What is our universe made of ? - PowerPoint PPT Presentation

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What is our universe made of ?

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  1. What is our universe made of ? fire , air, water, soil ! quintessence !

  2. Dark Energy dominates the Universe Energy - density in the Universe = Matter + Dark Energy 25 % + 75 %

  3. What is Dark Energy ?

  4. Composition of the universe Atoms : Ωb = 0.045 Dark Matter : Ωdm= 0.225 Dark Energy : Ωh = 0.73

  5. critical density • ρc =3 H² M² critical energy density of the universe ( M : reduced Planck-mass , H : Hubble parameter ) • Ωb=ρb/ρc fraction in baryons energy density in baryons over critical energy density

  6. Matter : Everything that clumps Abell 2255 Cluster ~300 Mpc

  7. Dark Matter Ωm = 0.23 total “matter” Most matter is dark ! So far tested only through gravity Every local mass concentration gravitational potential Orbits and velocities of stars and galaxies measurement of gravitational potential and therefore of local matter distribution

  8. Ωm= 0.27 gravitational lens , HST

  9. Gravitationslinse,HST

  10. Gravitationslinse,HST

  11. Gravitationslinse,HST

  12. Dark Matter in collision bullet cluster

  13. Matter : Everything that clumps Ωm= 0.27 Abell 2255 Cluster ~300 Mpc

  14. Dark Energy : Energy density that does not clump Photons , gravitons : insignificant

  15. spatially flat universe Ωtot = 1 • theory (inflationary universe ) Ωtot =1.0000……….x • observation ( WMAP ) Ωtot =1.02 (0.02)

  16. Picture of the big bang

  17. Anisotropy of background radiation:size of hot and cold spots

  18. Size of temperature fluctuationsin dependence on size of anisotropies ( angle ) contrast angle ca 10 degrees ca 1 degree

  19. Acoustic oscillations in plasma ca 10 degree ca 1 degree

  20. acoustic waves in the early Universe length compu- table

  21. Ωtot=1

  22. spatially flat Universe Ωtot = 1 Ωtot = 1 Ωtot=0.25

  23. WMAP 2006 Polarization

  24. Ωtot=1

  25. Dark Energy Ωm + X = 1 Ωm : 25% Ωh : 75% Dark Energy h : homogenous , often ΩΛ instead of Ωh

  26. Space between clumps is not empty :Dark Energy !

  27. Dark Energy : Homogeneously distributed

  28. Dark Energy density isthe same at every point of space “ homogeneous “No force in absence of matter –“ In what direction should it draw ? “

  29. Einstein’s equations :almost static Dark Energy predicts accelerated expansion of Universe

  30. Predictions for dark energy cosmologies The expansion of the Universe accelerates today !

  31. Structure formation : One primordial fluctuation spectrum CMB agrees with Galaxy distribution Lyman – α and Gravitational Lensing ! Waerbeke

  32. Power spectrum Baryon - Peak galaxy – correlation – function M.Tegmark + … Structure formation : One primordial fluctuation- spectrum SDSS

  33. Dark Energy :observations fit together !

  34. consistent cosmological model !

  35. Composition of the Universe Ωb = 0.045 visible clumping Ωdm= 0.2 invisibleclumping Ωh = 0.75 invisiblehomogeneous

  36. Dark Energy – a cosmic mystery

  37. What is Dark Energy ? Cosmological Constant or Quintessence ?

  38. Cosmological Constant- Einstein - • Constant λ compatible with all symmetries • No time variation in contribution to energy density • Why so small ? λ/M4 = 10-120 • Why important just today ?

  39. Energy density ρ ~ ( 2.4×10 -3 eV )- 4 Reduced Planck mass M=2.44×10 27 eV Newton’s constant GN=(8πM²) Cosmological mass scales Only ratios of mass scales are observable ! homogeneous dark energy: ρh/M4 = 6.5 10ˉ¹²¹ matter: ρm/M4= 3.5 10ˉ¹²¹

  40. Time evolution tˉ² matter dominated universe tˉ3/2 radiation dominated universe • ρm/M4 ~ aˉ³ ~ • ρr/M4 ~ aˉ4~ t -2radiation dominated universe Huge age small ratio Same explanation for small dark energy?

  41. Cosm. Const. | Quintessence static | dynamical

  42. Quintessence Dynamical dark energy , generated by scalarfield (cosmon) C.Wetterich,Nucl.Phys.B302(1988)668, 24.9.87 P.J.E.Peebles,B.Ratra,ApJ.Lett.325(1988)L17, 20.10.87

  43. Prediction : homogeneous dark energyinfluences recent cosmology- of same order as dark matter - Original models do not fit the present observations …. modifications

  44. Quintessence Cosmon – Field φ(x,y,z,t) similar to electric field , but no direction ( scalar field ) Homogeneous und isotropic Universe : φ(x,y,z,t)=φ(t) Potential und kinetic energy of the cosmon -field contribute to a dynamical energy density of the Universe !

  45. Cosmon • Scalar field changes its value even in the presentcosmological epoch • Potential und kinetic energy of cosmon contribute to the energy density of the Universe • Time - variable dark energy : ρh(t) decreases with time !

  46. Evolution of cosmon field Field equations Potential V(φ) determines details of the model V(φ) =M4 exp( - αφ/M ) for increasing φ the potential decreases towards zero !

  47. Cosmon • Tiny mass • mc ~ H (depends on time ! ) • New long - range interaction

  48. “Fundamental” Interactions Strong, electromagnetic, weak interactions On astronomical length scales: graviton + cosmon gravitation cosmodynamics

  49. observation will decide !