L. Perivolaropoulos Department of Physics University of Ioannina Open page

New High Quality Cosmological Data have confirmed and mapped in detail the accelerating expansion SNLS astro-ph/ Gold06-HST astro-ph/ Essence astro-ph/ The Cosmological Constant (w=-1) remains consistent with all current data as a driving force of the acceleration. An Evolving Dark Energy Density (w=w(t)) is also allowed by the data and a subset of the allowed evolving forms is inconsistent with General Relativity. Scalar Tensor extensions of General Relativity are consistent with the full range of allowed expansion histories. Demanding consistency of Scalar-Tensor theories with solar system tests and full range of allowed expansion histories implies constraints on Newton’s constant evolution G(t)

Directly Observable Dark Energy (Inferred) No Yes Flat Friedmann Equation Not Consistent

(from large scale structure observations) Friedman eqn I: Friedman eqn II:

SNLS Truncated Gold Full Gold S. Nesseris, L.P. astro-ph/ Phys.Rev.D72:123519,2005 Gold Dataset (157 SNeIa): Riess et. al SNLS (115 SNeIa): Astier et. al Q.: Can we get better fits to the data?

All best fit parameterizations cross the phantom divide at z~0.25 Lazkoz, Nesseris, LP 2005

+: Quintessence -: Phantom To cross the w=-1 line the kinetic energy term must change sign (impossible for single phantom or quintessence field) Generalization for k-essence:

Trunc. Gold (140 points, z<1) Full Gold (157 points, z<1.7)SNLS (115 points z<1) SNLS data show no trend for crossing the phantom divide w=-1! S. Nesseris, L.P. Phys. Rev. D72:123519, 2005 astro-ph/

Gold dataset Riess -et. al. (2004) SNLS dataset Astier -et. al. (2005) Other data: CMB, BAO, LSS, Clusters S. Nesseris, L.P., astro-ph/ , JCAP 0701:018,2007 Other data: CMB, BAO, LSS, Clusters Gold dataset Riess -et. al. (2004) SNLS dataset Astier -et. al. (2005) Other data: CMB, BAO, LSS, Clusters Minimize: Eisenstein et. al Wang, Mukherjee 2006 Allen et. al dF:Verde et. al. MNRAS 2002

Riess et. al. astro-ph/ Subsets of Gold : Q : What is the origin of the mild (2σ) tension between Gold and SNLS?

S. Nesseris, LP astro-ph/ JCAP 0702:025,2007 Compare Random Data Subtraction with Subset Data Subtraction

Wood-Vasey et. al astro-ph/

Q1: What theories are consistent with range of observed H(z)? Cosmological Constant Quintessence Extended (Scalar–Tensor) Quintessence f(R) Modified Gravity 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

Consistency Requirements: S. Nesseris, LP, astro-ph/ Phys.Rev.D75:023517,2007 Q.: What constraints do the consistency requirements imply for H(z), F(z) at low z and are these constraints respected by observations?

Express F i in terms of G(t) current time derivatives: Ignored : (Solar System Tests, Pitjeva 2005)

Freezing Thawing

Freezing Thawing

Upcoming Solar System Constraints on g 2 : J. Mueller 2006 E. Pitjeva 2007 Lower bound on g 2 :

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 χ 2

The shift of the contours is not significant compared to the area of the contours. S. Nesseris, LP, astro-ph/ Phys.Rev.D75:023517,2007

Observational Probes of the Accelerating Expansion w(z) is close to -1 w(z) crossing the w=-1 w(z) crossing the w=-1 Inconsistent with Minimally Coupled Quintessence and also with Scalar Tensor Quintessence if G(t) is increasing with time. Consistency of Scalar-Tensor Quintessence with local gravity and crossing of w=-1

Growth Factor: Growth Factor Evolution (Linear-Fourier Space): General Relativity: DGP: Scalar Tensor: Modified Poisson: Koyama and Maartens (2006) Sealfon et. al. (2004) Esposito-Farese and Polarski (2001) Uzan (2006)

ΛCDM (SnIa best fit, Ω m =0.26 ) DGP SnIa best fit + Flat Constraint Scalar Tensor (α=-0.5, Ω m =0.26 ) Flat Matter Only S. Nesseris, L.P. astro-ph/ JCAP 0701:018,2007 Verde et. al. MNRAS 2002 Hawkins et. al. MNRAS 2003

Observational Probes of the Accelerating Expansion w(z) is close to -1 w(z) crossing the w=-1 w(z) crossing the w=-1 Inconsistent with Minimally Coupled Quintessence and also with Scalar Tensor Quintessence if G(t) is increasing with time. Consistency of Scalar-Tensor Quintessence with crossing of w=-1

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

Wood-Vasey et. al astro-ph/

Plausibility Arguments + Numerical Simulations Caldwel, Linder 2005 V(Φ) Φ Φ Thawing Thaw Accelerate Freezing Decelerate Freeze

SnIa Obs Know L Measure l(z)

SnIa Obs

2 12 Know L Measure l(z) Distance Modulus: 1 Flat

Growth Factor: Growth Factor Evolution (Linear-Fourier Space): General Relativity: DGP: Scalar Tensor: Modified Poisson: Koyama and Maartens (2006) Sealfon et. al. (2004) Esposito-Farese and Polarski (2001) Uzan (2006)

ΛCDM (SnIa best fit, Ω m =0.26 ) DGP SnIa best fit + Flat Constraint Scalar Tensor (α=-0.5, Ω m =0.26 ) Flat Matter Only S. Nesseris, L.P. astro-ph/ Verde et. al. MNRAS 2002 Hawkins et. al. MNRAS 2003

V(Φ) Φ Φ Thawing Thaw Accelerate Freezing Decelerate Freeze Q.: Can the observed equation of state w(z) distinguish between the two classes of models?

Plausibility Arguments + Numerical Simulations Caldwel, Linder 2005 V(Φ) Φ Φ Thawing Thaw Accelerate Freezing Decelerate Freeze

Lower bound on g 2 : Chevallier-Polarski-Linder