Some new oscillation theorems for second order nonlinear elliptic equations with damping

In this paper, some new oscillation criteria are obtained for second order elliptic differential equations with damping of the form ∇ · A(x)∇y + BT (x)∇y + q(x)f (y) = 0, x∈ Ω, where Ω is an exterior domain in RN. These criteria are different from most known ones in the sense that they are based on a class of new functions of the form Φ(r, s, l) defined in the sequel. © 2006 Elsevier Inc. All rights reserved