自然科学版
陕西师范大学学报(自然科学版)
数学与计算机科学
关于Banach空间中p阶框架
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曹怀信1,李莉1,刘琴1,吴启斌2
(1 陕西师范大学 数学与信息科学学院, 陕西 西安 710062;2 咸阳师范学院 数学系, 陕西 咸阳 712000)
曹怀信,男,教授,博士研究生导师,主要从事算子理论与小波分析研究
摘要:
引入并研究了Banach空间X中的p阶Bessel列、 p阶框架、 p阶独立框架、 p阶紧框架与p阶Riesz基. 证明了:X中全体p阶Bessel列构成一个Banach空间BpX, X中的任一序列f={fn}n∈Λ是p阶Bessel列当且仅当c>0使得{cn}∈lq有‖∑n∈Λcnfn‖≤c‖{cn}‖q ,空间BpX与算子空间B(X*, lp)是等距线性同构的.应用算子论方法,证明了p阶Bessel列f={fn}n∈Λ是p阶框架当且仅当算子Tf是下有界的,它是独立的当且仅当算子Tf是可逆的, 以及独立的p阶框架与p阶Riesz基是一致的. 最后,证明了Banach空间X具有p阶Riesz基当且仅当存在X上与原有范数等价的范数‖·‖0,使得(X,‖·‖0)等距同构于lq .
关键词:
Banach空间; p阶Bessel列; p阶框架; p阶Riesz基
收稿日期:
2009-06-05
中图分类号:
O177.1
文献标识码:
A
文章编号:
1672-4291(2009)06-0005-06
基金项目:
国家自然科学基金资助项目(10571113,10871224)
Doi:
Frames of order p for a Banach space
CAO Huai-xin1, LI Li1, LIU Qin1, WU Qi-bin2
(College of Mathematics and Information Science, Shaanxi Normal University, Xi′an 710062, Shaanxi, China;2 Department of Mathematics, Xianyang Teacher′s College, Xianyang 712000, Shaanxi, China)
Abstract:
Bessel sequences, frames, tight frames,independent frames and Riesz basis of order p for a Banach space X are introduced and discussed. It is proved that the set BpX Bessel sequences of order p in X is a Banach space; it is established that a sequence f = {fn}n∈Λ in X is a Bessel sequence of order p if and only if c>0 such that ‖∑n∈Λcnfn‖≤c‖{cn}‖q for all {cn}∈lq, where p-1+q-1=1; it is also proved that the spaces BpX and B(X*, lp) are linearly and isometrically isomorphic. In light of operator theory, it is shown that a Bessel sequence f in X is a frame of order p for X if and only if the operator Tf is bounded below, and it is a Riesz basis of order p for X if and only if Tf is invertible. Moreover, it is proved that independent frames of order p and Riesz bases of order p for X are the same. Lastly, it is shown that a Banach space X has a Riesz basis of order p if and only if there exists a norm ‖·‖0 equivalent to the original norm of X such that (X,‖·‖0) is isometrically isomorphic to lq.
KeyWords:
Banach space; Bessel sequence of order p; frame of order p; Riesz basis of order p