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COSMIC ACCELERATION Dark energy and modified theories

COSMIC ACCELERATION Dark energy and modified theories. M. SAMI Centre for Theoretical Physics Jamia Millia University New Delhi. Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya. REFERENCES.

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COSMIC ACCELERATION Dark energy and modified theories

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  1. COSMIC ACCELERATIONDark energy and modified theories M. SAMI Centre for Theoretical Physics Jamia Millia University New Delhi Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya . NTHU 2012

  2. REFERENCES • MS, “ A primer on problems and prospects of dark energy “ Curr Sci, V 97, 848 (2009) [arXiv:0904.3445]. • M. Turner, D. Huterer, “Cosmic Acceleration, Dark Energy and Fundamental Physics“J.Phys.Soc.Jap.76:111015,2007. • E. Copeland, MS, S. Tsujikawa, “ Dynamic of Dark Energy”, hep-th/0603057. • Zeldovic and Novikov, Structure and evolution of universe, V 2 NTHU 2012

  3. BRIEF OVER VIEW Late time inconsistency of hot big bang: Resolution of age crisis—cosmological constant. Theoretical issues related cosmological constant (Sakharov) Coincidence ; Fine tuning. Quintessence and its problems. Modified theories of gravity: Local physics---Screening mechanisms. Chameleon, Symmetron , Vainshtein mechanism. Scope of chameleon/symmetron : Self acceleration. Non-linear massive gravity NTHU 2012

  4. Inconsistencies of standard model EARLY TIMES: Flatness problem Primordial inhomogeneities INFLATION Horizon problem LATE TIMES: Age crisis NTHU 2012

  5. AGE CRISIS IN HOT BIG BANG Matter dominated universe: NTHU 2012

  6. AGE CRISIS IN HOT BIG BANG Let us ignore gravity for a moment : Present epoch: NTHU 2012

  7. AGE CRISIS :Repulsive effect Cosmological constant or Hook’s law Static universe Neumann (1895) and Seeliger(1896) Einstein 1917 If no quasi-static universe then away with cosmological constant! MS, arXiv: 0904.3445 NTHU 2012

  8. AGE CRISIS AND ITS RESOLUTION WITH Open universe (K<0) Repulsive effect NTHU 2012

  9. AGE CRISIS AND ITS RESOLUTION WITH NTHU 2012

  10. ENERGY OF VACUUM SAKHAROV 1968 NTHU 2012

  11. The effective Cosmological constant NTHU 2012

  12. COSMOLOGICAL CONSTANTWrong formulation Old cosmological constant problem New cosmological constant problem NTHU 2012

  13. The correct level of fine tuning NTHU 2012

  14. String Landscape We are there! NTHU 2012

  15. FINE TUNING PROBLEM : TWO DISTANT SCALES TOGETHER THE BIG AND THE SMALL PUTTING THEM TOGETHER NTHU 2012

  16. CINCIDENCE PROBLEM: SHAME NTHU 2012

  17. WHERE IS THE COINSIDENCE ? z NTHU 2012

  18. SCALAR FIELD AS DARK ENERGYQuintessence for steep pot. Predictive power of scalar fields For a priori given cosmic history, it is always possible to construct a field potential such that it gives rise to the desired result. Thus the scalar field models should be judged by their generic features. NTHU 2012

  19. Scalar Field Dynamics in presence of background matter : Tracker or Freezing Models Scaling Solution: MS, Curr Sci, V 97, 848 (2009) [arXiv:0904.3445] NTHU 2012 Int.J.Mod.Phys.D15:1753-1936,2006, E.Copeland, MS, S Tsujikawa.

  20. Absence of trackers: Thawing Models NTHU 2012

  21. Trackers and non-trackers • Trackers (Freezing models): Potentials which mimic steep exponential • at early epochs and become shallow at late times. Thawing models:Most of the systems belong to this category , Scaling Pot. Phantom field: A. Sen, HEP0204:048,2002 N Mazumdar, S. Panda, A. Perez-Lorenzana, Phys.. B614,101(2001) E.Copeland, M. Garousi, MS, S. Tsujikawa PRD71:043003,2005, S. Tsijikawa, MS, PRD71:043003,2005 . NTHU 2012

  22. Quintessence problem C. Kolda and D Lyth, hep-th.9811375 Unstable under radiative corrections when coupled to other fields unless severely fine tuned. NTHU 2012

  23. MODIFIED THEORIES OF GRAVITY LARGE SCALE MODIFICATION • Chameleon theories. • Galileon modified theories • Massive gravity • Scalar degree(s) of freedom Requirements • Local physics be intact • Cosmic acceleration NTHU 2012

  24. SCALARON: Requirements DE: Solar Physics: NTHU 2012

  25. Chameleon Field NTHU 2012

  26. MASS SCREENING OR FIFTH FORCE SUPPRESSION (Basic Idea) Localized source: Chameleon or Symmetron NTHU 2012

  27. Kinetic suppression NTHU 2012

  28. Chameleon versus Galileon(Vainshtein ) Chameleon Galileon Small distances: Large distances: NTHU 2012

  29. Chameleon at work R, M NTHU 2012

  30. Vainstein Effect- dynamical suppression of fifth force Short distances: Large distances: NTHU 2012

  31. Vainshtein at work R, M NTHU 2012

  32. Symmetron: Dark energy NTHU 2012

  33. Symmetron: Dark energy Symmetry should break: Local gravity constraints NTHU 2012

  34. Scalar tensor theories -Einstein frame -Jordon frame NTHU 2012

  35. Local gravity constraints: Screening Mechanism Chameleon Field NTHU 2012

  36. VIABLE f(R) MODELS Stability conditions: Stable de Sitter: Local gravity constraints: NTHU 2012

  37. Problems of f(R): scalaron mass Thongkool, MS, R. Gannouji, S.Jhingan, Phys.Rev.D80:043523,2009 ; NTHU 2012

  38. CURING THE SINGULARITY ? Countering Term: Thongkool, MS, S. Rai Choudhury, arXiv:0908.1663 Thongkool, MS, R. Gannouji, S. Jhingan, Phys.Rev.D80:043523,2009 ; S A. Appleby,R. A. Battye, A. Starobinsky, arXiv:0909.1737 arXiv: 1201.4546, Chung-Chi Lee, Chao-Qiang Geng, Louis Yang NTHU 2012

  39. SELF ACCELERATION:SCOPE OF CHAMELEON THEORIES Self acceleration: Screening: NTHU 2012

  40. Chameleon/Symmetron theories- No scope for self acceleration arXiv:1284612: J. Wang, L. Hui and J. Khoury arXiv: 1211.2289: K. Bamba, R. Gannouji, MS NTHU 2012

  41. Glimpses of massive gravity (helicity 2 object) + (helicity 1 object)+ (helicity zero object) Universally couples to all fields a b Ghost: Stuckelberging NTHU 2012

  42. Best model for quintessential inflation BEST MODEL OF INFLATION AND DARK ENERGY? NTHU 2012

  43. NATURE OF DARK ENERGY IT COULD BE ANYTHING OR IT COULD BE NOTHING NTHU 2012

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