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Growing Neutrinos as a solution of the why now problem of Dark Energy

Growing Neutrinos as a solution of the why now problem of Dark Energy. connection between dark energy and neutrino properties. = 1.27. present dark energy density given by neutrino mass. present equation of state given by neutrino mass !. Dark Energy and the Why now problem.

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Growing Neutrinos as a solution of the why now problem of Dark Energy

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  1. Growing Neutrinos as a solution of the why now problem of Dark Energy

  2. connection between dark energy and neutrino properties = 1.27 present dark energy density given by neutrino mass present equation of state given by neutrino mass !

  3. Dark Energyand theWhy now problem

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

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

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

  7. 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 ?

  8. Cosm. Const | Quintessence static | dynamical

  9. Why now problem • Why is dark energy important now and not in the past ?

  10. 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

  11. connection between dark energy and neutrino properties = 1.27 present dark energy density given by neutrino mass Energy density : ρ1/4 ~ 2.4×10 -3 eV

  12. neutrino masses anddark energy densitydepend on time !

  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. 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 ! V(φ) =M4 exp( - αφ/M )

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

  18. 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 !

  19. 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

  20. exponential potentialconstant fraction in dark energy can explain order of magnitude of dark energy ! Ωh = 3(4)/α2

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

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

  23. cosmic coincidence

  24. coincidence problem What is responsible for increase of Ωh for z < 6 ? Why now ?

  25. A new role forneutrinos in cosmology ?

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

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

  28. cosmon evolution “stopped” scaling

  29. stopped scalar fieldmimicks acosmological constant( almost …) rough approximation for dark energy : • before redshift 5-6 : scaling ( dynamical ) • after redshift 5-6 : almost static ( cosmological constant )

  30. cosmon coupling to neutrinos basic ingredient :

  31. Cosmon coupling to neutrinos • can be large ! • 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 Fardon,Nelson,Weiner L.Amendola,M.Baldi,…

  32. growing neutrinos

  33. 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 • cosmon plays crucial role

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

  35. connection between dark energy and neutrino properties = 1.27 present dark energy density given by neutrino mass present equation of state given by neutrino mass !

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

  37. varying neutrino – cosmon coupling • specific model • can naturally explain why neutrino – cosmon coupling is much larger than atom – cosmon coupling

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

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

  40. cascade

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

  42. cascade mechanism triplet expectation value ~

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

  44. strong effective neutrino – cosmon coupling for φ → φt typical present value : β≈ 50 cosmon mediated attraction between neutrinos is about 502 stronger than gravitational attraction

  45. crossover fromearly scaling solution to effective cosmological constant

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

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

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

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

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

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