Confronting Braneworld Cosmology with Supernova data and Baryon   Oscillations
  Braneworld cosmology has several attractive and distinctive features. For instance the effective equation of state in braneworld models can be both quintessence-like (w_0 \geq -1) as well as phantom-like (w_0 \leq -1). Models with w_0 \geq -1 (w_0 \leq -1) are referred to as Brane 2 (Brane 1) and correspond to complementary embeddings of the brane in the bulk. (The equation of state in Brane 1 can successfully cross the `phantom divide' at w = -1.) In this paper we compare the predictions of braneworld models to two recently released supernova data sets: the `Gold' data (Riess et al, 2004) and the data from the Supernova Legacy Survey (SNLS) (Astier et al, 2005). We also incorporate the recent discovery of the baryon acoustic peak in the Sloan Digital Sky Survey (Eisenstein et al, 2005) into our analysis. Our main results are that braneworld models satisfy both sets of SNe data. Brane 1 (with w_0 \leq -1) shows very good agreement with data for values of the matter density bounded {\em from below}: \Omega_m \geq 0.25 (Gold) and $\Omega_m \geq 0.2 (SNLS). On the other hand Brane 2 (with w_0 \geq -1) shows excellent agreement with data for values of the matter density which are bounded {\em from above}: \Omega_m \leq 0.45 (Gold) and \Omega_m \leq 0.35 (SNLS). The DGP model is excluded at 3\sigma by SNLS and at 1\sigma by the Gold dataset. Braneworld models with future `quiescent' singularities (at which the Hubble parameter and the matter density remain finite but higher derivatives of the expansion factor diverge) are excluded by both datasets. 
Ujjaini Alam and Varun Sahni