1 / 107

Understanding Dark Energy: The Cosmic Mystery of Quintessence

This comprehensive exploration delves into the enigmatic nature of dark energy, which comprises approximately 70% of the universe and drives its accelerated expansion. We discuss the classification of dark energy, including the cosmological constant and quintessence, and the implications of various energy densities (Ωb, Ωdm, and Ωh) in cosmology. Drawing from observations and theoretical frameworks, this work aims to unravel the complexities of the universe's composition, presenting insights into its gravitational interactions and the structure formation through primordial fluctuations.

arne
Télécharger la présentation

Understanding Dark Energy: The Cosmic Mystery of Quintessence

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Dark Energy – a cosmic mystery

  2. Quintessence C.Wetterich A.Hebecker, M.Doran, M.Lilley, J.Schwindt, C.Müller, G.Schäfer, E.Thommes, R.Caldwell, M.Bartelmann, K.Kharwan, G.Robbers, T.Dent, S.Steffen, L.Amendola, M.Baldi , N.Brouzakis , N.Tetradis, D.Mota, V.Pettorino, T.Krüger, M.Neubert

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

  4. Dark Energy dominates the Universe Energy - density in the Universe = Matter + Dark Energy 1/4 + 3/4

  5. What is Dark Energy ?

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

  7. 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

  8. Baryons/Atoms Dust Ωb=0.045 Only 5 percent of our Universe consist of known matter ! SDSS

  9. Abell 2255 Cluster ~300 Mpc

  10. Ωb=0.045 from nucleosynthesis, cosmic background radiation

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

  12. 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

  13. Ωm= 0.27 gravitational lens , HST

  14. Gravitationslinse,HST

  15. dark matter distribution in the Universe HST

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

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

  18. picture of the big bang

  19. Mean values WMAP 2003 Ωtot =1.02 Ωm =0.27 Ωb =0.045 Ωdm =0.225

  20. Ωtot=1

  21. Ωtot=1

  22. WMAP 2006 Polarization

  23. Dark Energy Ωm + X = 1 Ωm : 1/4 Ωh : 3/4 Dark Energy h : homogenous , often ΩΛ instead of Ωh

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

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

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

  27. dark energy and accelerated expansion second important property of dark energy: increase of Ωh causes accelerated expansion of the Universe change from deceleration to acceleration a few billion years ago

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

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

  30. consistent cosmological model !

  31. Composition of the Universe Ωb = 0.045 visible clumping Ωdm= 0.22 invisibleclumping Ωh = 0.73 invisiblehomogeneous

  32. Dark Energy – a cosmic mystery

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

  34. 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 ?

  35. cosmological constant • poorly understood • naïve arguments on natural size based on estimate of quantum fluctuations often miss possible crucial symmetries or fixed point behavior • anthropic principle : a sophisticated way to say that we do not know – or a theory has no explanation …

  36. Dynamical or staticdark energy ?

  37. Cosm. Const. | Quintessence static | dynamical

  38. 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

  39. 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?

  40. 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

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

  42. 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 and homogenous energy density of the Universe !

  43. 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 !

  44. 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 !

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

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

  47. cosmon : “the Higgs particle of dynamical dark energy” may be an effective or composite field , e.g. in certain modified gravity theories appears as quintessence field, chameleon, …and with many other names

  48. Dynamical or staticdark energy ?

More Related