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Dunkle Energie – Ein kosmisches Raetsel

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Dunkle Energie – Ein kosmisches Raetsel

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  1. Dark Energy- a cosmic mystery Dunkle Energie – Ein kosmisches Raetsel

  2. Dark Energy –a cosmic mystery C.Wetterich A.Hebecker,M.Doran,M.Lilley,J.Schwindt, C.Müller,G.Schäfer,E.Thommes, R.Caldwell

  3. What is our Universemade of ?

  4. Quintessence ! fire , air, water, soil !

  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. Composition of the universe Ωb = 0.045 Ωdm= 0.225 Ωh = 0.73

  7. baryons dust Ωb=0.045 only 5 percent of our universe consist of known matter ! SDSS ~60,000 of >300,000 galaxies

  8. Abell 2255 Cluster ~300 Mpc

  9. Ωb=0.045 from nucleosynthesis, cosmic background radiation

  10. Dark Matter Ωm = 0.27 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

  11. Gravitationslinsen gravitational lens , HST

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

  13. picture of the big bang

  14. Wilkinson Microwave Anisotropy Probe A partnership between NASA/GSFC and Princeton Science Team: NASA/GSFC Chuck Bennett (PI) Michael Greason Bob Hill Gary Hinshaw Al Kogut Michele Limon Nils Odegard Janet Weiland Ed Wollack Brown Greg Tucker UCLA Ned Wright Princeton Chris Barnes Norm Jarosik Eiichiro Komatsu Michael Nolta Chicago Stephan Meyer UBC Mark Halpern Lyman Page Hiranya Peiris David Spergel Licia Verde

  15. mean values Ωtot =1.02 Ωm =0.27 Ωb =0.045 Ωdm =0.225

  16. Ωtot=1

  17. Dark Energy Ωm + X = 1 Ωm : 30% Ωh : 70% Dark Energy h : homogenous , often ΩΛ instead of Ωh

  18. Dark Energy : homogeneously distributed

  19. Dark Energy : prediction: The expansion of the Universe accelerates today !

  20. Perlmutter 2003

  21. Supernova cosmology Riess et al. 2004

  22. Dark energy and SN ΩM = 0.29 +0.05-0.03 (SN alone, for Ωtot=1)

  23. Structure formation Structures in the Universe grow from tiny fluctuations in density distribution stars , galaxies, clusters One primordial fluctuation spectrum describes all correlation functions !

  24. Structure formation : fluctuation spectrum CMB agrees with galaxy distribution Lyman – α forest and gravitational lensing effect ! Waerbeke

  25. consistent cosmological model !

  26. Composition of the Universe Ωb = 0.045 visible clumping Ωdm= 0.225 invisibleclumping Ωh = 0.73 invisiblehomogeneous

  27. Dark Energy- a cosmic mystery Dunkle Energie – Ein kosmisches Raetsel

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

  29. Cosmological Constant • 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 ?

  30. Cosm. Const. | Quintessence static | dynamical

  31. Energy density ρ ~ ( 2.4×10 -3 eV )- 4 Reduced Planck mass M=2.44×1018GeV 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

  32. 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?

  33. Quintessence Dynamical dark energy , generated by scalar field (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

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

  35. Cosmon • Tiny mass • mc ~ H • New long - range interaction

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

  37. Evolution of cosmon field Field equation Potential V(φ) determines details of the model e.g. V(φ) =M4 exp( - φ/M ) for increasing φ the potential decreases towards zero

  38. Cosmological equations

  39. Cosmic Attractors Solutions independent of initial conditions typically V~t -2 φ ~ ln ( t ) Ωh ~ const. details depend on V(φ) or kinetic term early cosmology

  40. Dynamics of quintessence • Cosmonj: scalar singlet field • Lagrange density L = V + ½ k(φ)¶j ¶j (units: reduced Planck mass M=1) • Potential : V=exp[-j] • “Natural initial value” in Planck era j=0 • today: j=276

  41. Quintessencemodels • Kinetic function k(φ) : parameterizes the details of the model - “kinetial” • k(φ) = k=const. Exponential Q. • k(φ ) = exp ((φ – φ1)/α) Inverse power law Q. • k²(φ )= “1/(2E(φc – φ))” Crossover Q. • Naturalness criterion: k(φ=0)/ k(φtoday) : not tiny or huge ! - else: explanation needed -

  42. Quintessence becomes important “today”

  43. Equation of state p=T-V pressure kinetic energy ρ=T+V energy density Equation of state Depends on specific evolution of the scalar field

  44. Negative pressure • w < 0 Ωh increases • w < -1/3 expansion of the Universe is accelerating • w = -1 cosmological constant

  45. Quintessence becomes important “today”

  46. SN and equation of state Riess et al. 2004

  47. How can quintessence be distinguished from a cosmological constant ?

  48. Time dependence of dark energy cosmological constant : Ωh ~ t² ~ (1+z)-3 M.Doran,…

  49. Early dark energy A few percent in the early Universe Not possible for a cosmological constant