Hermann Pfitzner, Georg Schluechtermann
We prove that in the setting of operator spaces the result of Davis, Figiel, Johnson and Pelczynski on factoring weakly compact operators holds accordingly. Though not related directly to the main theorem we add a remark on the description of weakly compact subsets in the dual of noncommutative vector valued ${\rm L}_1$.
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We prove quantitative factorization results for several classes of operators, including weakly compact, Rosenthal, and $ξ$-Banach-Saks operators.
Generalized b-weakly compact operators and their factorization through KR-spaces
本文研究了广义b-弱紧致算子的性质，并通过引入KR空间来探讨其分解问题。
We prove a basic property of continuous multilinear mappings between topological vector spaces, from which we derive an easy proof of the fact that a multilinear mapping (and a polynomial) between topological vector spaces is weakly continuous on weakly bounded sets if and only if it is weakly {\it uniformly\/} continuous on weakly bounded sets. This result was obtained in 1983 by Aron, Hervés and Valdivia for polynomials between Banach spaces, and it also holds if the weak topology is replaced by a coarser one. However, we show that it need not be true for a stronger topology, thus answering …
$k$-Regular Factorizations and Joint Invariant Subspaces of Completely Non-Coisometric Row Contractions
研究完全非等距行压缩的特征函数的$k$-正则分解，建立联合不变子空间链与$k$-正则分解的一一对应，并给出函数模型和块上三角分解。
Let $(M,Γ)$ be a Hopf--von Neumann algebra, so that $M_\ast$ is a completely contractive Banach algebra. We investigate whether the product of two elements of $M$ that are both weakly almost periodic functionals on $M_\ast$ is again weakly almost periodic. For that purpose, we establish the following factorization result: If $M$ and $N$ are injective von Neumann algebras, and if $x, y \in M \bar{\otimes} N$ correspond to weakly compact operators from $M_\ast$ to $N$ factoring through reflexive operator spaces $X$ and $Y$, respectively, then the operator corresponding to $xy$ factors through th…
$k$-Regular Factorizations and Invariant Subspaces of Completely Non-Unitary Contractions
引入压缩算子的$k$-正则分解概念，建立其与完全非酉压缩的不变子空间链之间的一一对应，并构造显式泛函模型，同时引入交换$k$-压缩的对称$k$-正则元组，证明经典反例不满足该性质。
A bounded linear operator between Banach spaces is called {\it completely continuous} if it carries weakly convergent sequences into norm convergent sequences. Isolated is a universal operator for the class of non-completely-continuous operators from $L_1$ into an arbitrary Banach space, namely, the operator from $L_1$ into $\ell_\infty$ defined by $$ T_0 (f) =\left( \int r_n f \, dμ\right)_{n\ge 0} \ , $$ where $r_n$ is the $n^{\text{th}}$ Rademacher function. It is also shown that there does not exist a universal operator for the class of non-completely-continuous operators between two arbit…
In this paper, we completely characterize the finite rank commutator and semi-commutator of two monomial-type Toeplitz operators on the Bergman space of certain weakly pseudoconvex domains. Somewhat surprisingly, there are not only plenty of commuting monomial-type Toeplitz operators but also non-trivial semi-commuting monomial-type Toeplitz operators. Our results are new even for the unit ball.%The situation is different from the case of unit disk. %Our results extend several known results using completely different arguments. Some interesting higher-dimensional phenomena appear on the unit p…
Given a pair of self-adjoint-preserving completely bounded maps on the same $C^*$-algebra, say that $φ\leq ψ$ if the kernel of $φ$ is a subset of the kernel of $ψ$ and $ψ\circ φ^{-1}$ is completely positive. The \emph{Agler class} of a map $φ$ is the class of $ψ\geq φ.$ Such maps admit colligation formulae, and, in Lyapunov type situations, transfer function type realizations on the Stinespring coefficients of their Wittstock decompositions. As an application, we prove that the support of an extremal Wittstock decomposition is unique.
