On the predual of non-commutative $H^\infty$

Conditional expectation on non-commutative $H^{(r,s)}_{p}(\mathcal A;\ell_{\infty})$ and $H_{p}(\mathcal A;\ell_{1})$ spaces : semifinite case

In this paper we investigate the conditional expectation on the non-commutative $H^{(r,s)}_{p}(\mathcal A;\ell_{\infty})$ and $H_{p}(\mathcal A;\ell_{1})$ spaces associated with semifinite subdiagonal algebra, and prove the contractibility of the underlying conditional expectation on these spaces.

A weak-type inequality for non-commutative martingales and applications

We prove a weak-type (1,1) inequality for square functions of non-commutative martingales that are simultaneously bounded in $L^2$ and $L^1$. More precisely, the following non-commutative analogue of a classical result of Burkholder holds: there exists an absolute constant $K>0$ such that if $\cal{M}$ is a semi-finite von Neumann algebra and $(\cal{M}_n)^{\infty}_{n=1}$ is an increasing filtration of von Neumann subalgebras of $\cal{M}$ then for any given martingale $x=(x_n)^{\infty}_{n=1}$ that is bounded in $L^2(\cal{M})\cap L^1(\cal{M})$, adapted to $(\cal{M}_n)^{\infty}_{n=1}$, there exist…

Non-commutative martingale transforms

We prove that non-commutative martingale transforms are of weak type $(1,1)$. More precisely, there is an absolute constant $C$ such that if $\M$ is a semi-finite von Neumann algebra and $(\M_n)_{n=1}^\infty$ is an increasing filtration of von Neumann subalgebras of $\M$ then for any non-commutative martingale $x=(x_n)_{n=1}^\infty$ in $L^1(\M)$, adapted to $(\M_n)_{n=1}^\infty$, and any sequence of signs $(ε_n)_{n=1}^\infty$, $$\left\Vert ε_1 x_1 + \sum_{n=2}^N ε_n(x_n -x_{n-1}) \right\Vert_{1,\infty} \leq C \left\Vert x_N \right\Vert_1 $$ for $N\geq 2$. This generalizes a result of Burkholde…

Twisting non-commutative $L_p$ spaces

The paper makes the first steps into the study of extensions ("twisted sums") of noncommutative $L^p$-spaces regarded as Banach modules over the underlying von Neumann algebra $\mathcal M$. Our approach combines Kalton's description of extensions by centralizers (these are certain maps which are, in general, neither linear nor bounded) with a general principle, due to Rochberg and Weiss saying that whenever one finds a given Banach space $Y$ as an intermediate space in a (complex) interpolation scale, one automatically gets a self-extension $ 0\longrightarrow Y\longrightarrow X\longrightarrow …

Continuous model theories for von Neumann algebras

We axiomatize in (first order finitary) continuous logic for metric structures $σ$-finite $W^*$-probability spaces and preduals of von Neumann algebras jointly with a weak-* dense $C^*$-algebra of its dual. This corresponds to the Ocneanu ultrapower and the Groh ultrapower of ($σ$-finite in the first case) von Neumann algebras. We give various axiomatizability results corresponding to recent results of Ando and Haagerup including axiomatizability of $III_λ$ factors for $0<λ\leq 1$ fixed and their preduals. We also strengthen the concrete Groh theory to an axiomatization result for preduals of …

Non-commutative Stein inequality and its applications

The non-commutative Stein inequality asks whether there exists a constant $C_{p,q}$ depending only on $p, q$ such that \begin{equation*} \left\| \left(\sum_{n} |\mathcal{E}_{n} (x_n) |^{q}\right)^{\frac{1}{q}} \right\|_p \leq C_{p,q} \left\| \left(\sum_{n} | x_n |^q \right)^{\frac{1}{q}}\right \|_p\qquad \qquad (S_{p,q}), \end{equation*} for (positive) sequences $(x_n)$ in $L_p(\mathcal{M})$. The validity of $(S_{p,2})$ for $1 < p < \infty$ and $(S_{p,1})$ for $1 \leq p < \infty$ are known. In this paper, we verify (i) $(S_{p,\infty})$ for $1 < p \leq \infty$; (ii) $(S_{p,p})$ for $1 \leq p < …

