Bob Nichol - Nobel Prize Public Talk

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Bob Nichol - Nobel Prize Public Talk

  1. 1. The Nobel Prize in Physics 2011 Bob Nichol (ICG Portsmouth) “majority of its surface area is only about 10 feet above sea level”
  2. 2. General Relativity Primer
  3. 3. Cosmology Primer I   Assumptions   Cosmological Principle; not special place, time or physics   Homogeneous and isotropic; defines “simple” FRW metric   Assume GR and FRW metric; solve to get Friedmann’s equations (including Einstein’s Cosmological Constant) H2 ≡ ˙a a ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ 2 = 8π 3 ρ − k R2 − Λ 3
  4. 4. Cosmology Primer II   Hubble discovered the expansion of the Universe in 1929   Einstein dropped his cosmological constant   Next 70 years was the search for two numbers!   “Hubbles’ Constant”   Density of matter "0 # $0 $c = 8%G 3H0 2 $0 Distance from us RecessionVelocity Ω0 =1 for a flat universe
  5. 5. Distances and SNeIa n Thermonuclear explosions of White Dwarf stars White Dwarf accretes mass from or merges with a companion star, growing to a critical mass ~1.4Msun (Chandrasekhar) A violent explosion is triggered at or near the center, and the star is completely incinerated within seconds. In the core, light elements are burned in fusion reactions to produce ~0.6Msun Nickel. The radioactive decay of Nickel and Cobalt makes
  6. 6. Standardizable Candles A"er  correc(on,  σ~  0.16  mag   (~8%  distance  error)   Kim et al. 1997
  7. 7. Industrial Astronomy Sciama Building Only ~1 SNe per ~100 years in our Galaxy
  8. 8. SN Hubble Diagram (circa 1999) Sciama Building ICG only UK institute in SDSS-III a=1/(1+z) W € Ω0 = ΩM + ΩΛ € Ω0 = ΩM + ΩΛ
  9. 9. Nobel Prize 2011 "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae"
  10. 10. Baryon Acoustic Oscillations   Initial fluctuation in DM. Sound wave driven out by intense pressure at 0.57c. Initial fluctuation in DM. Sound wave driven out by intense pressure at 0.57c. Photons free stream, while baryons remain still as pressure is gone Today. Baryons and DM in equilibrium. The final configuration is the original peak at the center and an echo (the sound horizon) ~150Mpc in radius Illustrations by Martin White
  11. 11. Standard Rulers in the Sky WMAP 1st year data First year WMAP power spectrum 150Mpc
  12. 12. Flat Universe WMAP 1st year data “Ruler” is 150Mpc and distance to CMB is known to high accuracy (z=1089)
  13. 13. Today Densities known to ~10%
  14. 14. Energy of Nothingness! Coincidence problem? Log[a0/a(t)] € ρDE ~ a−3(1+w) € wi(z) ≡ pi ρi
  15. 15. Cosmological Constant € ρDE ~ a−3(1+w) (10120 too small)
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