All of the physicists I named, except Hartle, have raised concerns about the Boltzmann brain problem threatening observational cosmology. Hartle has argued against the SSA, so he thinks Boltzmann brains aren’t problematic. I probably shouldn’t have included his name in the list. Still, the fact that he has published on the issue suggests that he regards it as more than just nonsense.
All of the physicists I named, except Hartle, have raised concerns about the Boltzmann brain problem threatening observational cosmology. Hartle has argued against the SSA, so he thinks Boltzmann brains aren’t problematic. I probably shouldn’t have included his name in the list. Still, the fact that he has published on the issue suggests that he regards it as more than just nonsense.