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Browsing Articles by Subject "ECL19"

Now showing 1 - 6 of 6
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    Debiasing Cosmic Gravitational Wave Sirens [Article]
    (NURIS; Energetic Cosmos Laboratory, 2019-05-27) Keeley, Ryan E.; Shafieloo, Arman; L'Huillier, Benjamin; Linder, Eric V.
    Accurate estimation of the Hubble constant, and other cosmological parameters, from distances measured by cosmic gravitational wave sirens requires sufficient allowance for the dark energy evolution. We demonstrate how model independent statistical methods, specifically Gaussian process regression, can remove bias in the reconstruction of H(z), and can be combined model independently with supernova distances.
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    Developments in Cosmic Growth and Gravitation [Article]
    (NURIS; Energetic Cosmos Laboratory, 2019-04-23) Linder, Eric V.
    Cosmic surveys of large scale structure have imaged hundreds of millions of galaxies and mapped the 3D positions of over a million. Surveys starting over the next few years will increase these numbers more than tenfold. Simultaneously, developments in extracting information on dark energy, dark matter, neutrinos, and gravity on cosmic scales have advanced greatly, with many important works from Asian institutions.
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    Modified Gravity Away from a Lambda CDM Background [Article]
    (NURIS; Energetic Cosmos Laboratory, 2019-05-01) Brando, Guilherme; Falciano, Felipe T.; Linder, Eric V.; Velten, Hermano E. S.
    Within the effective field theory approach to cosmic acceleration, the background expansion can be specified separately from the gravitational modifications. We explore the impact of modified gravity in a background different from a cosmological constant plus cold dark matter (ΛCDM) on the stability and cosmological observables, including covariance between gravity and expansion parameters. In No Slip Gravity the more general background allows more gravitational freedom, including both positive and negative Planck mass running. We examine the effects on cosmic structure growth, as well as showing that a viable positive integrated Sachs-Wolfe effect crosscorrelation easily arises from this modified gravity theory.
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    No Run Gravity[Article]
    (NURIS; Energetic Cosmos Laboratory, 2019-03-05) Linder, Eric V.
    Considering the dark energy/gravity landscape if next generation surveys of galaxies, cosmic microwave background radiation, and gravitational waves do not find clear modification of gravity, we develop No Run Gravity as a counterexample to the conclusion that this would imply general relativity with an expansion history described by an equation of state w(z). No Run Gravity is a cubic Horndeski theory with a constant Planck mass, no gravitational slip, and no modification of gravitational waves, but a rich phenomenology beyond w(z). We calculate the evolution of gravitational strength, sound speed, and cosmic growth within the theory and project sensitivities for upcoming DESI redshift space distortion data.
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    On the Use of Fast Radio Burst Dispersion Measures as Distance Measures[Article]
    (NURIS; Energetic Cosmos Laboratory, 2019-03-19) Kumar, Pawan; Linder, Eric V.
    Fast radio bursts appear to be cosmological signals whose frequency-time structure provides a dispersion measure. The dispersion measure is a convolution of the cosmic distance element and the electron density, and contains the possibility of using these events as new cosmological distance measures. We explore the challenges of extracting the distance in a robust manner, and estimate the systematics control needed for fast radio bursts to become a competitive distance probe. The methodology can also be applied to their use for mapping electron density fluctuations or helium reionization.
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    Photometric Supernovae Redshift Systematics Requirements [Article]
    (NURIS; Energetic Cosmos Laboratory, 2019-07-03) Linder, Eric V.; Mitra, Ayan
    Imaging surveys will find many tens to hundreds of thousands of Type Ia supernovae in the next decade, and measure their light curves. In addition to a need for characterizing their types and subtypes, a redshift is required to place them on a Hubble diagram to map the cosmological expansion. We investigate the requirements on redshift systematics control in order not to bias cosmological results, in particular dark energy parameter estimation. We find that additive and multiplicative systematics must be constrained at the few ×10^(−3) level, effectively requiring spectroscopic followup for robust use of photometric supernovae. Catastrophic outliers need control at the subpercent level. We also investigate sculpting the spectroscopic sample.