This academic dissertation is concerned about the application of doubling lemma and monotonicity formula for elliptic equations.There are many nonexistence results of positive solution of quasilinear el-liptic systems with m-Laplacians.According to the Liouville theorems of those systems on Rn,we obtain the singularity estimates of the positive C1-weak so-lutions on bounded or unbounded domain(but it is not Rn)and their decay rates on the exterior domain when |x|?oo.The doubling lemma which is developed by Polacik-Quittner-Souplet plays a key role here.In addition,the corresponding results of several special examples are presented.Next,we consider the nonexistence of positive stable solutions of a weight-ed Lane-Emden equation.First we obtain a monotonicity formula by choosing a proper energy.Based on this result,we prove that the nonnegative homogeneous stable solution must be a trivial solution.Finally,we prove the nonexistence of positive stable solutions when p? P+(n,?),where P+(n,?)is the Joseph-Lundgren exponent. |