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arXiv math/0010271math.OA
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有限von Neumann algebra中n元组自伴算子的几何spectral theory:II

A geometric spectral theory for n-tuples of self-adjoint operators in a finite von Neumann algebra: II

Charles A. Akemann, Joel Anderson

摘要:

给定n元组{b_1,...,b_n}的有限von Neumann代数M中的自伴算子和M上的忠实正规迹态τ,定义了从M到R^{n+1}的映射Psi(a)=(τ(a),τ(b_1a),.,τ(b_na))。单位球在Psi下的正部分的像称为{b_1,.,b_n},并且由B表示。在Nik Weaver的前一篇论文中,我们证明了B的几何反映了算子{b_1,...,b_n}。例如,我们证明了B中的暴露面由{b_1,.,b_n}。在本文中,我们将这项研究扩展到没有暴露的面孔。我们用{b_1,...,b_n}和τ.我们还研究了凸,紧集,暴露在一个以上的超平面的支持面。虽然这项研究的许多结论涉及太多的符号,无法很好地放在摘要中,但有两个结果很好地体现了它们的味道。设N是由{b_1,...,b_n}和身份。定理6.1:如果B的极值点的集合是可数的,则N是阿贝尔的。推论5.6:B有有限个极值点当且仅当N是有限维的阿贝尔。

英文摘要:

Given an n-tuple {b_1, ..., b_n} of self-adjoint operators in a finite von Neumann algebra M and a faithful, normal tracial state tau on M, we define a map Psi from M to R^{n+1} by Psi(a) = (tau(a), tau(b_1a), ..., tau(b_na)). The image of the positive part of the unit ball under Psi is called the spectral scale of {b_1, .., b_n} relative to tau and is denoted by B. In a previous paper with Nik Weaver we showed that the geometry of B reflects spectral data for real linear combinations of the operators {b_1, .., b_n}. For example, we showed that an exposed face in B is determined by a certain pair of spectral projections of a real linear combination of {b_1, .., b_n}. In the present paper we extend this study to faces that are not exposed. We completely describe the structure of arbitrary faces of B in terms of {b_1, .., b_n} and tau. We also study faces of convex, compact sets that are exposed by more than one hyperplane of support. Although many of the conclusions of this study involve too much notation to fit nicely in an abstract, there are two results that give their flavor very well. Let N be the algebra generated by {b_1, ..., b_n} and the identity. Theorem 6.1: If the set of extreme points of B is countable, then N is abelian. Corollary 5.6: B has a finite number of extreme points if and only if N is abelian and finite dimensional.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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