摘要：
将二阶微分方程边值问题推广到n维二阶微分系统中,并研究n维二阶微分系统在权函数变号的情况下正解的存在性.首先,将二阶微分系统转化成与原微分系统等价的积分系统;其次,根据得到的积分系统的具体表达式以及与其对应的格林函数的性质,构造适当的范数、锥和积分算子;最后,运用范数形式的锥拉伸与锥压缩不动点定理,结合微分系统中权函数变号的特点,对非线性项构造适当的条件,使其满足不动点定理,得到积分算子不动点的存在性,进而得到原微分系统正解的存在性.运用不动点定理,得到积分算子至少存在一个不动点,进而得到原二阶微分系统至少存在一个正解.原具变号权函数的二阶微分系统至少存在一个正解.%We extend the boundary value problem of second-order differential equation to n-dimensional second-order differential systems,and consider the existence of positive solutions for n-dimensional second-order differential system with indefinite weight function.Firstly,we transform the second-order differential system into integral system which equal to original differential system.Secondly,we construct suitable norm,cone and integral operator,according to the specific form of integral system and the properties of Green's function.Finally,using the fixed-point theorem of cone expansion and compression of norm type,and combining the characteristics of the indefinite weight function,we construct appropriate conditions of the nonlinear term,such that the fixed-point theorem is satisfied.And we obtain the existence of the fixed point of the operator,and then the existence of the positive solutions of original differential system is obtained.Using the fixed point theorem,we obtain that there is at least one fixed point of the integral operator,and then there is at least one positive solution to original second-order differential system.There is at least one positive solution for original second-order differential system with indefinite weight function.
