目的研究Hilbert空间中Bessel列的算子扰动。方法运用算子理论。结果对于Hilbert空间H中的一个序列f={fi}i=1^∞及算子列{Tj^(i))i,j=1^∞包含B(H,K),给出使得{∞∑j=1 Tj^(i)fj)i=1^∞成为K中的Bessel序列的一些充分条件;证明了如果{Ti}i=1^∞包含B(H,K)使得Ti=T(i〉N0)且f={fi}i=1^∞是H中的Bessel列,则{Tifi}i=1^∞是K中的Bessel列。结论在一定的条件下,Hilbert空间中的Bessel列经过算子扰动,还可以是Bessel列。
Aim Some operator perturbations of Bessel sequences in a Hilbert space were discussed. Methods The operator theory was used. Results For a sequence f={fi}i=1^∞ in a Hilbert space H and an operator sequence {{Tj^(i))i,j=1^∞ belong to B(H,K), some sufficient conditions for the sequence {∞∑j=1 Tj^(i)fj)i=1^∞ to be a Bessel sequence in K are given. It is proved that the sequence {Tifi}i=1^∞ is a Bessel sequence in K if a sequence {Ti}i=1^∞ belong to B(H,K) can make Ti = Tfor all i 〉 N0 and f = {fi}i=1^∞ is a Bessel sequence in H. Conclusion A Bessel sequence in a Hilbert space after operator perturbation can still be a Bessel sequence under certain conditions.