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Agegraphic Dark Energy

Agegraphic Dark Energy. Hao Wei Department of Physics and Tsinghua Center for Astrophysics, Tsinghua University (in collaboration with Prof. Rong-Gen Cai). “String Theory and Cosmology” program. KITPC 12 Oct 2007. Karolyhazy relation.

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Agegraphic Dark Energy

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  1. Agegraphic Dark Energy Hao Wei Department of Physics and Tsinghua Center for Astrophysics, Tsinghua University (in collaboration with Prof. Rong-Gen Cai) “String Theory and Cosmology” program KITPC 12 Oct 2007

  2. Karolyhazy relation • Before a completely successful quantum theory of gravity is available, it is more realistic to combine the quantum mechanics with general relativity directly. • Following the line of quantum fluctuations of spacetime, Karolyhazy et al. (1966) made an interesting observation concerning the distance measurement for Minkowski spacetime through a light-clock Gedanken experiment

  3. The distance t in Minkowski spacetime cannot be known to a better accuracy than Karolyhazy, Nuovo Cim. A 42, 390 (1966); Maziashvili, gr-qc/0612110; arXiv:0705.0924 [gr-qc]; Sasakura, Prog. Theor. Phys. 102, 169 (1999) [hep-th/9903146]; Ng and Van Dam, Mod. Phys. Lett. A 9, 335 (1994); ibid 10, 2801 (1995); Ng, gr-qc/0703096 and more ……

  4. The Karolyhazy relation together with the time-energy uncertainty relation enables one to estimate a quantum energy density of the metric fluctuations of Minkowski spacetime. The energy density of metric fluctuations of Minkowski spacetime is given by See Maziashvili, arXiv:0708.1472 [hep-th] for three different approaches to all above results

  5. The Original Version of the Agegraphic Dark Energy Cai, arXiv:0707.4049 [hep-th], Phys. Lett. B in press As the most natural choice, the time scale in the Karolyhazy relation is chosen to be the age of the universe So, the energy density of the agegraphic dark energy is given by

  6. We consider a flat FRW universe with agegraphic dark energy and pressureless matter, the Friedmann equation reads The fractional energy density It is easy to get The EoS of the agegraphic DE n > 1 is necessary to drive the (present) accelerated expansion of our universe (see e.g. Wei & Cai, arXiv:0707.4052 for details)

  7. Including Interactions Wei & Cai, arXiv:0707.4052 [hep-th] We assume that the agegraphic dark energy and pressureless (dark) matter exchange energy through interaction term Q and so on

  8. Statefinder Diagnostic and w − w′Analysis Wei & Cai, Phys. Lett. B655 (2007) 1-6 [arXiv:0707.4526] The so-called statefinder pair {r, s}

  9. Agegraphic DE without Interaction

  10. Agegraphic DE with Interaction

  11. Observational Constraints on Agegraphic Dark Energy Wu, Zhang, Li, Cai, Zhu, arXiv:0708.0349 [astro-ph] The original agegraphic DE was constrained by using the observations of SNe Ia, shift parameter R and BAO of Large Scale Structure

  12. The advantages and disadvantages of agegraphic DE • The Karolyhazy relation naturally obeys the holographic black hole entropy bound • By choosing the age of the universe rather than the future event horizon as the length measure, the drawback concerning causality in the holographic dark energy model does not exist in the agegraphic dark energy model

  13. However … We thank Prof. Miao Li for pointing out this confusion In the matter-dominated epoch On the other hand, a~t2/3, T2~a3, so Confliction ! Since In fact, the agegraphic dark energy tracks the dominated components. The agegraphic dark energy never dominates

  14. Two Solutions See Cai, arXiv:0707.4049 v2 & v4; Wei & Cai, arXiv:0708.0884

  15. A New Model of Agegraphic Dark Energy Wei & Cai, arXiv:0708.0884 [astro-ph] We choose the time scale to be the conformal time instead

  16. At first, we consider a flat FRW universe containing the new agegraphic dark energy and pressureless matter

  17. Thanks to its special analytic features in the radiation-dominated and matter-dominated epochs, NADE is actually a single-parameter model. If the single model parameter n is given, all other physical quantities of NADE are determined correspondingly. The coincidence problem can be solved naturally in the NADE model provided that n is of order unity. See Wei & Cai, arXiv:0708.1894 [astro-ph] for details.

  18. Including Interactions

  19. Cosmological Constraints on New Agegraphic Dark Energy Wei & Cai, arXiv:0708.1894 [astro-ph]

  20. Thanks! KITPC, Beijing, 12 Oct 2007 Blessed be the Lord, who daily loadeth us with benefits, even the God of our salvation. (Psalms 68:19)

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