研究了Drazin可逆算子在0点的特征投影,得到了两个结果:设A是Drazin可逆的,则Q=A^π的充要条件是Q^2=Q,AQ=QA,σ(AQ)={0}且A+Q是可逆的;设E是与A可交换的幂等算子,A是Drazin可逆的且i(A)=k,那么下列条件是等价的:E是A在0点的特征投影;对所有的λ≠0,A+λE是可逆的;A^kE=0且对某个ξ≠0,A+ξE是可逆的.
Eigenprojections at zero of Drazin invertible operators on a Hilbert space are studied. Two results are obtained. The first result is that if A is a Drazin invertible operator, then Q = A^π if and only if Q^2= Q, AQ = QA, σ(AQ) - {0} and A + Q is invertible. The second one is that if E is an idempotent operator commuting with A and A is Drazin invertible with i (A) k, then the following three statements are equivalent: E is the eigenprojection of A at 0; A + λE is invertible for all λ≠0; A^kE = 0 and A + ξE is invertible for some ξ≠0.