Description
The late-time accelerated expansion of the Universe, revealed by observations of Type Ia supernovae and other cosmological probes, may be explained by extensions of general relativity. Various extended theories of gravity have been proposed to explore gravitational physics beyond general relativity. In this talk, I will focus on constraining such theories using observations of the cosmic microwave background (CMB). In particular, I will consider degenerate higher-order scalar-tensor (DHOST) theories, generalised Proca theories, and a model propagating only two tensor degrees of freedom. To investigate these theories, we have developed a Boltzmann solver incorporating the effective field theory (EFT) approach to gravity. Using this solver, we perform Markov chain Monte Carlo (MCMC) analyses with the Planck 2018 likelihood to derive observational constraints on the EFT parameters characterising each model.
