I think that’s the gist actually. Unitarity does seem to raise problems in the cosmos (information loss) but naively violating it by adding a photon gets you th

I think that’s the gist actually. Unitarity does seem to raise problems in the cosmos (information loss) but naively violating it by adding a photon gets you this ridiculous paradox of black holes turning into photons. So if you’re going to relax the unitarity assumption, you have to do it carefully. I guess this is their program with isometry.