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Zhu, Zong-Hong Dept. of Astron., Beijing Normal University, Beijing 100875, China

This workshop focuses on the study of dark energy and its impact on the universe using observational data. It explores various dark energy models and proposes new theories to explain its properties. The workshop also discusses the observational constraints on dark energy from supernovae, cosmic microwave background, large-scale structure, and other astronomical data.

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Zhu, Zong-Hong Dept. of Astron., Beijing Normal University, Beijing 100875, China

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  1. Observational Constraints on Dark Energy Zhu, Zong-Hong Dept. of Astron., Beijing Normal University, Beijing 100875, China zhuzh@bnu.edu.cn

  2. Breakthrough of 1998: the Winner ASTRONOMY: Cosmic Motion Revealed the 2nd Sino-French Workshop

  3. Breakthrough of 2003: the Winner Illuminating the Dark Universe the 2nd Sino-French Workshop

  4. 0 How to accelerate the Universe? • General Relativity: 3P PDE < 0 ! the 2nd Sino-French Workshop

  5. Cosmological constant problem Fine tuning the 2nd Sino-French Workshop

  6. Cosmological constant problem log r radiation (~1/a4) Coincidence matter (~1/a3) cosmological constant (~constant) log a radiation dominated matter dominated Lambda dominated imagination dominated the 2nd Sino-French Workshop

  7. Beyond Einstein: 3 question marks What powered the Big Bang? What happans at the edge of a black hole? What is dark energy? the 2nd Sino-French Workshop

  8. A NNSFC Project: study on cosmic dark energy • Beijing Normal University (Z.-H. Zhugroup) • Institute of High Energy Physics, CAS(X. Zhang group) • National Astronomical Observatories, CAS (X. Chen group) • Peking University (Z. Fan group) the 2nd Sino-French Workshop

  9. A NNSFC Project: study on cosmic dark energy • Theoretical Models of Dark Energy • Testing DE Models with Astronomical Data • LaMOST Project and Dark Energy (Prof. Y. Zhao’s talk) • Chinese Future Astronomical Instruments for Dark Energy Probe (Prof. X. Chen & X. Wu’s talks for 21CMA; C.-J. Jin’s talk for FAST) the 2nd Sino-French Workshop

  10. Dark Energy Models: classification Observation Data Theoretical Assumptions General Relativity Cosmo Principle ModelI Model II Model III the 2nd Sino-French Workshop

  11. Dark Energy Models: our proposals:motivation w seems to cross -1 Huterer & Cooray,PRD, 71 (2005) 023506, astro-ph/0404062 the 2nd Sino-French Workshop

  12. Dark Energy Models: our proposals:quintom If the running of w(z), especially a transition across –1, confirmed in the future, big challenge to the model building * Vacuum : w=-1 * Quintessence: w>-1 * Phantom: w<-1 * K-essence: w>-1 or w<-1 but cannot across -1 A new scenario of Dark Energy : Quintom (Zhang et al.astro-ph/0404224) the 2nd Sino-French Workshop

  13. Dark Energy Models: our proposals:quintom Quintom Model building: Why challenges? No-Go Theorem: Equation of State w can not cross over -1 if the following conditions are satisfied: Bo Feng et al. astro-ph/0404224 Vikman Phys. Rev. D 71, 023515 (2005) • Einstein Gravity • Minimal Coupling • Single Scalar Field • Without higher derivative Gong-Bo Zhao et al. astro-ph/0507482 ……. Hao Wei, PhD thesis Examples of Quintom-like Models: 1. two scalar field 2. single scalar field with higher derivative 3. including vector field …… 4. Nonminimal Coupling …….. the 2nd Sino-French Workshop

  14. Detailed study on: Two-field models of Quintom Dark Energy -Xiao-fei Zhang ,Hong Li, Yunsong Piao and Xinmin Zhang I.Quintom model with two scalar fields: II. Quintom model with Phantom field and neutrino: Astro-ph/0501652

  15. Dark Energy Models: our proposals:interacting Chaplygin gas The continuity equation of the interaction system, Note that they are independent of general relativity, or any other gravity theories. H. Zhang & Z.-H. Zhu, PRD, 73 (2006) 043518,astro-ph/0509895 the 2nd Sino-French Workshop

