What mechanism is proposed in the Oscillating or Cyclic Universe theory?

Answer

The expansion reverses into a Big Crunch, triggering a subsequent Big Bang.

The Oscillating or Cyclic Universe theory suggests an infinite cycle where expansion is followed by contraction (Big Crunch), which then leads to another Big Bang event.

What mechanism is proposed in the Oscillating or Cyclic Universe theory?
Originsciencetheoryuniversecosmology