Model-independent Constraints on Cosmic Curvature and Opacity

Abstract

In this paper, we propose to estimate the spatial curvature of the universe and the cosmic opacity in a model-independent way with expansion rate measurements, $H(z)$, and type Ia supernova (SNe Ia). On the one hand, using a nonparametric smoothing method Gaussian process, we reconstruct a function $H(z)$ from opacity-free expansion rate measurements. Then, we integrate the $H(z)$ to obtain distance modulus ${\mu }_{\mathrm{H}}$, which is dependent on the cosmic curvature. On the other hand, distances of SNe Ia can be determined by their photometric observations and thus are opacity-dependent. In our analysis, by confronting distance moduli ${\mu }_{\mathrm{H}}$ with those obtained from SNe Ia, we achieve estimations for both the spatial curvature and the cosmic opacity without any assumptions for the cosmological model. Here, it should be noted that light curve fitting parameters, accounting for the distance estimation of SNe Ia, are determined in a global fit together with the cosmic opacity and spatial curvature to get rid of the dependence of these parameters on cosmology. In addition, we also investigate whether the inclusion of different priors for the present expansion rate ($H_0$: global estimation, $67.74\pm 0.46\mathrm{km}{\mathrm{s}}^{-1}\mathrm{Mp}{\mathrm{c}}^{-1}$, and local measurement, $73.24\pm 1.74\mathrm{km}{\mathrm{s}}^{-1}\mathrm{Mp}{\mathrm{c}}^{-1}$) exert influence on the reconstructed $H(z)$ and the following estimations of the spatial curvature and cosmic opacity. Results show that, in general, a spatially flat and transparent universe is preferred by the observations. Moreover, it is suggested that priors for $H_0$ matter a lot. Finally, we find that there is a strong degeneracy between the curvature and the opacity.

7 pages, 3 figures and 2 tables

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Cited by in corpus (8)

• Model-independent constraints on cosmic curvature: implication from updated Hubble diagram of high-redshift standard candles
• Model-independent Distance Calibration and Curvature Measurement using Quasars and Cosmic Chronometers
• Constraining the curvature density parameter in cosmology
• Exploring the Hubble Tension and Spatial Curvature from the Ages of Old Astrophysical Objects
• Model-independent test for the cosmic distance duality relation with Pantheon and eBOSS DR16 quasar sample
• Model-independent constraints on cosmic curvature: implication from the future gravitational wave observation DECIGO
• Unbiased Cosmic Opacity Constraints from Standard Sirens and Candles
• Flatness without CMB - the Entanglement of Spatial Curvature and Dark Energy Equation of State