B-convex operator spaces

Boundary representations of operator spaces, and compact rectangular matrix convex sets

We initiate the study of matrix convexity for operator spaces. We define the notion of compact rectangular matrix convex set, and prove the natural analogs of the Krein-Milman and the bipolar theorems in this context. We deduce a canonical correspondence between compact rectangular matrix convex sets and operator spaces. We also introduce the notion of boundary representation for an operator space, and prove the natural analog of Arveson's conjecture: every operator space is completely normed by its boundary representations. This yields a canonical construction of the triple envelope of an ope…

Operator convexity in Krein spaces

We introduce the notion of Krein-operator convexity in the setting of Krein spaces. We present an indefinite version of the Jensen operator inequality on Krein spaces by showing that if $(\mathscr{H},J)$ is a Krein space, $\mathcal{U}$ is an open set which is symmetric with respect to the real axis such that $\mathcal{U}\cap\mathbb{R}$ consists of a segment of real axis and $f$ is a Krein-operator convex function on $\mathcal{U}$ with $f(0)=0$, then \begin{eqnarray*} f(C^{\sharp}AC)\leq^{J}C^{\sharp}f(A)C \end{eqnarray*} for all $J$-positive operators $A$ and all invertible $J$-contractions $C…

Estimates of operator convex and operator monotone functions on bounded intervals

Recently the behavior of operator monotone functions on unbounded intervals with respect to the relation of strictly positivity has been investigated. In this paper we deeply study such behavior not only for operator monotone functions but also for operator convex functions on bounded intervals. More precisely, we prove that if $f$ is a nonlinear operator convex function on a bounded interval $(a,b)$ and $A, B$ are bounded linear operators acting on a Hilbert space with spectra in $(a,b)$ and $A-B$ is invertible, then $sf(A)+(1-s)f(B)>f(sA+(1-s)B)$. A short proof for a similar known result con…

非交换凸集的一个延拓性质与算子系统的对偶性

An extension property for noncommutative convex sets and duality for operator systems

本文刻画了紧致非交换凸集满足连续仿射函数一致延拓性质的包含关系，由此给出可对偶化算子系统的几何刻画，并建立其永久性质及新例子。

有界算子有界凸集的分离定理

Separation theorems for bounded convex sets of bounded operators

本文在有界算子的凸集闭包上建立新的度量刻画，并应用于优超理论。

Absorbing representations with respect to closed operator convex cones

We initiate the study of absorbing representations of $C^\ast$-algebras with respect to closed operator convex cones. We completely determine when such absorbing representations exist, which leads to the question of characterising when a representation is absorbing, as in the classical Weyl-von Neumann type theorem of Voiculescu. In the classical case, this was proven by Elliott and Kucerovsky who proved that a representation is nuclearly absorbing if and only if it induces a purely large extension. By considering a related problem for extensions of $C^\ast$-algebras, which we call the purely …

Operator systems and convex sets with many normal cones

The state space of an operator system of $n$-by-$n$ matrices has, in a sense, many normal cones. Merely this convex geometrical property implies smoothness qualities and a clustering property of exposed faces. The latter holds since each exposed face is an intersection of maximal exposed faces. An isomorphism translates these results to the lattice of ground state projections of the operator system. We work on minimizing the assumptions under which a convex set has the mentioned properties.

Exponentiation of Lie Algebras of Linear Operators on Locally Convex Spaces

Necessary and sufficient conditions for the exponentiation of finite-dimensional real Lie algebras of linear operators on complete Hausdorff locally convex spaces are obtained, focused on the equicontinuous case - in particular, necessary conditions for exponentiation to compact Lie groups are established. Applications to complete locally convex algebras, with special attention to locally C$^*$-algebras, are given. The definition of a projective analytic vector is introduced, playing an important role in some of the exponentiation theorems.