Assuming the big rip scenario is possible, what happens exactly at $t=t_{rip}$? Is spacetime really ripped?

Question

I want to start by prefacing a scenario. Say equation of state is $w<-1$ and we live in a phantom dark energy dominated universe. This means in a finite time the cosmological scale factor reaches infinity and the cosmic event horizon reaches 0 in a finite time (i.e. as $t \to t_{rip}$). The expansion then starts first disassociating structures that are gravitationally bound (galaxies, planets, etc), then structures that are electromagnetically bound such as atoms and then their nuclei and finally nucleons into their fundamental constituent. I am assuming that the expansion also overpowers any quantum gravitational effects and even color confinement. Does anything exist at this point? Can a quantum field exist if the cosmological event horizon is $0$?

I only ask this question because many mainstream science articles and even academic journals all talk about how even spacetime is ripped? What does that actually entail?

Answer 1

We really don't know the answer, since it would require a theory of quantum gravity.

The paper which suggests the Big Rip scenario is only 4 pages, and can be read in arXiv. In the end, the authors declare

In all likelihood, some new physics (e.g., spontaneous particle production or extra-dimensional, string, and/or quantum-gravity effects) may kick in before the ultimate singularity, but probably after the sequence of events outlined above.