不变子空间

It is to ask whether every bounded linear operator on a separable Hilbert space has a nontrivial invariant subspace and it can be reduced to the case of diagonal operator.

不变子空间问题是一个引人瞩目的公开问题，它是说在一个可分的Hilbert空间上是否每一个有界线性算子都存在非平凡的不变子空间？

Although many results have been obtained, there are still a number of very interesting questions about composition operators unsolved. There is much more to be learned about the collective compactness and convergence of composition operator sequences, compactness of various product of composition operators, cyclicity, closed range and spectra of composition operators in various settings. Commutants of composition operators seem to be very difficult to characterize. Only a little is known about their reducing invariant subspaces. There has been no work on C〓 algebras generated by composition operators.

尽管已取得如此丰富的结果，但是关于复合算子仍然有大量非常有意义的问题值得研究，例如：复合算子序列的总体紧性及收敛性、复合算子的各种乘积的紧性、复合算子的闭值域问题、复合算子在各种解析函数空间上的谱的描述、换位复合算子的刻画、复合算子诱导的不变子空间问题、循环复合算子的研究、由复合算子生成的C〓-代数的研究、不同解析函数空间之间的加权复合算子及复合算子半群等等问题。

Quasi-invariant subspaces similar to the quasi-invariant subspace generated by z+w are completely depicted.

给出了和z+w生成的拟不变子空间相似的拟不变子空间的完全刻画。

In particular, the paper gives a new description of the largest simultaneous invariant subspace contained in a given subspace H.

特别对 包含在给定子空间H中的最大同时不变子空间给出了新的描述。

The well-known invariant subspace problem is A long-standing problem in operator theory,which has been to determine whether every operator $T$ on a Banach space $X$ must have a nontrivial invariant subspace.

不变子空间问题是一个尚未解决的问题， Enflo反例所给出的没有不变子空间的算子不为任何算子的共轭。

Secondly, the concept of column space, cyclic invariant subspace and generalized cyclic invariant subspace were introduced.And some basic properties, such as separation lemma, were presented.

其次，引入列空间、循环不变子空间和广义循环不变子空间等基本几何概念，给出一些有关概念的基本性质，特别是分离引理。

Equivalently, it can be raised as follows: for an A operator T, if M and N are two invariant subspaces of T satisfying N include M and dimN/M=∞, then does there exist another invariant subspace L such that N include L, and L include M ? It is rather difficult to study the invariant subspace problem of general diagonal operators.

研究表明它可以约化为对角算子的不变子空间的情形，具体地它有如下的等价提法：对于A算子算T，，如果M和N是T的两个不变子空间，满足且dimN/M=∞，那么是否存在T的另一个不变子空间L使得M包含于L，且L包含于N？

It is proved that every Lie derivation of nest algebra is the sum of an associative derivation and a general trace. Every Lie isomorphism between nest subalgebras of a factor von Neumann algebra is the sum of an isomorphism and a general trace or the sum of a negative anti-isomorphism and a general trace. Lie invariant subspace of linear mappings on Banach algebras is introduced, and linear maps from nest subalgebra of a factor von Neumann algebra into itself which satisfy the property that the space of derivations is their Lie invariant subspaces are characterized. Simultaneously, it is shown that such maps are Lie derivations modulo the set of scalar multiple of the identity.

得到Lie导子的特征表示，即套代数上的任何一个Lie导子都是内导子与广义迹之和；给出了Lie同构和同构及反同构之间的关系，即因子von Neumann代数中套子代数之间的任何一个Lie同构要么是同构与广义迹之和要么是负反同构与广义迹之和；引入了Banach代数上线性映射的Lie不变子空间，并给出von Neumann代数中套子代数上以导子空间为Lie不变子空间的线性映射的一个刻画，同时也表明在模去数乘恒等映射的意义下，以导子空间为Lie不变子空间的线性映射就是Lie导子。

This paper mainly deals with invariant subspaces and cyclic vectors of certain diagonal operators on a separable Hilbert space. In this case, a complete characterization is given.

考虑一般对角算子的不变子空间是非常困难的，本文主要研究Hilbert空间上一类对角算子的不变子空间和循环向量，给出了这类算子不变子空间和循环向量的完整刻画。

By using the circular invariant characteristic of the defined subspaces,a necessary condition on complete reachability is g...

利用所定义的子空间是循环不变子空间的特点，得到了切换线性奇异系统能达的必要条件。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。