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Is the cosmic acceleration slowing down?

Is the cosmic acceleration slowing down?. Tuo Zhongliang KITPC, CAS April 1st, 2011. Outline. Eternal acceleration or escape eternal acceleration? Cosmographic approach Non-parametrization method Summary. The accelerating expansion. SNIa observations in 1998 find cosmic acceleration.

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Is the cosmic acceleration slowing down?

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  1. Is the cosmic acceleration slowing down? Tuo Zhongliang KITPC, CAS April 1st, 2011

  2. Outline • Eternal acceleration or escape eternal acceleration? • Cosmographic approach • Non-parametrization method • Summary

  3. The accelerating expansion SNIa observations in 1998 find cosmic acceleration. Riess Perlmutter

  4. Concordance model (LCDM) WMAP7 Dark energy: 73.4% Dark matter: 22.2% Normal matter: 4.4%

  5. the big rip R.R.Caldwell, M.Kamionkowski and N.N.Weinberg, Phys.Rev.Lett.91(2003)071301 “Cosmic Doomsday”

  6. Can the universe escape eternal acceleration？ J. D. Barrow, R. Bean and J. Magueijo, Mon.Not.Roy.Astron.Soc.316:L41,2000 A difference of 120 orders of magnitude

  7. Cosmographic approach Redshift expansion y-redshift expansion,

  8. Thus to reduce the systematic error

  9. Hubble parameter For z<zcut or y<ycut, For zcut<z<1.0 or ycut<y<1.0,

  10. Data sets SNeIa: Union2 (R.Amanullah et al. e-Print: arXiv:1004.1711 ) Distance modulus Marginalization over μ0

  11. Data sets Hubble parameter (D. Stern et al. e-Print: arXiv:0907.3149 ) Marginalization over H0

  12. 1-D marginalized probability distribution of q0

  13. Evolution behavior of q(z)

  14. Evolution behaviors of q(z)

  15. Comparison with the Hubble data

  16. Non-parametrization method Independent of the calibration

  17. Reconstructed deceleration parameters

  18. Summary • The universe transited from deceleration from acceleration at higher redshift than what the LCDM model predicts • The universe is still in the stage of accelerating expansion • SNIa data favor a transient acceleration, even with the Hubble parameter data added in.

  19. Thanks!

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