  16. Dark Energy Models:our proposals:Unruh radiation H. Zhang & Z.-H. Zhu,astro-ph/0607531 See Dr. H. Zhang’s Talk the 2nd Sino-French Workshop

  17. Observational Constraints: w from SN, SDSS, WMAP Jun-Qing Xia, Gong-Bo Zhao, Bo Feng, Hong Li and Xinmin Zhang Phys.Rev.D73, 063521, 2006 the 2nd Sino-French Workshop

  18. Observational Constraints: on Modified Friedmann Equation (MFE) Cosmology • Standard Friedmann equation (=0, =0) • Modified Friedman equation (Freese & Lewis 2002) the 2nd Sino-French Workshop

  19. Observational Constraints:on MFE Cosmology Summary • Constraints from angular size-redshift data • Zhu & Fujimoto 2002, ApJ, 581, 1 • Constraints from SNeIa • Zhu & Fujimoto 2003, ApJ, 585, 52 • Wang, Freese, Gondolo & Lewis 2003, ApJ, 594, 25 • Constraints from CMB (WMAP) • Sen & Sen 2003a, ApJ, 588, 1; 2003b, PRD, 68, 023513 • Constraints from large-scale structure • Multamaki, Gaztanaga & Manera 2003, MNRAS, 344, 761 • Constraints from turnaround redshift of cosmic expansion • Zhu & Fujimoto 2004, ApJ, 602, 12 • Constraints from SNeIa and X-ray mass fraction of clusters • Zhu, Fujimoto & He 2004, ApJ, 603, 365 the 2nd Sino-French Workshop

  20. Observational Constraints:on MFE Cosmology Parameters of MFE cosmology • (B,n), (zeq,n) or (m,n) • Hubble Parameter as Function of z,H=H0E(z) • The Critical/Matter Density the 2nd Sino-French Workshop

  21. Observational Constraints:on MFE Cosmology From SNeIa and Fanaroff-Riley type IIb radio galaxies • Dimensionless coordinate distance data taken from Daly & Djorgovski 2003, ApJ, 597, 9 • 78 SNeIa from Perlmutter et al. (1999), Riess et al. (1998,2001). • 20 FRIIb radio galaxies from Daly & Guerra (2002). Z.-H. Zhu et al. 2004, ApJ, 603,365 the 2nd Sino-French Workshop

  22. Observational Constraints:on MFE Cosmology From SNeIa and Fanaroff-Riley type IIb radio galaxies • A 2 minimization method is used to determine (m,n). • The best fit happans at (m,n)=(0.38,-0.20). • The 68.3% and 95.4% confidence level in the (m,n) plane are shown. Z.-H. Zhu et al. 2004, ApJ, 603,365 the 2nd Sino-French Workshop

  23. Galaxy Clusters as a Probe for Cosmology SZ+X-ray  angular diameter distance Strong Lesning Weak Lensing the 2nd Sino-French Workshop

  24. Galaxy Clusters as a Probe for Cosmology Gas mass fraction in clusters of galaxies assume the gas mass fraction fgas(z) invariant  constraints on cosmology (dA(z) – z relation) the 2nd Sino-French Workshop

  25. fgas of galaxy clustres as a cosmological probe Allen et al. 2002, 2003 the 2nd Sino-French Workshop

  26. Observational Constraints:on MFE Cosmology From X-ray gas mass fraction of clusters • fgas data are taken from Allen et al. (2002,2003). • fgas~[DA]3/2 when infered from X-ray observations. Generally DASCDM with h=0.5 is used. • The “true” cosmology should be the one making these measured fgas,oi to be invariant with redshift. Z.-H. Zhu et al. 2004, ApJ, 603,365 the 2nd Sino-French Workshop

  27. Observational Constraints:on MFE Cosmology From X-ray gas mass fraction of clusters • A 2 minimization method is used to determine (m,n). • Marginalize over b=0.0205 0.0018 from QSO HS 0105+ 1619 (O’Meara et al. 2001), b=0.93  0.05 from simulations (Bialek et al. 2001) and h=0.72  0.08 from Hubble Key Project (Freedman et al. 2001) • The best fit happans at (m,n)= (0.30,0.14). Z.-H. Zhu et al. 2004, ApJ, 603,365 the 2nd Sino-French Workshop