Invariant means on subspaces of quantum weakly almost periodic functionals

Let $M$ be a Hopf--von Neuman algebra with the predual $M_*$ and $WAP(M)$ the subspace in $M$ composed of weakly almost periodic functionals on $M_*$. The main example of such an algebra is $M=L^\infty(\mathbb G)$ for a locally compact quantum group $\mathbb G$. We define a pair of left/right spaces $WAP_{iso,l}(M)$ and $WAP_{iso,r}(M)$ inside $WAP(M)$ and prove that they carry invariant means. These spaces are currently the widest known to admit invariant means in the quantum setting. In the case when $M=L^\infty(G)$ and $G$ is a locally compact group, these spaces are equal to $WAP(G)$.

An inequality for p-orthogonal sums in non-commutative ${\bf L_p}$

We give an alternate proof of one of the inequalities proved recently for martingales (=sums of martingale differences) in a non-commutative $L_p$-space, with $1<p<\infty$, by Q. Xu and the author. This new approach is restricted to $p$ an even integer, but it yields a constant which is $O(p)$ when $p\to \infty$ and it applies to a much more general kind of sums which we call $p$-orthogonal.

Extreme point methods in the study of isometries on certain non-commutative spaces

In this paper we characterize surjective isometries on certain classes of non-commutative spaces associated with semi-finite von Neumann algebras: the Lorentz spaces $L^{w,1}$, as well as the spaces $L^1+L^\infty$ and $L^1\cap L^\infty$. The technique used in all three cases relies on characterizations of the extreme points of the unit balls of these spaces. Of particular interest is that the representations of isometries obtained in this paper are global representations.

多项式增长的Banach代数类与有限个自由变量的$C^\infty$-函数的包络

Envelopes in the class of Banach algebras of polynomial growth and $C^\infty$-functions of a finite number of free variables

本文引入拓扑代数关于Banach代数类的包络概念，将多项式代数映到$C^\infty$-函数代数，并描述李代数泛包络、量子平面及量子$SL(2)$等代数的包络，证明自由结合代数包络在$k\le 2$时的结果。

Sums of commutators in ideals and modules of type II factors

Let M be a factor of type II_\infty or II_1 having separable predual and let M-bar be the algebra of affiliated τ-measureable operators. We characterize the commutator space [I,J] for sub-(M,M)-bimodules I and J of M-bar.

Hyperreflexivity of the space of module homomorphisms between non-commutative $L^p$-spaces

Let $\mathcal{M}$ be a von Neumann algebra, and let $0<p,q\le\infty$. Then the space $\Hom_\mathcal{M}(L^p(\mathcal{M}),L^q(\mathcal{M}))$ of all right $\mathcal{M}$-module homomorphisms from $L^p(\mathcal{M})$ to $L^q(\mathcal{M})$ is a reflexive subspace of the space of all continuous linear maps from $L^p(\mathcal{M})$ to $L^q(\mathcal{M})$. Further, the space $\Hom_\mathcal{M}(L^p(\mathcal{M}),L^q(\mathcal{M}))$ is hyperreflexive in each of the following cases: (i) $1\le q<p\le\infty$; (ii) $1\le p,q\le\infty$ and $\mathcal{M}$ is injective, in which case the hyperreflexivity constant is a…

The Mazur-Ulam property for commutative von Neumann algebras

Let $(Ω,μ)$ be a $σ$-finite measure space. Given a Banach space $X$, let the symbol $S(X)$ stand for the unit sphere of $X$. We prove that the space $L^{\infty} (Ω,μ)$ of all complex-valued measurable essentially bounded functions equipped with the essential supremum norm, satisfies the Mazur-Ulam property, that is, if $X$ is any complex Banach space, every surjective isometry $Δ: S(L^{\infty} (Ω,μ))\to S(X)$ admits an extension to a surjective real linear isometry $T: L^{\infty} (Ω,μ)\to X$. This conclusion is derived from a more general statement which assures that every surjective isometry …

Measurable Schur Multipliers and Completely Bounded Multipliers of the Fourier Algebras

