  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.
