from that black hole, which is kinda obvious since the black hole no longer exists.
But three points:
1. I think the black hole has to be supermassive for the mechanisms stated in Greene's book to be operative. But no one has specified just how big supermassive is. Therefore the creation mechanism ceases long before the black hole evaporates.
2. In essence black holes do not evaporate. The evaporation rate is so tiny compared to the mass of any supermassive black hole that we can safely say that they just do not evaporate. For example, the absorption of one star in a black hole can offset billions of years of evaporation.
3. I suspect that black holes reach a max mass, but this has never been quantified. It would be worth at least a NATURE article if it were. My opinion comes from the fact that supermassive black holes must convert mass into the unified within its singularity. Since the unified field is massless, purely bosonic, then the black hole is effectively destroying mass. The destroyed mass then goes into making new universes. However, the effect on the mother universe is to limit the amount of mass a black hole could contain. Once the mass is sufficient for the planck scale energy to be exceeded, a portion of the mass goes through a phase transformation that converts it into the massless unified field.
A question in my mind then is:
Does the black hole have to absorb new mass every time it creates a new universe? If so then rather few new universes are being created at any one time as most black holes, like the one in the Milky Way, are not actively absorbing mass.
Then there is the question of how just a bit of absorbed mass, like one star, could generate a whole new universe. The answer may be that the balance of energy in a universe is actually zero. The expansion of the universe provides the energy for its creation. That does not sound right, but math says that our univere could have come from a quantum fluctuation, which essentially has no energy in it. It just creates a false vacuum which stroes upa tremendous amount of energy from expansion or rather inflation, which then becomes the big bang. So no energy is needed to create universes, just a triggering mechanism.
So then when a black hole becomes big enough to exceed the threshold for universe creation, it will presumably create one. Does the black hole then drop below the threshold? If so, then that puts a max size on black holes do to universe creation. If not then there is no loss to the black hole when it creates a universe and supermassive black holes can increase to any size.
By the way, a poem of the Hottentot people of Africa that I posted on this forum log ago, essentially predicts the creation of universes once the black hole has absorbed enough mass. So some being (perhaps god)or beings out there know more about this than humans do. We see similar hints in other scripture. Superstring compactification of dimensions is discussed in the jewish book of creation, supposedly written by abraham. The sri bagavatam and other hindu scriptures discuss quarks. And the Koran discusses universe expansion and black holes. I take this to be an argument against fundamentalism and its condemnation of science. Since the science is already hinted at in scripture of many faiths, the only conclusion is that science is a good, or maybe even a god thing.