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CREA Black Holes

Lecture series CREA, UvA, March 9, 2011

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CREA Black Holes

  1. 1. BLACK HOLE HORIZONS: The Gravity of ParadigmsSebastian de HaroAmsterdam University CollegeCREA, March 9, 2011
  2. 2. EINSTEIN’S HOLY GRAIL• Search for unified theory.• Incorporate relativity.• Reject QM.
  3. 3. PHYSICS’ HOLY GRAIL: UNIFICATION• Relativity and quantum theory.
  4. 4. PHYSICS’ HOLY GRAIL: UNIFICATION• Relativity and quantum theory• Look for clues: black holes.• Both relativity and quantum mechanics play a role.
  5. 5. PLAN• Classical properties of black holes.• Quantum black holes: they are not black. • Information paradox.• Complementarity of observers.• Holographic principle.
  6. 6. WHAT ARE BLACK HOLES?• Pierre-Simon Laplace (1749-1827). • Escape velocity. • Earth: 𝑣 = 11,2 km/s • ‘Black star’: 𝑣 = 299 972 km/s
  7. 7. WHAT ARE BLACK HOLES?• Einstein 1915: mass implies curvature of space-time.• Curvature is perceived as gravitational attraction.
  8. 8. WHAT ARE BLACK HOLES?
  9. 9. OBSERVATIONAL EVIDENCE• Black hole itself cannot be seen.• Indirect evidence: matter swallowed up by supermassive black object.• Predictions: time delay, gravitational lensing.
  10. 10. OBSERVATIONAL EVIDENCE• Black hole itself cannot be seen.• Indirect evidence: matter swallowed up by supermassive black object.• Predictions: time delay, gravitational lensing.
  11. 11. HOW LARGE IS A BLACK HOLE? 2𝐺𝑀 𝑅= 2 𝑐• If as heavy as the sun: one meter.• Supermassive (one million suns): size of the solar system.• Milky Way: Sagittarius A*.
  12. 12. SONIC BLACK HOLES
  13. 13. SONIC BLACK HOLES
  14. 14. THE RELATIVITY OF GRAVITY• Free fall.
  15. 15. SUMMARY – PROPERTIES OF BLACK HOLES• Heaviest objects, not even light can escape.• Fish in the water analogy.• Free fall.
  16. 16. HAWKING: BLACK HOLES AIN’T SO BLACK• 1973 Bekenstein develops black hole thermodynamics. 𝑘𝑐 3 𝐴• 1974 Hawking: black holes emit radiation. 𝑆= 4𝐺ℏ ℏ𝑐 3 𝑇= = 6,2 × 10−8 K 8𝜋𝐺𝑀𝑘• The key: quantum fluctuations of vacuum.
  17. 17. HAWKING RADIATION
  18. 18. • 1973 Bekenstein develops the thermodynamics of black holes 𝑘𝑐 3 𝐴 𝑆=• 1974 Hawking: black holes can emit radiation! 4𝐺ℏ ℏ𝑐 3 𝑀 −8 ʘ K 𝑇= = 6,2 × 10 8𝜋𝐺N 𝑀𝑘 𝑀
  19. 19. HAWKING’S PROVOCATIVE CONCLUSION• If we wait long enough, black hole evaporates.• The radiation does not contain information about what went in.• Information forever lost.• Black holes violate the laws of physics.
  20. 20. INFORMATION LOSS
  21. 21. INFORMATION LOSS
  22. 22. SUMMARY – HAWKING’S ARGUMENT• Black holes emit radiation.• The radiation is thermal, contains no information.• Information is lost.• New level of unpredictability in physics.
  23. 23. INTERMEZZO – AN EXPERIMENT
  24. 24. INTERMEZZO – AN EXPERIMENT
  25. 25. INTERMEZZO – AN EXPERIMENT
  26. 26. INTERMEZZO – AN EXPERIMENT
  27. 27. INTERMEZZO – AN EXPERIMENT
  28. 28. COMPLEMENTARITY
  29. 29. ALICE IN WONDERLAND
  30. 30. ALICE IN WONDERLAND
  31. 31. ALICE IN WONDERLAND
  32. 32. ALICE IN WONDERLAND
  33. 33. SONIC BLACK HOLES
  34. 34. ALICE IN WONDERLAND
  35. 35. ALICE’S VIEW
  36. 36. AN EXPERIMENT
  37. 37. SUMMARY – BLACK HOLE COMPLEMENTARITY• Alice and the cat have different descriptions of reality.• Their points of view are mutually exclusive.• Describe black hole from point of view of an observer.• Led to holographic principle.
  38. 38. HOLOGRAPHY (BBC Horizon, 2011)
  39. 39. 𝑘𝑐 3 𝐴 𝑆= 4𝐺ℏ Gravity in bulk ⇔boundary theory
  40. 40. 2𝐺N 𝑀 𝑅s = 2 ~𝐸 𝑐THE DISCOVERY OF HOLOGRAPHY 𝑘𝑐 3 𝐴 𝑆BH = 4𝐺ℏ• 1993 ’t Hooft• Gedanken experiment: box volume 𝑅 3 ER• Entropy: measure of # of physical states 𝑘𝑐 3 𝐴 S~E # 𝑆< 4𝐺ℏ Gravity in bulk ⇔ boundary theory
  41. 41. HOLOGRAPHY• ’t Hooft 1993 “dimensional reduction” 𝑘𝑐 3 𝐴 𝑆= 4𝐺ℏ• Susskind 1994 “holography”• Maldacena 1997 holography in string theory• 2004 Hawking admits he lost his bet
  42. 42. HAWKING’S 2005 PAPERThere is no baby universe branching off, as I once thought. Theinformation remains firmly in our universe. I’m sorry to disappoint sciencefiction fans, but if information is preserved, there is no possibility of usingblack holes to travel to other universes. If you jump into a black hole, yourenergy will be returned to our universe but in a mangled form whichcontains the information about what you were like but in a state where itcan not be easily recognized. It is like burning an encyclopedia.Information is not lost, if one keeps the smoke and the ashes. But it isdifficult to read. In 1997, Kip Thorne and I, bet John Preskill thatinformation was lost in black holes. The loser(s) of the bet were to providethe winner(s) with an encyclopedia of their own choice, from whichinformation can be recovered with ease. I gave John an encyclopedia ofbaseball, but maybe I should just have given him the ashes.
  43. 43. SUMMARY• Black holes can radiate, which gives rise to information paradox• Paradigm to solve this problem: holography – confirmed by string theory: the world is 3- not 4-dimensional• Gravity is a “fake” force• Implications for reductionism?
  44. 44. SCIENCE & CULTURE BLACK HOLES IN De Gids• Prof. dr. F.H. van Lunteren: • Essays: Gerard ‘t Hooft, Vincent Influence of cultural and Icke, Ed van den Heuvel, Michiel philosophical climate of van der Klis, John Wheeler, quantum mechanics during Jeroen van Dongen, Sebastian de Haro Weimar Republic, March 29.• WWW.HETWERELDBEELD.NL • Poems: Leo Vrooman, Maria Barnas, Rogi Wieg, Mustafa Stitou, Jan Baeke

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