But until recent improvements in numerical relativity schemes, numerical analysis was unreliable near the singularity for reasons which I discussed in my post on numerical relativity, which is archived on my relativity page. But the latest numerical work and the new nonlinear analysis by Gnedin and Gnedin seems to be converging on a fairly simple and coherent set of predictions.
Time runs vertically and r increases to the right.
For simplicity I'll omit this strip from the discussion. Next, consider a shell which is initially smaller or not initially expanding as rapidly.