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i understand that the Pauli exclusion principle states that two fermions cannot occupy the same quantum state.

This question is not about a black hole. It is more about the singularity at moment of the big bang, that had every mass in the universe in a single point, that had no spatial extension.

The uncertainty principle states that it gives a fundamental limit to the limit with which certain pairs of properties of particles can be known.

I understand that a singularity has no spatial extension.

Question:

  1. Does a singularity (especially at the moment of big bang) violate the Pauli principle? So the principles were not in force before the Big Bang?
Qmechanic
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Árpád Szendrei
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1 Answers1

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A singularity does not violate the Pauli principle, because the composition of a black hole is fundamentally untestable. If two fermions fall into a black hole, maybe they annihilate, maybe they don't, but in the end you could never observe the inside of the black hole and see that it is made up of separate parts. And as the saying goes: if it's not testable (in principle), it's not physics.

Black holes can have spin, and so it might be possible for the entire black hole to in fact be fermionic, but that's not the same as having multiple constituent parts that are fermionic.

Your question is a great gateway to the discussion of what exactly happens to all the information about these pieces that have fallen into a black hole. See black hole complementarity and the "firewall" to read more about that.

Martin Lichtman
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