In this paper, we investigate the existence and stability of positive solutions for some nonlinear elliptic problems.In chapter 1, we study the symmetry of components of positive solutions for γ-Laplacian system where △γu= div(|â–½u|γ-2â–½u) with 1<γ< n, f, g:[0,+∞)â†'R is continuous satisfying the ’monotonicity’ assumptionIn chapter 2, we investigate the stability of solution for Schrodinger - Possion system where n≥ 3, p> 1, and we also give the Joseph-Lundgren(JL) exponent, which is important for the existence of stable solution.In chapter 3, we investigate the existence of positive stable solution and the sta-bility of singular solution for the fully nonlinear elliptic equation-k-Hessian equation with radial structure, where n≥3,1< k< n/2 and p> 1. Moreover, we obtain the JL exponent. |