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L. Perivolaropoulos http://leandros.physics.uoi.gr Department of Physics University of Ioannina

Open page. Crossing the Phantom Divide: Observational Status and Theoretical Implications. S. Nesseris, LP, astro-ph/0610092, astro-ph/0611238. L. Perivolaropoulos http://leandros.physics.uoi.gr Department of Physics University of Ioannina. Main Points.

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L. Perivolaropoulos http://leandros.physics.uoi.gr Department of Physics University of Ioannina

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  1. Open page Crossing the Phantom Divide: Observational Status and Theoretical Implications S. Nesseris, LP, astro-ph/0610092, astro-ph/0611238 L. Perivolaropouloshttp://leandros.physics.uoi.gr Department of Physics University of Ioannina

  2. Main Points w(z) is close to -1 w(z) crossing the w=-1 Observational Probes of the Accelerating Expansion Inconsistent with Minimally Coupled Quintessenceand also with Scalar Tensor Quintessenceif G(t) is increasing with time. w(z) crossing the w=-1 Close to Extremum(Solar System) Marginal Consistency of Scalar-Tensor Quintessence withObserved Accelerating Expansion G(t) can not increase rapidly with t(not ‘sharp’ Maximum) SNLS Maximal Agreement of Scalar-Tensor Quintessencewith the Full Parameter RangeofObserved Acelerating Expansion Close to Extremum(Solar System) G(t) decreases with t(close to a Minimum) SNLS

  3. History of Fundamentally New Phenomena Measure Planet Motions Collect Data Tycho-Brache 1588 Parametrize Data: Ellipses Johan Kepler 1621 Parametrize Data ??? Isaac Newton 1687 Physical Law Modified Gravity? or Dark Energy?

  4. Parametrization of H(z)-w(z)

  5. Best Fit Parametrizations (Gold Sample) • All best fit parameterizations cross the phantom divide at z~0.25 • The parametrization with the best χ2is oscillating Crossing Phantom Divide w=-1 Lazkoz, Nesseris, LP 2005

  6. Best Fit (Uncorrelated Gold)

  7. Comparison with SNLS Trunc. Gold (140 points, z<1) SNLS (115 points z<1) Full Gold (157 points, z<1.7) SNLS data show no trend for crossing the phantom divide w=-1! S. Nesseris, L.P. Phys. Rev. D72:123519, 2005 astro-ph/0511040 Q: What do other cosmological data favor?

  8. Best Fits for w(z) Gold dataset Riess -et. al. (2004) SNLS dataset Astier -et. al. (2005) Other data: CMB, BAO, LSS, Clusters Other data: CMB, BAO, LSS, Clusters S. Nesseris, L.P.astro-ph/0610092 Gold dataset Riess -et. al. (2004) SNLS dataset Astier -et. al. (2005) Other data: CMB, BAO, LSS, Clusters Minimize: Wang, Mukherjee 2006 Eisenstein et. al. 2005 2dF:Verde et. al. MNRAS 2002 Allen et. al. 2004

  9. Parameter Contours

  10. New Gold Dataset Riess et. al. astro-ph/0611572

  11. New Gold Dataset Old Gold Filtered Gold+New HST Filtered Gold+New HST+Best of SNLS S. Nesseris, LP in prep.

  12. New Gold Dataset Filtered Gold+New HST+Best of SNLS Old Gold Filtered Gold+New HST

  13. Basic Questions Q1: What theories are consistent with range of observed H(z)? • Cosmological Constant • Quintessence • Extended (Scalar–Tensor) Quintessence • Braneworld models (eg DGP) • Barotropic fluids (eg Chaplygin Gas) Q2: What forms of H(z) are inconsistent with each theory? (forbidden sectors) Q3: What is the overlap of the observationally allowed range of H(z)with the forbidden sector of each theory? Goal:Address Q2-Q3 for Extended Quintessence

  14. Previous Studies: Quintessence ThawingThaw Accelerate V(Φ) Φ V(Φ) FreezingDecelerate Freeze Plausibility Arguments+Numerical Simulations Caldwel, Linder 2005 Φ

  15. Scalar-Tensor Theories: Extended Quintessence Vary ST action in flat FRW background assuming perfect fluid: +

  16. Redshift Space Convert t to z, solve for U and Φ': where Consistency Requirements:

  17. Parameter Constraints: Low Redshift Expansion Express Fi in terms of G(t) current time derivatives: Gannouji, Polarski, Ranquet, Starobinsky astro-ph/0606287 (Solar System Tests, Pitjeva 2005) Ignored :

  18. Low Redshift Expansion Freezing Thawing

  19. The Limits of Extended Quintessence I Freezing Thawing

  20. The Limits of Extended Quintessence II Chevallier-Polarski-Linder Lower bound on g2:

  21. Upcoming Solar System Constraints on g2: J. Mueller 2006 The Limits of Extended Quintessence II Chevallier-Polarski-Linder Lower bound on g2:

  22. Varying G and SnIa Analysis SnIa Absolute Luminosity: Steps of Analysis: 1. Assume G(z) parametrization consistent with Solar System + Nucleosynthesis bounds 2. Consider modified magnitude-redshift relation 3. Minimize χ2

  23. Contour Modification for Varying G The shift of the contours is not significantcompared to the area of the contours.

  24. SUMMARY w(z) is close to -1 w(z) crossing the w=-1 Observational Probes of the Accelerating Expansion Inconsistent with Minimally Coupled Quintessenceand also with Scalar Tensor Quintessenceif G(t) is increasing with time. w(z) crossing the w=-1 Close to Extremum(Solar System) Consistency of Scalar-Tensor QuintessenceObserved Accelerating Expansion G(t) can not increase rapidly with t(not ‘sharp’ Maximum) Maximal Agreement of Scalar-Tensor Quintessencewith the full range of observedAcelerating Expansion Close to Extremum(Solar System) G(t) decreases with t(close to a Minimum)

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