×

Lyapunov theorems for operator algebras. (English) Zbl 0769.46036

Mem. Am. Math. Soc. 458, 88 p. (1991).
Lyapunov’s theorem states that the range of a nonatomic vector-valued measure (with values in \(\mathbb{C}^ n\)) is a compact convex set. The volume under review contains a comprehensive study of generalizations of Lyapunov’s result in the following form. Let \(\Psi\) be an affine map of a convex set \(Q\) in a linear space \(X\) into another linear space \(Y\). By a theorem of Lyapunov’s type the authors mean that for each \(x\in Q\) there is an extreme point \(e\in Q\) such that \(\Psi(e)\) is close to \(\Psi(x)\). In the typical case \(X\) is a von Neumann algebra, \(Q\) is a weak\(^*\) closed face and \(Y\) is \(\mathbb{C}^ n\) or \(M_ n(\mathbb{C})\). When the range space is noncommutative (i.e., a matrix algebra) the analysis is much harder and the authors make several conjectures.
Reviewer: D.Petz (Budapest)

MSC:

46L05 General theory of \(C^*\)-algebras
46G10 Vector-valued measures and integration
46A55 Convex sets in topological linear spaces; Choquet theory
46L30 States of selfadjoint operator algebras
46L10 General theory of von Neumann algebras
28B05 Vector-valued set functions, measures and integrals
46B99 Normed linear spaces and Banach spaces; Banach lattices
93B03 Attainable sets, reachability
52A20 Convex sets in \(n\) dimensions (including convex hypersurfaces)
60A10 Probabilistic measure theory
93C15 Control/observation systems governed by ordinary differential equations
Full Text: DOI