Growing neutrinos and cosmological selection

1. Growing neutrinos and cosmological selection

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

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 25 % + 75 %

5. Ωm= 0.25 gravitational lens , HST

6. Ωtot=1

7. Matter : everything that clumps--------------------Dark Energy density isthe same at every point of space “ homogeneous “Space between clumps is not empty

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

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

10. 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 ?

11. Cosm. Const. | Quintessence static | dynamical

12. 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

13. 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?

14. 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

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

16. Quintessence Cosmon – Field φ(x,y,z,t) 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 !

17. 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 !

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

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

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

21. 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

22. exponential potentialconstant fraction in dark energy can explain order of magnitude of dark energy ! Ωh = n/α2

23. realistic quintessence fraction in dark energy has to increase in “recent time” !

24. cosmic coincidence

25. Quintessence becomes important “today” No reason why w should be constant in time !

26. coincidence problem What is responsible for increase of Ωh for z < 6 ?

27. Early quintessence Ωh changes only modestly w changes in time transition special feature in cosmon potential or kinetic term becomes important “now” tuning at ‰ level Late quintessence w close to -1 Ωh negligible in early cosmology needs tiny parameter, similar to cosmological constant a) Properties of cosmon potential or kinetic term

28. Onset of matter dominance K- essence Amendariz-Picon, Mukhanov, Steinhardt needs higher derivative kinetic term Appearance of non-linear structure Back-reaction effect needs coupling between Dark Matter and Dark Energy b) Quintessence reacts to some special event in cosmology

29. growing neutrino mass triggers transition to almost static dark energy growing neutrino mass L.Amendola,M.Baldi,…

30. connection between dark energy and neutrino properties present dark energy density given by neutrino mass present equation of state given by neutrino mass !

31. dark energy fraction determined by neutrino mass constant neutrino - cosmon coupling β variable neutrino - cosmon coupling

32. cosmon coupling to neutrinos basic ingredient :

33. Cosmon coupling to atoms • Tiny !!! • Substantially weaker than gravity. • Non-universal couplings bounded by tests of equivalence principle. • Universal coupling bounded by tests of Brans-Dicke parameter ω in solar system. • Only very small influence on cosmology.

34. Cosmon coupling to Dark Matter • Only bounded by cosmology • Substantial coupling possible • Can modify scaling solution and late cosmology • Role in clustering of extended objects ? L. Amendola

35. Cosmon coupling to neutrinos • can be large ! Fardon,Nelson,Weiner • interesting effects for cosmology if neutrino mass is growing • growing neutrinos can stop the evolution of the cosmon • transition from early scaling solution to cosmological constant dominated cosmology L.Amendola,M.Baldi,…

36. growing neutrino mass triggers transition to almost static dark energy growing neutrino mass

37. cosmological selection • present value of dark energy density set by cosmological event ( neutrinos become non – relativistic ) • not given by ground state properties !

38. growing neutrinos

39. end of matter domination • growing mass of neutrinos • at some moment energy density of neutrinos becomes more important than energy density of dark matter • end of matter dominated period • similar to transition from radiation domination to matter domination • this transition happens in the recent past

40. neutrino mass seesaw and cascade mechanism triplet expectation value ~ doublet squared omit generation structure

41. cascade mechanism triplet expectation value ~ M.Magg , … G.Lazarides , Q.Shafi , …

42. varying neutrino mass ε≈ -0.05 triplet mass depends on cosmon field φ neutrino mass depends on φ

43. singular neutrino mass triplet mass vanishes for φ → φt neutrino mass diverges for φ → φt

44. early scaling solution ( tracker solution ) neutrino mass unimportant in early cosmology

45. growing neutrinos change cosmon evolution modification of conservation equation for neutrinos

46. effective stop of cosmon evolution cosmon evolution almost stops once • neutrinos get non –relativistic • ß gets large This always happens for φ → φt !

47. effective cosmological triggerfor stop of cosmon evolution :neutrinos get non-relativistic • this has happened recently ! • sets scales for dark energy !

48. effective cosmological constantat late time realistic value for αφt / M ≈ 276

49. crossover to dark energy dominated universe starts at time when “neutrino force” becomes important for the evolution of the cosmon field

50. cosmological selection !