A theorem of Davis, Figiel, Johnson and Pełczyński tells us that weakly-compact operators between Banach spaces factor through reflexive Banach spaces. The machinery underlying this result is that of the real interpolation method, which has been adapted to the category of operator spaces by Xu, showing the this factorisation result also holds for completely bounded weakly-compact maps. In this note, we show that Xu's ideas can be adapted to give an intrinsic characterisation of when a completely contractive Banach algebra arises as a closed subalgebra of the algebra of completely bounded opera…
The framework of the paper is that of the full Fock space ${\Cal F}^2({\Cal H}_n)$ and the Banach algebra $F^\infty$ which can be viewed as non-commutative analogues of the Hardy spaces $H^2$ and $H^\infty$ respectively. An inner-outer factorization for any element in ${\Cal F}^2({\Cal H}_n)$ as well as characterization of invertible elements in $F^\infty$ are obtained. We also give a complete characterization of invariant subspaces for the left creation operators $S_1,\cdots, S_n$ of ${\Cal F}^2({\Cal H}_n)$. This enables us to show that every weakly (strongly) closed unital subalgebra of $\{…
Let $X$ be a Banach space, $Σ$ be a $σ$-algebra, and $m:Σ\to X$ be a (countably additive) vector measure. It is a well known consequence of the Davis-Figiel-Johnson-Pelczýnski factorization procedure that there exist a reflexive Banach space $Y$, a vector measure $\tilde{m}:Σ\to Y$ and an injective operator $J:Y \to X$ such that $m$ factors as $m=J\circ \tilde{m}$. We elaborate some theory of factoring vector measures and their integration operators with the help of the isometric version of the Davis-Figiel-Johnson-Pelczýnski factorization procedure. Along this way, we sharpen a result of Okad…
We investigate weak amenability of the Banach algebra A(X) of approximable operators on a Banach space X and its relation to factorization properties of operators in A(X). We show that if A(X) is weakly amenable, then either A(X) is self-induced (a nice factorization property), or X is very special, combining some of the exotic properties of the spaces of Gowers and Maurey and of Pisier. In the class of self-induced Banach algebras we show that weak amenability is preserved under an equivalence of Morita type. Using this we extend some results of A. Blanco about weak amenability of A(X).
Approximate factorization properties for operator systems
本文证明算子系统张量积层次中的多种核性性质可表示为近似因子分解性质，推广了Choi-Effros的C*-代数完全正逼近性质及Han-Paulsen的算子系统核性性质。
Factorization Property in Rearrangement Invariant Spaces
本文研究了重排不变 Haar 系统空间中的因子分解性质，证明了具有大对角线的有界算子近似为某对角算子的因子，并在 Haar 系统作为无条件基时确立其因子分解性质。
Grothendieck's inequalities for operators and bilinear forms imply some factorization results for complex m x n matrices. Based on the theory of operator spaces and completely bounded mappings we present norm optimal versions of these results and two norm optimal factorization results related to the Schur product. We show that the spaces of respectively bilinear forms and Schur multipliers are conjugate duals to each other with respect to their completely bounded norms.
Weakly $\mathcal U(d)$-homogeneous commuting tuple of bounded operators
本文研究了弱 $\mathcal U(d)$-齐次交换元算子组，证明了多移位与 $\mathcal U(d)$-齐次多移位的等价性，并细化了球形平衡多移位的结果。
To each finite-dimensional operator space $E$ is associated a commutative operator algebra $UC(E)$, so that $E$ embeds completely isometrically in $UC(E)$ and any completely contractive map from $E$ to bounded operators on Hilbert space extends uniquely to a completely contractive homomorphism out of $UC(E)$. The unit ball of $UC(E)$ is characterized by a Nevanlinna factorization and transfer function realization. Examples related to multivariable von Neumann inequalities are discussed.
We completely characterize connected Lie groups all of whose countable subgroups are weakly amenable. We also provide a characterization of connected semisimple Lie groups that are weakly amenable. Finally, we show that a connected Lie group is weakly amenable if the group is weakly amenable as a discrete group.
For an $m \times n$ complex matrix $X$ of rank $r$ with Schur multiplier $S_X$ we show that there exist an $ r \times m $ complex matrix $L$ and an $ r\times n $ complex matrix $R$ such that $X = L^*R$ and $\|S_X\|\, =\, \|\mathrm{diag} (L^*L) \|^{\frac{1}{2}} \| \mathrm{diag} (R^*R) \| ^{\frac{1}{2}},$ and the norm condition is optimal. Let the completely bounded norm of the bilinear form $B_X$ induced by $X$ on $(\mathbb{C}^m, \|.\|_\infty) \times (\mathbb{C}^n, \|.\|_\infty)$ be denoted $\|B_X\|_{cb},$ then $X$ has a factorization $ X = Δ(η)^* C Δ(ξ)$ with $η$ in $\mathbb{C}^m,$ $ξ$ in $\ma…
Jordan norms for multilinear maps on C*-algebras and Grothendieck's inequalities
该研究提出C*-代数上多重线性映射完全有界范数的推广形式Jordan范数，通过映射分解定义，并证明C*-代数对上的有界双线性型均为Jordan有界，且其Jordan范数不超过原范数的两倍。
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