Weikang Lin

Cosmological discordances: A new measure, marginalization effects, and application to geometry versus growth current data sets

The continuous progress toward more precise cosmological surveys and experiments has galvanized recent interest into consistency tests on cosmological parameters and models. At the heart of this effort is quantifying the degree of inconsistency between two or more cosmological data sets. We introduce an intuitive moment-based measure we call the \textit{index of inconsistency} (IOI) and show that it is sensitive to the separation of the means, the size of the constraint ellipsoids, and their orientations in the parameter space. We find that it tracks accurately the inconsistencies when present. Next, we show that parameter marginalization can cause a loss of information on the inconsistency between two experiments and we quantify such a loss using the drop in IOI. In order to zoom on a given parameter, we define the relative residual IOI and the relative drop in IOI. While these two quantities can provide insights on the parameters that are most responsible for inconsistencies, we find that the full IOI applied to the whole parameter spaces is what must be used to correctly reflect the degree of inconsistency between two experiments. We discuss various properties of IOI, provide its eigenmode decomposition, and compare it to other measures of discordance. Finally, we apply IOI to current geometry data sets (i.e. an improved Supernovae Type Ia compilation, baryon acoustic oscillations from 6dF, SDSS MGS and Lyman-

Testing gravity theories using tensor perturbations

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Effects of self-calibration of intrinsic alignment on cosmological parameter constraints from future cosmic shear surveys

forest, and high-

Ultra faint dwarf galaxies: an arena for testing dark matter versus modified gravity

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Averaged universe confronted with cosmological observations: A fully covariant approach

CMB temperature data from Planck-2015) versus growth data sets (i.e. Redshift Space Distortions from WiggleZ and SDSS, Weak Lensing from CFHTLenS, CMB Lensing, Sunyav-Zeldovich effect, and low-

Cosmological discordances. II. Hubble constant, Planck and large-scale-structure data sets

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Probing gravity theory and cosmic acceleration using (in)consistency tests between cosmological data sets.

CMB temperature and polarization data from Planck-2015). We find that a persistent inconsistency is present between the two data sets. This could reflect the presence of systematics in the data or inconsistencies in the underlying model.

Seeking insights on gravity theory and cosmic acceleration from consistency tests between cosmological data sets.

Primordial gravitational waves constitute a promising probe of the very early Universe and the laws of gravity. We study in this work changes to tensor-mode perturbations (TMPs) that can arise in various proposed modified gravity (MG) theories. These include additional friction effects, nonstandard dispersion relations involving a massive graviton, a modified speed, and a small-scale modification. We introduce a physically motivated parameterization of these effects and use current available data to obtain exclusion regions in the parameter spaces. Taking into account the foreground subtraction, we then perform a forecast analysis focusing on tensor-mode MG parameters as constrained by future experiments COrE, Stage-IV and PIXIE. For a fiducial value of the tensor-to-scalar ratio

Testing gravity theories using primordial gravitational waves and CMB experiments

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Effects of Self-Calibration of Intrinsic Alignment on Cosmological Parameter Constraints from Future Cosmic Shear Surveys

, we find that an additional friction of