Flatness without CMB: The Entanglement of Spatial Curvature and Dark Energy Equation of State

• Published in: The Astrophysical journal Vol. 877; no. 2; pp. 107 - 112
• Main Authors: Xu, Haoting, Huang, Zhiqi, Liu, Zhenjie, Miao, Haitao
• Format: Journal Article
• Language: English
• Published: Philadelphia The American Astronomical Society 01.06.2019; IOP Publishing
• Subjects: Astrophysics; Big Bang theory; Constraints; cosmic background radiation; Cosmic microwave background; cosmological parameters; cosmology: observations; Curvature; Dark energy; Dependence; Energy equation; Entanglement; Equations of state; Flatness; inflation; Infrared telescopes; Large scale structure of the universe; large-scale structure of universe; Parameterization; Polls & surveys; Red shift
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab1b25

The cosmic spatial curvature parameter k is constrained, primarily by cosmic microwave background data, to be very small. Observations of the cosmic distance ladder and the large-scale structure can provide independent checks of the cosmic flatness. Such late-universe constraints on k, however, are sensitive to the assumptions of the nature of dark energy. For minimally coupled scalar-field models of dark energy, the equation of state w has nontrivial dependence on the cosmic spatial curvature k. Such dependence has not been taken into account in previous studies of future observational projects. In this paper we use the w parameterization proposed by Miao & Huang, where the dependence of w on k is encoded, and perform a Fisher forecast on mock data of three benchmark projects: a Wide Field InfraRed Survey Telescope-like SNe Ia survey, a Euclid-like spectroscopic redshift survey, and a Large Synoptic Survey Telescope-like photometric redshift survey. We find that the correlation between k and w is primarily determined by the data rather than by the theoretical prior. We thus validate the standard approaches of treating k and w as independent quantities.