Upper and lower solutions for systems of second order equations with nonnegative characteristic form and discontinuous nonlinearities

Abstract

On considere des systemes de la forme −L 2 [u 2 ]=f r (x, u) dans Ω, r=1, ..., m ou Ω⊆R est un domaine borne lisse, u=(u 1 , ..., u m ) et L 2 [u]= n i,j ∑ =1 a ij r (x)u xd i xd j+∑ i=1 n b i 2 (x)u xd i+C 2 (x)u