Abstract We study long-distance features of the quark-gluon plasma, that are crucial for the dynamics of the system, with an infrared improved framework, the Gribov-Zwanziger quantization. Strikingly, at high temperature we uncover the presence of massless modes that violate the positivity of the quark spectral function. We also report on a study of transport coefficient, where we find a strong enhancement of the bulk viscosity that follows a scaling law similar to strongly coupled theories.