单位球上再生核Hilbert空间的次正规性

徐宪民

数学学报 ›› 2014, Vol. 57 ›› Issue (2) : 249-260.

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数学学报 ›› 2014, Vol. 57 ›› Issue (2) : 249-260. DOI: 10.12386/A2014sxxb0025
论文

单位球上再生核Hilbert空间的次正规性

    徐宪民
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Subnormality of the Reproducing Kernel Hilbert Spaces on the Unit Ball

    Xian Min XU
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文章历史 +

摘要

在Cd中,由函数gz)= ∑n=0anznan≥0)生成的解析Hilbert空间HdgBdR)是酉不变的再生核Hilbert空间. 本文证明了,当d≥ 2时,若sup{anRn}<+∞,则有球代数ABdR)中的函数fM,即HdgBdR)上的乘子代数MHBdR)的真子集. 由此可知,若存在M > 0,使得0 ≤ a0a1 ≤ … ≤ Mn = 0,1,2,…,则HdgBdR)不是次正规的.因而不存在Cd中的正测度μ,使得对任何fHdgBdR)||f||Hdg2 = ∫Cd |f|(z)|2(z),而且在HdgBdR)上的von Neumann不等式不成立.

Abstract

Let Bd be the unit ball ofd-dimensional complex Euclid space Cd, Hdg (BdR) the reproducing kernel Hilbert space with U-invariant reproducing kernel K(z,w) = g(<z,w>), where g(z) = ∑n=0 anzn (an ≥ 0) is the generating function of the space Hdg (BdR). In this paper, we show that the multiplier algebra of the space Hdg (BdR) is a proper subset of H(BdR), and there exists a holomorphic self-mapping ø from BdRinto BdRsuch that the multiplication operator Møis not bounded when the sequence {an}n=0 is bounded andd ≥ 2. Furthermore, we prove that if the coefficients sequence {an}n=0 of the generating function g is a bounded, non-decreasing sequence, i.e. there exists a positive number M such that 0 ≤ a0a1 ≤ … ≤ M, n = 0, 1, 2, …, then the space Hdg (BdR) is not subnormal, in other words, there is not any positive measure μ on Cd such that ||f|| Hdg2 =∫ Cd |f(z)|2(z), for each fHdg (BdR), and then von Neumann's inequality does not hold on the space Hdg (BdR).

关键词

再生核Hilbert空间 / 复合算子 / 乘子 / 次正规性 / von Neumann不等式

Key words

reproducing kernel Hilbert space / multiplier / composition operator / subnormality / von Neumann's inequality

引用本文

导出引用
徐宪民. 单位球上再生核Hilbert空间的次正规性. 数学学报, 2014, 57(2): 249-260 https://doi.org/10.12386/A2014sxxb0025
Xian Min XU. Subnormality of the Reproducing Kernel Hilbert Spaces on the Unit Ball. Acta Mathematica Sinica, Chinese Series, 2014, 57(2): 249-260 https://doi.org/10.12386/A2014sxxb0025

参考文献

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[3] Conway B., Submormal Operators, Pitman Advanced Publishing Program, Boston, London, Melbourne, 1981.
[4] Guo K., Hu J., Xu X., Toeplitz algebra, subnormal tuples and rigidity or reproducing C[z1, …, zd]-modules, J. Funct. Aral., 2004, 210: 224-247.
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[7] Xu X. M., Operator Theory on Hilbert Modules with Unitary Invariant Reproducing Kernel, Dissertation for PH.D., Fudan University, Shanghai, 2004.
[8] Xu X. M., Composition Operator Theory, Science Press, Beijing, 1999.

基金

浙江省自然科学基金资助项目(Y6110824);浙江省重点学科“基础数学”建设经费资助项目
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