CM4 - Tensions on LCDM cosmological model and model-independent constraints |
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Speaker |
Nesseris, Savvas |
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Tension and constraints on modified gravity from growth rate and Planck data |
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Abstract |
We construct an updated and extended compilation of growth rate data consisting of 34 points and including corrections for model dependence. In order to maximize the independence of the datapoints we also construct a subsample of this compilation which consists of 18 datapoints. We test the consistency of this dataset with the best fit Planck15/LCDM parameters in the context of General Relativity (GR) using the evolution equation for the growth factor \delta(a) with a wCDM background. We find tension at the ∼3\sigma level between the best fit parameters w (the dark energy equation of state), \Omega_m (the matter density parameter) and \sigma_8 (the matter power spectrum normalization on scales 8h−1Mpc) and the corresponding Planck15/ΛCDM parameters. We show that the tension disappears if we allow for evolution of the effective Newton's constant, parametrized as Geff(a)/GN=1+ga(1−a)^n−ga(1−a)^{2n} with n≥2 where ga, n are parameters of the model, a is the scale factor and z=1/a−1 is the redshift. |
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