Average observational quantities in the timescape cosmology

摘要

We examine the properties of a recently proposed observationally viable alternative to homogeneouscosmology with smooth dark energy, the timescape cosmology. In the timescape modelcosmic acceleration is realized as an apparent effect related to the calibration of clocks and rods ofobservers in bound systems relative to volume–average observers in an inhomogeneous geometry inordinary general relativity. The model is based on an exact solution to a Buchert average of theEinstein equations with backreaction. The present paper examines a number of observational testswhich will enable the timescape model to be distinguished from homogeneous cosmologies with acosmological constant or other smooth dark energy, in current and future generations of dark energyexperiments. Predictions are presented for: comoving distance measures; H(z); the equivalent ofthe dark energy equation of state, w(z); the Om(z) measure of Sahni, Shafieloo and Starobinsky;the Alcock–Paczy´nski test; the baryon acoustic oscillation measure, DV ; the inhomogeneity test ofClarkson, Bassett and Lu; and the time drift of cosmological redshifts. Where possible, the predictionsare compared to recent independent studies of similar measures in homogeneous cosmologieswith dark energy. Three separate tests with indications of results in possible tension with the CDMmodel are found to be consistent with the expectations of the timescape cosmology.