  In this thesis we discuss three separate analysis of various phenomenological
aspects of heavy-ion collisions (HIC). The first one is a possible
generalization of the kinetic theory framework for dense systems. We
investigate its long-time behaviour and the properties of the equilibrium. The
second discussion is about the phenomenological analysis of the azimuthal
asymmetry of the particle yields in a HIC, where we link the initial stage
geometrical asymmetry to the particle yields and examine the possible
organizing mechanisms that could be responsible for such a relation. The third,
and also the most thorough part of the thesis is about the relation of the
spectral density of quasi-particle states and the macroscopic fluidity measure
(the ratio of shear viscosity and the entropy density) and other transport
properties of the system. We extensively study the liquid-gas crossover with
the help of model spectral functions. The main conclusion is that the relative
intensification of the continuum of the scattering states compared to the
quasi-particle peak makes the matter more fluent.
