A kinematical approach to dark energy studies

Abstract

We present and employ a new kinematical approach to cosmological `dark energy' studies. We construct models in terms of the dimensionless second and third derivatives of the scale factor a(t) with respect to cosmic time t, namely the present-day value of the deceleration parameter q_0 and the cosmic jerk parameter, j(t). An elegant feature of this parameterization is that all LCDM models have j(t)=1 (constant), which facilitates simple tests for departures from the LCDM paradigm. Applying our model to the three best available sets of redshift-independent distance measurements, from type Ia supernovae and X-ray cluster gas mass fraction measurements, we obtain clear statistical evidence for a late time transition from a decelerating to an accelerating phase. For a flat model with constant jerk, j(t)=j, we measure q_0=-0.81+-0.14 and j=2.16+0.81-0.75, results that are consistent with LCDM at about the 1sigma confidence level. A standard `dynamical' analysis of the same data, employing the Friedmann equations and modeling the dark energy as a fluid with an equation of state parameter, w (constant), gives Omega_m=0.306+0.042-0.040 and w=-1.15+0.14-0.18, also consistent with LCDM at about the 1sigma level. In comparison to dynamical analyses, the kinematical approach uses a different model set and employs a minimum of prior information, being independent of any particular gravity theory. The results obtained with this new approach therefore provide important additional information and we argue that both kinematical and dynamical techniques should be employed in future dark energy studies, where possible. Our results provide further interesting support for the concordance LCDM paradigm.

12 pages, 5 figures, 2 tables. Accepted for publication in MNRAS

References in corpus (6)

• Dynamics of dark energy
• Can dark energy evolve to the Phantom?
• WMAP constraints on low redshift evolution of dark energy
• Detection of the ISW and SZ effects from the CMB-Galaxy correlation
• Observational constraints on self-accelerating cosmology
• Cross-correlation of WMAP 3rd year and the SDSS DR4 galaxy survey: new evidence for Dark Energy

Cited by in corpus (22)

• Dark Energy and the Accelerating Universe
• Observational Constraints on the Nature of the Dark Energy: First Cosmological Results from the ESSENCE Supernova Survey
• Dark Energy and Gravity
• Energy conditions in f(R)-gravity
• Kinematic Constraints to the Transition Redshift from SNe Ia Union Data
• Mapping the Cosmological Expansion
• Quantum Stability of a w < - 1 Phase of Cosmic Acceleration
• Constraining f(R) theories with the energy conditions
• Cosmographic Hubble fits to the supernova data
• A sub-horizon framework for probing the relationship between the cosmological matter distribution and metric perturbations
• The cosmic snap parameter in f(R) gravity
• When did cosmic acceleration start? How fast was the transition?
• Bayesian Analysis and Constraints on Kinematic Models from Union SNIa
• Model independent constraints on the cosmological expansion rate
• Constraints on Kinematic Model from Recent Cosmic Observations: SN Ia, BAO and Observational Hubble Data
• Scaling relations of the colour-detected cluster RzCS 052 at z=1.016 and of some other high redshift clusters
• How strong is the evidence for accelerated expansion?
• Cosmography: Extracting the Hubble series from the supernova data
• Testing the DGP model with gravitational lensing statistics
• The prospects for constraining dark energy with future X-ray cluster gas mass fraction measurements
• Realistic Equations of State for the Primeval Universe
• Interacting Constituents in Cosmology