Next step in gravity and cosmology: fundamental theory or data-driven models?

Abstract

We comment on the difference between bottom-up (i.e., data-driven, ad hoc) and top-down (i.e., derived from a fundamental theory of gravitational interactions) cosmological models, their respective status, predictive power and viability. We fuel the debate on whether present and future research on theoretical models of inflation, dark energy and gravitational waves should concentrate on bottom-up models such as $f(R)$, Horndeski or DHOST theories or on cosmological models of quantum gravity.