Let G be a locally compact group L^p(G) be the usual L^p-space for 1 =< p =< infty and A(G) be the Fourier algebra of G. Our goal is to study, in a new abstract context, the completely bounded multipliers of A(G), which we denote M_{cb}A(G). We show that M_{cb}A(G) can be characterised as the ``invariant part'' of the space of (completely) bounded normal L^{infty}(G)-bimodule maps on B(L^2(G)), the space of bounded operator on L^2(G). In doing this we develop a function theoretic description of the normal L^{infty}(X,mu)-bimodule maps on B(L^2(X,mu)), which we denote by V^{infty}(X,μ), and nam…

A non-commutative Beurling's theorem with respect to unitarily invariant norms

In 1967, Arveson invented a non-commutative generalization of classical $H^{\infty},$ known as finite maximal subdiagonal subalgebras, for a finite von Neumann algebra $\mathcal M$ with a faithful normal tracial state $τ$. In 2008, Blecher and Labuschagne proved a version of Beurling's theorem on $H^\infty$-right invariant subspaces in a non-commutative $L^{p}(\mathcal M,τ)$ space for $1\le p\le \infty$. In the present paper, we define and study a class of norms ${\mathcal{N}}_{c}(\mathcal M, τ)$ on $\mathcal{M},$ called normalized, unitarily invariant, $\Vert \cdot \Vert_{1}$-dominating, cont…

Generalized Inner-Outer Factorization in non commutative Hardy Algebras

Let $H^{\infty}(E)$ be a non commutative Hardy algebra, associated with a $W^*$-correspondence $E$. In this paper we construct factorizations of inner-outer type of the elements of $H^{\infty}(E)$ represented via the induced representation, and of the elements of its commutant. These factorizations generalize the classical inner-outer factorization of elements of $H^\infty(\mathbb{D})$. Our results also generalize some results that were obtained by several authors in some special cases.

BMO-estimates for non-commutative vector valued Lipschitz functions

We construct Markov semi-groups $\mathcal{T}$ and associated BMO-spaces on a finite von Neumann algebra $(\mathcal{M}, τ)$ and obtain results for perturbations of commutators and non-commutative Lipschitz estimates. In particular, we prove that for any $A \in \mathcal{M}$ self-adjoint and $f: \mathbb{R} \rightarrow \mathbb{R}$ Lipschitz there is a Markov semi-group $\mathcal{T}$ such that for $x \in \mathcal{M}$, \[ \Vert [f(A), x] \Vert_{{\rm BMO}(\mathcal{M}, \mathcal{T})} \leq c_{abs} \Vert f' \Vert_\infty \Vert [A, x] \Vert_\infty. \] We obtain an analogue of this result for more general v…

III型与半有限非交换$L_p$空间的Banach非同构性

Banach non-isomorphism of type III and semifinite noncommutative $L_p$-spaces

针对具有可分预对偶的非零III型von Neumann代数M与半有限von Neumann代数N，证明M_*不同构于N_*的子空间，1<p<∞且p≠2时L_p(M)不同构于L_p(N)的补子空间，其同构类可区分两类代数。

平移不变再生核希尔伯特空间上的交换拓扑代数

Commutative topological algebras on translation-invariant reproducing kernel Hilbert spaces

研究平移不变再生核希尔伯特空间上自然关联的交换拓扑代数，通过再生核生成公共稠密域，将对角化算子与加权L²空间交集中的符号乘法等同，得到完备局部凸*-代数。

Schur 检验与非交换 $L_p$ 上正半群的估计

Schur tests and estimates for positive semigroups on non commutative $L_p$

本文利用 Schur 检验（含 von Neumann 代数新版本）将 Kreiss 正半群估计从 $L_p$ 空间推广至非交换 $L_p$ 空间，并给出尖锐例子。

Reflexivity of non commutative Hardy Algebras

Let $H^{\infty}(E)$ be a non commutative Hardy algebra, associated with a $W^*$-correspondence $E$. These algebras were introduced in 2004, ~\cite{MuS3}, by P. Muhly and B. Solel, and generalize the classical Hardy algebra of the unit disc $H^{\infty}(\mathbb{D})$. As a special case one obtains also the algebra $\mathcal{F}^{\infty}$ of Popescu, which is $H^{\infty}(\mathbb{C}^n)$ in our setting. In this paper we view the algebra $H^\infty(E)$ as acting on a Hilbert space via an induced representation $ρ(H^{\infty}(E))$, and we study the reflexivity of $ρ(H^{\infty}(E))$. This question was stu…

