Quasi-particle Model in hot QCD

Magnetic quasi-particles in hot QCD predict Casimir scaling for the tension $\sigma$ of spatial Wilson loops. Recently this scaling has been verified on the lattice to 1--2% precision. We review how spatial loops tell us about the nature of the plasma state. The strong first order nature for more than five colours and the fast drop of the topological susceptibilty at $T_c$ found in simulations of hot quenched QCD are consistent with a quasi-particle picture valid down to the critical temperature. The magnetic quasi-particles will Bose condense in the ground state below $T_c$, and may behave like a dilute Bose gas down to T=0. The model fixes the diluteness as $\sigma/m_M^2$. This is a small number for all temperatures.