Abstract
We are concerned with differential inequalities of the form -[d(M2)(y(0), y)](2 rho 2 )delta(M1)u - [d(M1)(x(0), x)](2 rho 1 )delta(M2)u >= V|u|(p) in M-1 x M-2, where M-i (i = 1, 2) are complete noncompact Riemannian manifolds, (x(0), y(0)) is an element of M-1 x M-2 is fixed, d(M1) (x(0), middot) is the distance function on M-1, d(M2) (y(0), middot) is the distance function on M-2, delta(Mi )is the Laplace-Beltrami operator on M-i, V = V (x, y) > 0 is a measurable function, and p > 1. Namely, we establish necessary conditions for existence of nontrivial weak solutions to the considered problem. The obtained conditions depend on the parameters of the problem as well as the geometry of the manifolds M-i. Next, we discuss some special cases of potential functions V. The proof of our main result is based on the nonlinear capacity method and a result due to Bianchi and Setti (2018) about the construction of cut-off functions with controlled gradient and Laplacian, under certain assumptions on the Ricci curvatures of the manifolds.