Model selection with baryonic acoustic oscillations in the Lyman-α forest

The recent release of the final, complete survey of Lyman-α baryonic acoustic oscillation measurements provides the most significant and accurate data base for studying cosmic geometry at an effective redshift , which is inaccessible to other sources. In this paper, we use these data to select among four distinct cosmologies: Planck ΛCDM, the universe, the Milne universe and the Einstein-de Sitter universe. Given the breadth and depth of the Lyman-α study, this BAO measurement alone provides a strong model comparison, complementary to previous studies that combined Lyman-α data with measurements at lower redshifts. Though both approaches are useful, the latter tends to dilute the disparity between model predictions and the observations. We therefore examine how the models compare to each other strictly based on the BAO scale measured in the Lyman-α forest and background quasars. We find that the Milne universe and the Einstein-de Sitter universe are strongly ruled out by these data. There is also strong evidence disfavoring the standard model. The Lyman-α measurements are completely consistent with the cosmic geometry predicted by . As such, evidence continues to grow that the zero active mass condition from general relativity ought to be an essential ingredient in ΛCDM.