| In this paper,the existence of solutions to two types of nonlinear partial differential equations is studied.On the one hand,we divided variational problems into three categories by spectra of operator A,and for a class of complex cases of σe(A)≠?,we used saddle point reduction and the index pair(iA0(B),νA0(B))to obtain some critical point theorems for abstract operator equations without compactness assumption,and proved the existence of the following periodic solutions of one-dimensional wave equations.where T>0,S1:=R/TZ,f:[0,π]×S1×R→R.On the other hand,we considered the following semi-linear Schrodinger equation using the relative Morse index.We developed the concept of Maslov type index(μ(M),υ(M))for(4-1)by the relative Fredholm index theory,and displayed the relationship with other index Theories,obtained the existence of nontrivial solutions of(4-1). |