Is it possible that black holes are responsible for the creation of universes (ie. big bangs)?
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Assumption 1:
As mass collapses in a black hole it will approach a singularity.

Assumption 2:
At some point in time mass reaches the size of planck length (10^-33)

Based on these assumptions, what happens post planck-length sized mass?
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String theory postulates that everything is made up of vibrating strings that are the size of the planck length. According to string theory, an inverse collapse (expansion) will occur to mass after it has reached planck length.

String theory also indicates that gravity passes between dimensions and would be passed from one universe to another. The gravity of the collapsing mass of a black hole would fuel the big bang of a new universe.

Could it be that our universe is a result of a black hole in another universe? Are there multiple universes all interwined in such a fashion? Are black holes the keys to universe creation and destruction?

*Disclaimer: I know relatively little about physics so pardon if this is jibberish or well traversed.

This is quite a common theory, I believe (certainly one I've heard before) but I hadn't heard the string theory bit before. Anyway, as you'll certainly know, there aren't any black holes close enough to Earth to study in an empirical fashion (thankfully), but even this would likely not give an answer to the question.

What would need to be studied is how the star collapses - at what rate does the core collapse between neutron star and black hole changes. If the star collapsed linearly, or exponentially etc., then eventually, the singularity would reach 1 planck length in diameter. However, if it collapsed asymptotically, then it is possible that although the diameter of the black hole would approach the planck length, it would never reach it in a finite amount of time. I don't know nearly enough physics to answer this, but it would depend on how hard it is to get neutrons to share the same space compred to the force of gravity.

Back to the Universe from black holes theory - if this was true, then any universe resulting from a black hole would have only a fraction of the energy/matter of its parent. This would continue down the 'generations' of universes, until you got a Universe with so little matter that forming black holes was impossible.

Also, if you consider that most stars collapsing to form black holes have diameters of at least a million kilometres, then if they were collapsing in a non-asymptotic way, then it is very likely that some black holes from our Universe would have formed child Universes. Anyway what happens to these black holes? If they hang around, then what happens when matter is drawn into the singularity? You should see an increase in energy over time in the child Universe, unless of course, the new Universe's time was not congruent to our own.

Anyway, just some thoughts on the question in hand