设E和F是Banach空间,B(E,F)表示从空间E到F的有界线性算子全体。当A∈B(B,F)具有有界的广义逆A^+∈B(F,E)时,Nashed和Chen证明了一个很有用的定理:对任意满足||T-A||〈||A^+||^-1的T,若使C^-1(A,A^+,T)TN(A)CR(A),则B=A^+C^-1(A,A^+,T)是T的一个广义逆,且N(B)=N(A^+)和R(B)=R(A^+),其中C(A,A^+,T)=IF+(T-A)A^+,在这篇文章中,我们将上述结果推广到A不必具有有界广义逆的情形.并且我们证明这里的定理包含Nashed和Chen的定理.所以我们的结果推广了上述己知的定理.
Let E, F be Banach spaces, B(E, F) denote all the bounded linear operator from E to F, and A^+ be a generalized inverse of A. Nashed and Chen have proved a useful theorem: for all T satisfying ||T-A||〈||A^+||^-1,if C^-1(A,A^+,T)^TN(A)CR(A),then B=A^+C^-1(A,A^+,T) is a generalized inverse of T, and N(B) =N(A^+), R(B) = R(A^+), where C(A, A^+, T) = IF+(T-A)A^+.In this paper, we consider the case of A^+ need it to be bounded. Let A∈B(E, F),and ^——R(A),N(A) split,F,E respectively,say F=^——R(A) N^and E=N(A)R^+.Let A^+:D(A^+)=R(A)+N^+→E be a generalized inverse of A corresponding to the decompositions above.The following result is proved that if T E B(E, F) satisfies N(T)∩R^+ ={0} , R(T) n N(A^+)={0} and TR(A^+) = R(T), then B=A^+C^-1(A,A^+,T):R(T)+N^+→E is a generalized inverse of T with N(B) = N(A^+) and R(B) = R(A^+). It is a generalization to the theorem by Nashed and Chen.