An (not necessarily unital) operator system is a self-adjoint subspace of , equipped with the induced matrix norm and the induced matrix cone. We say that an operator system is dualizable if one can find an equivalent dual matrix norm on the dual space such that under this dual matrix norm and the canonical dual matrix cone, becomes a dual operator system.
We show that an operator system is dualizable if and only if the ordered normed space satisfies a form of bounded decomposition property. In this case,
is the largest dual matrix norm that is equivalent to and dominated by the original dual matrix norm on that turns it into a dual operator system, denoted by . It can be shown that is again dualizable.
For every completely bounded completely positive map between dualizable operator systems, there is a unique weak-*-continuous completely bounded completely positive map that is compatible with the dual map . From this, we obtain a full and faithful functor from the category of dualizable operator systems to that of dualizable dual operator systems.
Moreover, we will verify that that if is either a C*-algebra or a unital operator system, then is dualizable and the canonical weak-*-homeomorphism from the unital operator system to the operator system is a completely isometric complete order isomorphism.
Furthermore, via the duality functor above, the category of C*-algebras and that of unital operator systems (both equipped with completely positive complete contractions as their morphisms) can be regarded as full subcategories of the category of dual operator systems (with weak-*-continuous completely positive complete contractions as their morphisms).
Consequently, a nice duality framework for operator systems is obtained, which includes all C*-algebras and all unital operator systems.
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吴志强,南开大学陈省身数学研究所教授、博士生导师。主要研究方向为算子代数和泛函分析,先后在Proceedings of the London Mathematical Society, Journal of Functional Analysis, Mathematische Zeitschrift, Journal of Operator Theory等专业期刊上发表论文数十篇,2005年入选教育部新世纪优秀人才支持计划,先后主持完成国家自然科学基金面上项目4项,目前正主持国家自然科学基金面上项目1项。