K-mouflage imprints on cosmological observables and data constraints

Abstract

We investigate cosmological constraints on K-mouflage models of modified gravity. We consider two scenarios: one where the background evolution is free to deviate from ΛCDM (K-mouflage) and another one which reproduces a ΛCDM expansion (K-mimic), implementing both of them into the EFTCAMB code. We discuss the main observational signatures of these models and we compare their cosmological predictions to different datasets, including CMB, CMB lensing, SNIa and different galaxy catalogues. We argue about the possibility of relieving the H0 and weak lensing tensions within these models, finding that K-mouflage scenarios effectively ease the tension on the Hubble Constant. Our final 95% C.L. bounds on the ϵ2,0 parameter that measures the overall departure from ΛCDM (corresponding to ϵ2,0 = 0) are −0.04⩽ ϵ2,0 ⩽ 0 for K-mouflage and 0 ⩽ ϵ2,0 ⩽ 0.002 for K-mimic. These translate into an upper bound for the coupling strength: β <0.22 for K-mouflage and β < 0.026 for K-mimic. In the former case the main constraining power comes from changes in the background expansion history, while in the latter case the model is strongly constrained by measurements of the amplitude of matter perturbations. The sensitivity of these cosmological constraints closely matches that of solar system probes. We show that these constraints could be significantly tightened with future ideal probes like CORE.