—Title: Reconstructing Horndeski models from the effective field theory of dark energy

—Abstract: Studying the effects of dark energy and modified gravity on cosmological scales has led to a great number of physical models being developed. The effective field theory (EFT) of dark energy allows an efficient exploration of this large model space. However, constraints on such parametrized EFT coefficients cannot be trivially connected to fundamental covariant theories. In this talk I will present a reconstruction of the class of covariant Horndeski scalar-tensor theories that reproduce the same background dynamics and linear perturbations as a given EFT action. I will then discuss some applications as well as the implications for many of these models from the recent GW170817 neutron star merger.