Operator space structures and the split property II

A characterization of the split property for an inclusion $N\subset M$ of $W^*$-factors with separable predual is established in terms of the canonical non-commutative $L^2$ embedding considered in \cite{B1,B2} $$ \F_2:a\in N\to \D_{M,\Om}^{1/4}a\Om\in L^2(M,\Om) $$ associated with an arbitrary fixed standard vector $\Om$ for $M$. This characterization follows an analogous characterization related to the canonical non-commutative $L^1$ embedding $$ \F_1:a\in N\to (\cdot\Om,J_{M,\Om}a\Om)\in L^1(M,\Om) $$ also considered in \cite{B1,B2} and studied in \cite{F}. The split property for a Quantum …

重新审视非交换极大函数的 Marcinkiewicz 定理

Revisiting the Marcinkiewicz theorem for non commutative maximal functions

本文给出了非交换极大函数与正映射的 Marcinkiewicz 插值定理的替代证明并加以细化，为 $L_p$ 鞅极大函数提供了常数损失极小的替代品，并针对非正映射通过弱化极大范数获得了插值结果。

On a generalized uniform zero-two law for positive contractions of non-commutative $L_1$-spaces and its vector-valued extension

First, Ornstein and Sucheston proved that for a given positive contraction $T:L_1\to L_1$ there exists $m\in N$ such that $\big\|T^{m+1}-T^m\|<2$ then $$ \lim_{n\to\infty}\|T^{n+1}-T^n\|=0. $$ Such a result was labeled as "zero-two" law. In the present paper, we prove a generalized uniform "zero-two" law for multi-parametric family of positive contractions of the non-commutative $L_1$-spaces. Moreover, we also establish a vector-valued analogous of the uniform "zero-two" law for positive contractions of $L_1(M,Φ)$-- the non-commutative $L_1$-spaces associated with center valued trace.

Orthogonally additive polynomials on non-commutative $L^p$-spaces

Let $\mathcal{M}$ be a von Neumann algebra with a normal semifinite faithful trace $τ$. We prove that every continuous $m$-homogeneous polynomial $P$ from $L^p(\mathcal{M},τ)$, with $0<p<\infty$, into each topological linear space $X$ with the property that $P(x+y)=P(x)+P(y)$ whenever $x$ and $y$ are mutually orthogonal positive elements of $L^p(\mathcal{M},τ)$ can be represented in the form $P(x)=Φ(x^m)$ $(x\in L^p(\mathcal{M},τ))$ for some continuous linear map $Φ\colon L^{p/m}(\mathcal{M},τ)\to X$.

关于积群中晶格张量积的非交换因子定理

Non-commutative Factor theorem for tensor products of lattices in product groups

本文研究了积群中晶格张量积的非交换因子定理，证明了中间von Neumann代数的结构特性。

Non-commutative Khintchine type inequalities associated with free groups

Let $\Free_n$ denote the free group with $n$ generators $g_1, g_2, ..., g_n$. Let $λ$ stand for the left regular representation of $\Free_n$ and let $τ$ be the standard trace associated to $λ$. Given any positive integer $d$, we study the operator space structure of the subspace $\Word_p(n,d)$ of $L_p(τ)$ generated by the family of operators $λ(g_{i_1}g_{i_2} ... g_{i_d})$ with $1 \le i_k \le n$. Moreover, our description of this operator space holds up to a constant which does not depend on $n$ or $p$, so that our result remains valid for infinitely many generators. We also consider the subsp…

Non-commutativity of the central sequence algebra for separable non-type I C$^{\ast}$-algebras

We show that if $A$ is a separable, simple and non-type I C$^{\ast}$ algebra, then for every properly infinite hyperfinite von Neumann algebra $M$ with separable predual, its Ocneanu ultrapower $M'\cap M^ω$ arises as a sub-quotient of the central sequence algebra $F(A)$ defined by the second named author. In particular, this answers affirmatively the question of the second named author (Abel Symposium '04): the central sequence C$^{\ast}$-algebra of the reduced free group C$^{\ast}$-algebra $C_{\rm{red}}^*(\mathbb{F}_2)$ is non-commutative.

