paper

tension as a hint for a transition in gravitational theory

arXiv:1710.09366 · doi:10.1103/PhysRevD.99.103526

Abstract

We propose a cosmological model, üCDM, based on {\it über-gravity}, which is a canonical ensemble average of many theories of gravity. In this model, we have a sharp transition from (a purely) CDM era to a phase in which the Ricci scalar is a constant. This transition occurs when the Ricci scalar reaches a critical scale or alternatively at a transition redshift, . We use the observations of baryonic acoustic oscillations (BAO) and Supernovae Ia (SNe), as well as the cosmic microwave background (CMB) data to constrain üCDM. This yields km/s/Mpc, and , providing a marginally better fit with a Akaike information criterion of 0.8. %After adding in the data from BAO in the Lyman- forest in quasar spectra, we get , where the best fit occurs at km/s/Mpc, and . Therefore, üCDM can ease the -tension, albeit marginally, with one additional free parameter. We also provide a preliminary study of the linear perturbation theory in üCDM which points to interesting potential {\it smoking guns} in the observations of large scales structure at .

10 pages, 10 figures. CMB data has been added. Title has been changed. This version is compatible with the published one in PRD. Comments are welcome

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