A sufficient condition for the existence of a “dead zone” for solutions of degenerate semilinear parabolic equations and inequalities

We consider the solutions of degenerate parabolic equations and inequalities of the form $Lu-u_t=|u|^q\operatorname{sgn}u$ and $\operatorname{sgn}u(Lu-u_t)-|u|^q\ge0$, $0<q<1$, with the elliptic operator $L$ in divergent or nondivergent form. We establish a dependence of the maximum modulus of the solution on the domain and on the equation (inequality) such that this dependence guarantees the existence of a “dead zone” of the solution. In this case, the character of degeneracy is unessential.