  We consider an effective field theory description of beyond-quasi-particle
excitations aiming to associate the transport properties of the system with the
spectral density of states. Tuning various properties of the many-particle
correlations, we investigate how the robust microscopic features are translated
into the macroscopic observables like shear viscosity and entropy density. The
liquid-gas crossover is analysed using several examples. A thermal constraint
on the fluidity measure, the ratio of shear viscosity to entropy density, is
discussed.
