Fujita phenomena in nonlinear fractional Rayleigh–Stokes equations

This paper concerns the Cauchy problems for the nonlinear Rayleigh–Stokes equation and the corresponding system with time-fractional derivative of order [Formula: see text], which can be used to simulate the anomalous diffusion in viscoelastic fluids. It is shown that there exists the critical Fujita exponent which separates systematic blow-up of the solutions from possible global existence, and the critical exponent is independent of the parameter [Formula: see text]. Different from the general scaling argument for parabolic problems, the main ingredients of our proof are suitable decay estimates of the solution operator and the construction of the test function.