FRW cosmological models with integrable and nonintegrable differential   equations of state
  The basic models of modern cosmology work in FRW spacetime. Hence follows that it is important to study the physical and mathematical nature of FRW cosmological models. In this work, we consider FRW models with the differential equations of state. Some new classes integrable and nonintegrable FRW cosmological models were constructed. It is remarkable that all proposed integrable and nonintegrable FRW models admit exact solutions. For some of them, such exact solutions are presented. Some artificial two-dimensional FRW models were also proposed. Finally in Appendix, we extend the obtained results for g-essence models and for its two reductions: k-essence and f-essence. 
Shynaray Myrzakul, Kuralay Esmakhanova, Kairat Myrzakulov, Gulgasyl   Nugmanova, Ratbay Myrzakulov
physics.gen-ph