The black hole information paradox

Assembled from 28 blocks · 2 evidence · 18 related

1. Story
2. The unresolved conflict between two principles that are each extremely well supported. Quantum mechanics is unitary: the state of a closed system evolves reversibly, so in principle the past is always recoverable from the present. Hawking argued in 1976 that a black hole violates this, because the radiation it emits is thermal - determined by mass, spin and charge alone - so when the hole finishes evaporating, everything that distinguished what fell in is gone. Don Page sharpened the problem in 1993 by pointing out what unitarity requires of the entanglement entropy of the radiation: it must rise, turn over at roughly the halfway point of evaporation, and fall back to zero. Hawking's calculation gives a curve that only rises. Since 2019, calculations using replica wormholes and the so-called island formula have reproduced the Page curve from within semiclassical gravity, which most workers regard as major progress. It is not a solution: the computation says the entropy behaves as unitarity demands without saying by what mechanism information escapes. Not a place on Earth.
3. Knowledge
4. The no-hair result
5. Hawking radiation
6. The black hole information paradox
7. Connections
8. Hawking radiation
9. The no-hair result
10. Hawking argues that information is destroyed
11. Page states what unitarity requires of the radiation
12. Hawking concedes the information bet
13. The Page curve is reproduced from within semiclassical gravity
14. Stephen Hawking
15. Black hole entropy
16. The black hole information paradox
17. Hawking shows that black holes radiate
18. Hawking argues that information is destroyed
19. The Page curve is reproduced from within semiclassical gravity
20. The Kerr solution and black hole spin
21. The black hole information paradox
22. Kerr finds the rotating solution
23. The term "black hole" enters use
24. Hawking argues that information is destroyed
25. GW150914 - two black holes merge and the signal reaches Earth
26. Evidence
27. Argues that black hole evaporation destroys information and therefore conflicts with the unitarity of quantum mechanics. V55 VERIFICATION BASIS: not consulted in session; no research tool was available. Volume and page are from recall and must be checked.
28. States the entanglement-entropy behaviour that unitary evaporation requires, now known as the Page curve. V55 VERIFICATION BASIS: not consulted in session; no research tool was available. Volume and page are from recall and must be checked. The 2019-2020 island and replica-wormhole papers that reproduce this curve are deliberately NOT cited anywhere in this pack, because their authors and venues could not be confirmed.