arXiv:1802.02255v2 [astro-ph.CO] 15 Feb 2018 Prepared for submission to JCAP Model Selection Using Cosmic Chronometers with Gaussian Processes Fulvio Melia 1,3 and Manoj K. Yennapureddy 2 3 Department of Physics, the Applied Math Program, and Steward Observatory, The University of Arizona, Tucson, AZ 85721 2 Department of Physics, The University of Arizona, Tucson, AZ 85721 E-mail: fmelia@email.arizona.edu; manojy@email.arizona.edu Abstract. The use of Gaussian Processes with a measurement of the cosmic expansion rate based solely on the observation of cosmic chronometers provides a completely cosmology- independent reconstruction of the Hubble constant H (z) suitable for testing different models. The corresponding dispersion σ H is smaller than ∼ 9% over the entire redshift range (0  z  2) of the observations, rivaling many kinds of cosmological measurements available today. We use the reconstructed H (z) function to test six different cosmologies, and show that it favours the R h = ct universe, which has only one free parameter (i.e., H 0 ) over other models, including Planck ΛCDM. The parameters of the standard model may be re-optimized to improve the fits to the reconstructed H (z) function, but the results have smaller p-values than one finds with R h = ct. 1 John Woodruff Simpson Fellow.