Nonexistence of sign-changing solutions for some elliptic and parabolic inequalities

We establish nonexistence of nontrivial solutions (including sign-changing ones) for some partial differential inequalities of elliptic and parabolic type containing nonlinear terms that depend on the positive and negative part of the sought function in different ways. Systems of elliptic inequalities with similar structure are also considered. The proofs are based on the test function method. © 2020 John Wiley & Sons, Ltd.