  28. Observational Constraints:on MFE Cosmology From combination analysis of the databases 12(m,n)= 22(m,n)= T2(m,n)= 12(m,n)+ 22(m,n) Z.-H. Zhu et al. 2004, ApJ, 603,365 the 2nd Sino-French Workshop

  29. Observational Constraints:on MFE Cosmology From combination analysis of the databases • At the 95.4% confidence level, m=0.30  0.02, n=0.06+0.32-0.28. • The universe switches from deceleration to acceleration around redshift of (0.52, 0.73). • The modified term in MFE dominates around redshift of (0.25, 0.55). Z.-H. Zhu et al. 2004, ApJ, 603,365 the 2nd Sino-French Workshop

  30. Observational Constraints:on MFE Cosmology From turnaround redshift zq=0 • zq=0 depends on both of m and n. (see eq. below) • For each m, there exists one npeak(m), which leads to a maximum of zq=0. • Higher m is, lower zq=0 is. • For each zq=0, there exists an upper limit for m, e.g., zq=0>0.6, then m<0.328. the 2nd Sino-French Workshop

  31. Observational Constraints:on MFE Cosmology From turnaround redshift zq=0 : equations the 2nd Sino-French Workshop

  32. Observational Constraints:on MFE Cosmology From turnaround redshift zq=0 • The thick solid line is zq=0=0. • The cross-hatched area is the present optimistic m=0.330  0.035. • The dashed lines are m=0.2 and 0.4 respectively. • The shaded area gives 0.6 < zq=0 <1.7. Z.-H. Zhu et al. 2004, ApJ, 602, 12 the 2nd Sino-French Workshop

  33. A Brane World Model (BWM): DGP • A self-accelerating 5-dimensional BWM • With a noncompact, infinite volume extra dimension • An ordinary 5-dimensional Einstein-Hilbert action • A 4-dimensional Ricci scalar term induced on the brane Dvali, Gabadadze & Porrati 2000 the 2nd Sino-French Workshop

  34. Observational Constraints:on DGP Model Z.-H. Zhu et al. 2005 ApJ 620,7 the 2nd Sino-French Workshop

  35. Observational Constraints:on DGP Model Zhu & Alcaniz 2005 ApJ 620,7 the 2nd Sino-French Workshop

  36. Observational Constraints:on DGP Model Zhu & Alcaniz 2005 ApJ 620,7 the 2nd Sino-French Workshop

  37. Observational Constraints:on DGP Model Z.-K. Guo & Z.-H. Zhu et al. 2006, ApJ, 646, 1 the 2nd Sino-French Workshop

  38. Observational Constraints:on DGP Model (m, rc)=(0.272,0.211) Z.-K. Guo & Z.-H. Zhu et al. 2006, ApJ, 646, 1 the 2nd Sino-French Workshop

  39. Observational Constraints:on DGP Model (m, rc)=(0.265,0.216) Z.-K. Guo & Z.-H. Zhu et al. 2006, ApJ, 646, 1 the 2nd Sino-French Workshop

  40. Observational Constraints:on DGP Model Z.-K. Guo & Z.-H. Zhu et al. 2006, ApJ, 646, 1 the 2nd Sino-French Workshop

  41. Observational Constraints:on DGP Model Z.-K. Guo & Z.-H. Zhu et al. 2006, ApJ, 646, 1 the 2nd Sino-French Workshop

  42. Observational Constraints:on DGP Model Z.-K. Guo & Z.-H. Zhu et al. 2006, ApJ, 646, 1 the 2nd Sino-French Workshop

  43. Conclusion • Various astronomical observations suggests a universe that is lightweight (m~1/3), flat and accelerating. • Current astronomical data prefer w to cross over -1. • Quintom and interacting Chaplygin gas are dark energy models in which w can cross over -1. • MFE is an alternative to DE as acceleration mechanism. Combinations of current astronomical data can provide stringent constraints on its model parameters. • MFEcosmology can not be the mechanism for acceler-ation starting from z > 1.0. • DGP model is disfavored by current SNeIa and fgas of galaxy clusters. the 2nd Sino-French Workshop

  44. Thanks for all your patience! & Welcome to visit BNU!

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