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Quintessence – Phenomenology

Quintessence – Phenomenology. How can quintessence be distinguished from a cosmological constant ?. Early dark energy. …predicted in models where dark energy is naturally of the same order as matter . Time dependence of dark energy. cosmological constant : Ω h ~ t² ~ (1+z) -3. M.Doran,….

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Quintessence – Phenomenology

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  1. Quintessence –Phenomenology

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

  3. Early dark energy

  4. …predicted in models where dark energy is naturally of the same order as matter

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

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

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

  8. Early quintessence slows down the growth of structure

  9. Growth of density fluctuations • Matter dominated universe with constantΩh : • Dark energy slows down structure formation Ωh < 10% during structure formation • Substantial increase of Ωh(t) since structure has formed! negative wh • Question “why now” is back ( in mild form ) P.Ferreira,M.Joyce

  10. Fluctuation spectrum Caldwell,Doran,Müller,Schäfer,…

  11. normalization of matter fluctuations rms density fluctuation averaged over 8h-1 Mpc spheres compare quintessence with cosmological constant Doran, Schwindt,…

  12. Early quintessence and growth of matter fluctuations early quintessence for small Ωh : ε/2 = 3/5

  13. for varying early dark energy : weighted average of Ω influence of late evolution of quintessence through conformal time τ0 and averaged equation of state atr : transition from slow early evolution of Ωh to more rapid late evolution

  14. at most a few percent dark energyin the early universe !

  15. effect of early quintessence presence of early dark energy decreases ρ for given t slower growth of perturbation

  16. 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

  17. Negative pressure • w < 0 Ωh increases (with decreasing z ) • w < -1/3 expansion of the Universe is accelerating • w = -1 cosmological constant late universe with small radiation component :

  18. small early and large presentdark energy • fraction in dark energy has substantially increased since end of structure formation • expansion of universe accelerates in present epoch

  19. exact relation between whand change in Ωh eq eq

  20. +(

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

  22. Quintessence becomes important “today”

  23. wh close to -1inferred from supernovae and WMAP

  24. Supernova cosmology Riess et al. 2004

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

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

  27. Supernova cosmology Riess et al. 2004

  28. supernovae :negative equation of state andrecent increase in fraction of dark energyare consistent !

  29. quintessence and CMB anisotropies influence by • early dark energy • present equation of state

  30. Anisotropy of cosmic background radiation Caldwell,Doran,Müller,Schäfer,…

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