ECL_Articles

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Browsing ECL_Articles by Subject "cosmology"

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    DETERMINING MODEL-INDEPENDENT H0 AND CONSISTENCY TESTS
    (arxiv, 2020) Liao, Kai; Shafieloo, Arman; Keeley, Ryan E.; Linder, Eric V.
    We determine the Hubble constant H0 precisely (2.3% uncertainty) in a manner independent of cosmological model through Gaussian process regression, using strong lensing and supernova data. Strong gravitational lensing of a variable source can provide a time-delay distance D∆t and angular diameter distance to the lens Dd. These absolute distances can anchor Type Ia supernovae, which give an excellent constraint on the shape of the distance-redshift relation. Updating our previous results to use the H0LiCOW program’s milestone dataset consisting of six lenses, four of which have both D∆t and Dd measurements, we obtain H0 = 72.8 +1.6 −1.7 km/s/Mpc for a flat universe and H0 = 77.3 +2.2 −3.0 km/s/Mpc for a non-flat universe. We carry out several consistency checks on the data and find no statistically significant tensions, though a noticeable redshift dependence persists in a particular systematic manner that we investigate. Speculating on the possibility that this trend of derived Hubble constant with lens distance is physical, we show how this can arise through modified gravity light propagation, which would also impact the weak lensing σ8 tension
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    ItemOpen Access
    EXPLORING EARLY AND LATE COSMOLOGY WITH NEXT GENERATION SURVEYS
    (PHYSICAL REVIEW D, 2020) Brando, Guilherme; Linder, Eric V.
    Perturbations from inflation evolve into large scale structure of the late universe, and encode abundant cosmic structure formation physics. We allow freedom in the primordial power spectrum, rather than assuming a power law scale dependence, to study its impact on cosmological parameter determination. Combining various generations of cosmic microwave background (CMB) data and galaxy redshift survey data, we investigate the constraints on reconstruction of the primordial curvature perturbation power spectrum and the late time cosmology, especially the sum of neutrino masses. We quantify how each successive generation, in CMB and galaxy surveys, provides significant improvements, often by factors of several. By using CMB polarization information over a broad range of angular scales, and galaxy redshift data in many bins of redshift, one can allow inflationary freedom and still constrain parameters comparably to assuming power law dependence. The primordial power spectrum can be reconstructed at the subpercent level in a dozen wave number bins, while simultaneously fitting the sum of neutrino masses to 14 meV