Browsing by Subject "cosmological constant"

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    Open Access
    FIRST-YEAR SLOAN DIGITAL SKY SURVEY-II (SDSS-II) SUPERNOVA RESULTS: CONSTRAINTS ON NONSTANDARD COSMOLOGICAL MODELS
    (2009) Sollerman, J; Mörtsell, E; Davis, T M; Blomqvist, M; Bassett, B; Becker, A C; Cinabro, D; Filippenko, A V; Foley, R J; Frieman, J; Garnavich, P; Lampeitl, H; Marriner, J; Miquel, R; Nichol, R C; Richmond, M W; Sako, M; Schneider, D P; Smith, M; VanderPlas, J T; Wheeler, J C
    We use the new Type Ia supernovae discovered by the Sloan Digital Sky Survey-II supernova survey, together with additional supernova data sets as well as observations of the cosmic microwave backgr ...
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    Large-scale perturbations on the brane and the isotropy of the cosmological singularity
    (2004) Goheer, Naureen; Dunsby, Peter K S; Coley, Alan; Bruni, Marco
    We present the complete set of propagation and constraint equations for the kinematic and non-local first order quantities which describe general linear inhomogeneous and anisotropic perturbations of a flat FRW braneworld with vanishing cosmological constant and decompose them in the standard way into their scalar, vector and tensor contributions. A detailed analysis of the perturbation dynamics is performed using dimensionless variables that are specially tailored for the different regimes of interest; namely, the low energy GR regime, the high energy regime and the dark energy regime. Tables are presented for the evolution of all the physical quantities, making it easy to do a detailed comparison of the past asymptotic behaviour of the perturbations of these models. We find results that exactly match those obtained in the analysis of the spatially inhomogeneous $G_{2}$ braneworld cosmologies presented recently; i.e., that isotropization towards the ${cal F}_b$ model occurs for $gamma > 4/3$.