We propose to model the dissipative hydrodynamics used in description of the multiparticle production processes ($d$-hydrodynamics) by a special kind of the perfect nonextensive fluid ($q$-fluid) where $q$ denotes the nonextensivity parameter appeari
ng in the nonextensive Tsallis statistics. The advantage of $q$-hydrodynamics lies in its formal simplicity in comparison to the $d$-hydrodynamics. We argue that parameter $q$ describes summarily (at least to some extent) all dynamical effects behind the viscous behavior of the hadronic fluid.
Energy spectrum of cosmic rays (CR) exhibits power-like behavior with very characteristic knee structure. We consider a generalized statistical model for the production process of cosmic rays which accounts for such behavior in a natural way either b
y assuming existence of temperature fluctuations in the source of CR, or by assuming specific temperature distribution of CR sources. Both possibilities yield the so called Tsallis statistics and lead to the power-like distribution. We argue that the knee structure arises as result of abrupt change of fluctuations in the source of CR. Its possible origin is briefly discussed.
Notwithstanding the visible maturity of the subject of Bose-Einstein Correlations (BEC), as witnessed nowadays, we would like to bring to ones attention two points, which apparently did not received attention they deserve: the problem of the choice o
f the form of $C_2(Q)$ correlation function when effects of partial coherence of the hadronizing source are to be included and the feasibility to model effects of Bose-Einstein statistics, in particular the BEC, by direct numerical simulations.
We demonstrate that selection of the minimal value of ordered variables leads in a natural way to its distribution being given by the Tsallis distribution, the same as that resulting from Tsallis nonextensive statistics. The possible application of t
his result to the multiparticle production processes is indicated.
