One grad student would probably not be sufficient to sus out the truth of my pet theory hypothesis (please). My hypothesis is that dark matter and dark energy are the felt effects of virtual particles (dark mass) poofing into existence constantly via quantum fluctuations in the vacuum between dispersed atoms in space, and the energy released when the particle/anti-particle pair reunite and self annihilate (dark energy). Since E = MC^2, dark energy would be greater than dark matter by a large amount, as it is. That ratio would be controlled by how many virtual particles self annihilate versus how many persist (the current unknown), forming non-virtual elementary particles that add to the total non-virtual mass of the Universe.
If this is the case, then the Universe would be expanding, and it is. The rate of expansion would keep accelerating, and it is. And it’s quite possible that some critical amount of expansion might create an excess of energy and mass that would trigger a new Big Bang; so the big rip is the trigger, not a once posited big crunch.