Completely Order Bounded Maps on Non-Commutative $L_p$-Spaces

We define norms on $L_p(\mathcal{M}) \otimes M_n$ where $\mathcal{M}$ is a von Neumann algebra and $M_n$ is the complex $n \times n$ matrices. We show that a linear map $T: L_p(\mathcal{M}) \to L_q(\mathcal{N})$ is decomposable if $\mathcal{N}$ is an injective von Neumann algebra, the maps $T \otimes Id_{M_n}$ have a common upper bound with respect to our defined norms, and $p = \infty$ or $q = 1$. For $2p < q < \infty$ we give an example of a map $T$ with uniformly bounded maps $T \otimes Id_{M_n}$ which is not decomposable.

Conjugate operators for finite maximal subdiagonal algebras

Let $\M$ be a von Neumann algebra with a faithful normal trace $\T$, and let $H^\infty$ be a finite, maximal, subdiagonal algebra of $\M$. Fundamental theorems on conjugate functions for weak$^*$\!-Dirichlet algebras are shown to be valid for non-commutative $H^\infty$. In particular the conjugation operator is shown to be a bounded linear map from $L^p(\M, \T)$ into $L^p(\M, \T)$ for $1 < p < \infty$, and to be a continuous map from $L^1(\M,\T)$ into $L^{1, \infty}(\M,\T)$. We also obtain that if an operator $a$ is such that $|a|\log^+|a| \in L^1(\M,\T)$ then its conjugate belongs to $L^1(\M,…

非交换 $L^p$-空间上的正等距傅里叶乘子

Positive isometric Fourier multipliers on non-commutative $L^p$-spaces

研究非交换 $L^p$-空间上傅里叶乘子的正等距性质，证明其与群的连续特征函数一致的等价条件。

Factoring in Non-commutative Analytic Toeplitz Algebras

The non-commutative analytic Toeplitz algebra is the weak operator topology closed algebra generated by the left regular representation of the free semigroup on $n$ generators. The structure theory of contractions in these algebras is examined. Each is shown to have an $H^\infty$ functional calculus. The isometries defined by words are shown to factor only as the words do over the unit ball of the algebra. This turns out to be false over the full algebra. The natural identification of weakly closed left ideals with invariant subspaces of the algebra is shown to hold only for a proper subcollec…

Non-commutative Rényi Entropic Uncertainty Principles

In this paper, we calculate the norm of the string Fourier transform on subfactor planar algebras and characterize the extremizers of the inequalities for parameters $0<p,q\leq \infty$. Furthermore, we establish Rényi entropic uncertainty principles for subfactor planar algebras.

Homology of complete symbols and non-commutative geometry

We identify the periodic cyclic homology of the algebra of complete symbols on a differential groupoid $\GR$ in terms of the cohomology of $S^*(\GR)$, the cosphere bundle of $A(\GR)$, where $A(\GR)$ is the Lie algebroid of $\GR$. We also relate the Hochschild homology of this algebra with the homogeneous Poisson homology of the space $A^*(\GR) \smallsetminus 0 \cong S^*(\GR) \times (0,\infty)$, the dual of $A(\GR)$ with the zero section removed. We use then these results to compute the Hochschild and cyclic homologies of the algebras of complete symbols associated with manifolds with corners, …

非交换 $L^p$-空间中随机遍历平均的点收敛性

Pointwise Convergence for Random Ergodic Averages in Non-commutative $L^p$-spaces

本文研究非交换 $L^p$-空间中由伯努利变量确定的随机稀疏子序列的遍历平均，证明其几乎处处一致收敛到遍历投影，扩展了 Bourgain 的定理。

Non commutative Lp spaces without the completely bounded approximation property

For any 1\leq p \leq \infty different from 2, we give examples of non-commutative Lp spaces without the completely bounded approximation property. Let F be a non-archimedian local field. If p>4 or p<4/3 and r\geq 3 these examples are the non-commutative Lp-spaces of the von Neumann algebra of lattices in SL_r(F) or in SL_r(\R). For other values of p the examples are the non-commutative Lp-spaces of the von Neumann algebra of lattices in SL_r(F) for r large enough depending on p. We also prove that if r \geq 3 lattices in SL_r(F) or SL_r(\R) do not have the Approximation Property of Haagerup an…