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Black Holes

Black Holes. Eternal? Or just long lived?. by Patrick Murphy. A Brief History Of Black Holes. First proposed in thought experiment by John Mitchell in 1783 1916: Karl Schwarzschild solves Einstein’s field equation for spacetime around a spherical body. A little more on Einstein….

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Black Holes

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  1. Black Holes Eternal? Or just longlived? by Patrick Murphy

  2. A Brief History Of Black Holes. • First proposed in thought experiment by John Mitchell in 1783 • 1916: Karl Schwarzschild solves Einstein’s field equation for spacetime around a spherical body. • A little more on Einstein….

  3. General Relativity • Published in 1915 • Describes the relationship between mass and spacetime. • Spacetime tells mass how to move and mass tells spacetime how to curve. • Confirmed in 1919 by Arthur Eddington

  4. Spacetime: • Apparent vs. real trajectory of a light beam

  5. Solved metric for spacetime surrounding a spherical mass. Schwarzschild metric: Schwarzschild radius : Karl Schwarzschild

  6. Classic Black Holes • 1939 : Oppenheimer shows massive stars collapse to a singular point. • Multiple solutions involving small perturbations confirm results. • Singularity surrounded by event horizon, point of no return. • Three parameters : Mass, Charge and Spin

  7. Classic Black Holes Roger Penrose • 1969: Proved all full gravitational collapses result in a singularity • Postulated Cosmic Censorship Law

  8. Schwarzschild Static, no rotation Point-like singularity Event Horizon Kerr Rotates Ring shaped singularity Inner Horizon Outer Horizon Ergosphere 2 main types

  9. Schwarzschild Kerr 2 main types

  10. So nothing can escape the gravitational attraction of the black hole once past the event horizon? Classically, yes

  11. Problems with classical theory • Assumed TBH = 0 K, despite mathematical evidence to the contrary . • No thermal spectrum • Singularity too small for Relativity

  12. Can Black Holes Radiate? Maybe so… • 1970 : Jacob Berkenstein suggests area of event horizon is a measurement of black holes entropy. • 1970 : Stephen Hawking shows that area of event horizon always increases. • 1971 : Borisovitch Zel’dovitch claims rotating black holes radiate until they stop spinning .

  13. 1974: Hawking Radiation • Hawking repeats Zel’dovitch’s calculatons. • Agrees except…. • Finds they continue to radiate! • There’s more… • His solution predicted the emission spectrum to be exactly that of a hot body. • That means temperature and entropy

  14. How can it radiate? • Various mechanisms are possible, depending on your frame of reference. • They all acknowledge quantum vacuum fluctuations as source. • Quantum vacuum fluctuations are unavoidable due to Heisenberg’s Uncertainty Principle

  15. And…? • Say you’re safely at rest, watching vacuum fluctuations. • You see a virtual pair of photons created just outside the event horizon. • Tidal gravity pulls them apart, they become real. • One gets sucked in, the other escapes forever.

  16. So What’s Left? • Resolution of the “Information paradox” • Development of an adequate quantum theory of gravity, Relativity is no longer a valid approximation on scales smaller than the Planck length, lp = (hG/2πc3)1/2 .

  17. Information loss? • In technical jargon, the black hole has performed a non-unitary transformation on the state of the system.  As you may recall, non-unitary evolution is not allowed to occur naturally in a quantum theory because it fails to preserve probability. • Hawking suggests that black hole radiation contains information about what went in, albeit in a mangled form.

  18. Branes? • P brane: length in p dimensions • P = 1 : String • P = 2 : Membrane • Etc… • Information stored

  19. Quantum Gravity? • Singularities are tiny • Quantum foam • No time, how space manifests itself is probabilistic • Many candidates, include : M-theory, Supergravity, AdS/CFT , holography …

  20. So Why study Black holes? • Black holes push the limits of physical theories • Among the most extreme phenomena in the universe • I think they’re cool. • That’s it • Thanks for listening • The End • (applause…. please?)

  21. Kip Thorne, Black Holes And Timewarps (Norton, 1994) Eric Poisson, A Relativist's Toolkit, The mathematics of black hole mechanics (Cambridge University Press, 2004). Alessandro Fabbri and Jos\'{e} Navarro-Salas,Modeling Black Hole Evaporation (Imperial College Press, 2005) John A. Wheeler, E.F. Taylor, Exploring Black Holes, Introduction to General Relativity (Addison Wesley, 2000) Stephen Hawking, The Universe In A Nutshell (Bantam, 2001) Images : http://chandra.harvard.edu/resources http://www.belmontnc.4dw.net/DWFNEU5.gif www.tqnyc.org/NYC040808/ neutron_star.jpg http://en.wikipedia.org www.scienceweek.at References :

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