After discussing theoretical motivations for a strongly-interacting top quark, I will present its phenomenology at current and future colliders, showing that the characteristic four-top contact operators give rise to the most important effects. Hadron colliders can probe these operators directly, whereas lepton colliders have indirect sensitivity through renormalization group evolution. I will discuss the impact on composite Higgs models with a strongly-coupled top, and show that four-top probes provide the best sensitivity on the compositeness scale at the energy frontier. In addition, I will comment on the mild but persisting excesses observed by ATLAS and CMS in multilepton + jets final states, entertaining the possibility that they may arise from such new physics scenario.
With support from FCT through project UIDB/00777/2020
