Constraints on the Cardassian Expansion from the Cosmic Lens All‐Sky Survey Gravitational Lens Statistics

The existence of a dark energy component has usually been invoked as the mostplausible way to explain the recent observational results. However, it is alsowell known that effects arising from new physics (e.g., extra dimensions) canmimic the gravitational effects of a dark energy through a modification of theFriedmann equation. In this paper we investigate some observationalconsequences of a flat, matter dominated and accelerating/decelerating scenarioin which this modification is given by $H^{2} = g(\rho_m, n, q)$ where$g(\rho_m, n, q)$ is a new function of the energy density $\rho_m$, theso-called generalized Cardassian models. We mainly focus our attention on theconstraints from the recent Cosmic All Sky Survey (CLASS) lensing sample on theparameters $n$ and $q$ that fully characterize the models. We show that, for alarge interval of the $q - n$ parametric space, these models are in agreementwith the current gravitational lenses data. The influence of these parameterson the acceleration redshift, i.e., the redshift at which the universe beginsto accelerate, and on the age of the universe at high-redshift is alsodiscussed.Comment: 6 pages, 4 figures, AAS late