Gribov horizon and BRST symmetry: a pathway to confinement

We summarize the construction of the Gribov-Zwanziger action and how it leads to a scenario which explains the confinement of gluons, in the sense that the elementary gluon excitations violate positivity. Then we address the question of how one can construct operators within this picture whose one-loop correlation functions have the correct analytic properties in order to correspond to physical excitations. For this we introduce the concept of i-particles.