[Paper Review] Confronting Dark Energy Models with Astrophysical Data

John Ellis, Nick E. Mavromatos+2 more|arXiv (Cornell University)|Apr 12, 2006

Cosmology and Gravitation Theories3 citations

TL;DR

This paper evaluates dark energy models—LambdaCDM, super-horizon dark matter (SHDM), and Q-cosmology—against high-redshift supernova and baryon acoustic oscillation (BAO) data. It finds that LambdaCDM provides an excellent fit to combined supernova data, is consistent with BAO and WMAP constraints on matter density, and that SHDM also fits well, while a refined Q-cosmology model with off-shell corrections fits supernova data very well, though a naive version fails.

ABSTRACT

We discuss fits of cosmological dark energy models to the available data on high-redshift supernovae and baryon oscillations. We consider a conventional model with Cold Dark Matter and a cosmological constant (LambdaCDM), a model invoking super-horizon perturbations (SHDM) and models based on Liouville strings in which dark energy is provided by a rolling dilaton field (Q-cosmology). The two main high-redshift supernova data sets give compatible constraints on these models. We find that LambdaCDM fits very well the combined supernova data sets. These are also compatible with the data on baryon acoustic oscillations, yielding together a determination of the matter density in the LambdaCDM (assuming a flat Universe) which is comparable with that provided by the three-year WMAP data. The supernova data are also fit quite well by the super-horizon model. A naive version of the Q-cosmology model does not fit the supernova data, but a simple parametrization of the full version of the model that includes off-shell effects fits the data very well. A detailed discussion of the model-dependent off-shell corrections to the Q-cosmology model is given in the Appendix.

Motivation & Objective

• To test the compatibility of various dark energy models with high-redshift supernova and baryon acoustic oscillation (BAO) data.
• To assess whether the standard LambdaCDM model, super-horizon dark matter (SHDM), and Q-cosmology (based on rolling dilaton fields) can explain current astrophysical observations.
• To determine the viability of Q-cosmology after including off-shell corrections, which are known to affect its phenomenology.
• To compare the constraints on matter density from supernova and BAO data with those from the three-year WMAP results in the context of a flat LambdaCDM model.

Proposed method

• Fits the LambdaCDM model, SHDM, and Q-cosmology models to two main high-redshift supernova data sets.
• Applies constraints from baryon acoustic oscillation (BAO) data to cross-validate model fits.
• Uses a parametrization of the full Q-cosmology model that includes off-shell effects, which are otherwise difficult to compute directly.
• Compares model predictions with observational data using statistical goodness-of-fit criteria.
• Employs a flat Universe assumption to derive matter density constraints in the LambdaCDM model.
• Analyzes model-dependent off-shell corrections in detail, as presented in the Appendix, to refine Q-cosmology predictions.

Experimental results

Research questions

• RQ1 How well does the standard LambdaCDM model fit the combined high-redshift supernova and BAO data?
• RQ2 To what extent does the super-horizon dark matter (SHDM) model reproduce the observed supernova luminosity distances?
• RQ3 Can a naive version of the Q-cosmology model, based on a rolling dilaton field, explain the supernova data?
• RQ4 How do off-shell corrections in the full Q-cosmology model affect its compatibility with supernova observations?
• RQ5 What is the consistency of matter density constraints derived from supernova and BAO data with those from the three-year WMAP results in the LambdaCDM framework?

Key findings

• The LambdaCDM model provides an excellent fit to the combined high-redshift supernova data sets.
• The supernova data are consistent with the baryon acoustic oscillation (BAO) data, yielding a matter density constraint in the LambdaCDM model that matches the three-year WMAP result.
• The super-horizon dark matter (SHDM) model also fits the supernova data quite well.
• A naive version of the Q-cosmology model, without off-shell corrections, fails to fit the supernova data.
• A refined parametrization of the full Q-cosmology model that includes off-shell effects fits the supernova data very well.
• The detailed analysis of off-shell corrections in the Q-cosmology model is provided in the Appendix, showing their critical role in model viability.