Multiple solutions to a Neumann problem with equi-diffusive reaction term
Multiple solutions to a Neumann problem with equi-diffusive reaction term
The existence of four solutions, one negative, one positive, andtwo sign-changing (namely, nodal), for a Neumann boundary-valueproblem with right-hand side depending on a positive parameter isestablished. Proofs make use of sub- and super-solution techniquesas well as Morse theory.