The cause for emergence of irreversibility

Abstract

Investigation of the cause for emergence of irreversibility in kinetic equations for pair distribution functions and equations of multimoment hydrodynamics they yield in a gas of particles with internal structure is performed. It is established that irreversibility appears at the initial stage of modeling. The cause is the semi-classical approximation that is used for interpretation of passing the particles interaction domain. After transition to kinetic and hydrodynamic stages of gas modeling initial conditions lose the information about direction of system evolution, and this information is fully concentrated in equations of kinetics and hydrodynamics. The irreversibility of equations becomes responsible for direction of system evolution. The action responsible for the translation of information on evolution direction from the initial conditions to resulting equations is specified. It is the replacing the exact distribution function by its average over impact parameters of colliding particles. Replacing made at the entrance to particles interaction domain leads to direct equations of kinetics and hydrodynamics. Replacing made at the exit from particles interaction domain leads to reverse equations of kinetics and hydrodynamics. Both the direct and reverse equations of multimoment hydrodynamics are necessary for interpreting the behavior of unstable systems.