WMAP constraints on Cardassian model

Abstract

We have investigated the constraints on the Cardassian model using the recent results from the Wilkinson Microwave Anisotropy Probe (WMAP) for the locations of the peaks of the Cosmic Microwave Background (CMB) anistropy spectrum. We find that the model is consistent with the recent observational data for certain range of the model parameter $n$ and the cosmological parameters. We find that the Cardassian model is favoured compared to $Λ$CDM model, for a higher spectral index ($n_s \approx 1$) together with lower value of Hubble parameter $h$ ($h\leq 0.71$). But for smaller values of $n_s$, both $Λ$CDM and Cardassian are equally favoured. Also, irrespective of Supernova constraint, CMB data alone predicts current acceleration of the universe in this model. We have also studied the constraint on the $σ_{8}$, the rms density fluctuations at $8h^{-1}$ Mpc scale.