hypothetical scenario that I found interesting, is to propose that our universe exists in a configuration of universes that take turns expanding and contracting. When one expanding universe reaches the bounds of another expanding universe, the one with the greatest force of expansion will push back against the space-time barrier of the other one, resulting in its contraction. Once a universe can be forced into contraction, however slowly, gravity does the rest, bringing it back to a singularity.
This seems a logical possibility to my untrained mind, but I wonder if such a configuration could be reasonably expected to go on forever, and whether or not such a system of universes would even work in practice to create the necessary transitions from expansion to contraction.
I'm looking for feedback for my fictional model, and any other theoretical models for how expansion could turn to contraction. By all means refer me to actual research on the subject.