A noncommutative version of the Banach-Stone Theorem

Ergodic theorems in fully symmetric spaces of $τ-$measurable operators

In [11], employing the technique of noncommutative interpolation, a maximal ergodic theorem in noncommutative Lp-spaces, 1 < p < infinity, was established and, among other things, corresponding maximal ergodic inequalities and individual ergodic theorems were derived. In this article, we derive maximal ergodic inequalities in noncommutative Lp-spaces directly from [25] and apply them to prove corresponding individual and Besicovitch weighted ergodic theorems. Then we extend these results to noncommutative fully symmetric Banach spaces with Fatou property and non-trivial Boyd indices, in partic…

Majorization, Interpolation and noncommutative Khintchine inequalities

Let $0<p<q\leq\infty$ and $α\in (0,\infty]$. We give a characterization of quasi-Banach interpolation spaces for the couple $(L_p(0,α),L_q(0,α))$ in terms of two monotonicity properties, extending known results which mainly dealt with Banach spaces. This enables us to recover recent results of Cwikel and Nilsson on sequence spaces and to solve a conjecture of Levitina, Sukochev and Zanin in the setting of function spaces. We apply the results obtained to characterize symmetric spaces in which the standard forms of the noncommutative Khintchine inequalities hold.

Noncommutative Pierce Duality between Steinberg Rings and Ample Ringoid Bundles

Classic work of Pierce and Dauns-Hofmann shows that biregular rings are dual to simple ring bundles over Stone spaces. We extend this duality to Steinberg rings, a purely algebraic generalisation of Steinberg algebras, and ringoid bundles over ample groupoids. We base this largely on an even more general extension of Lawson's noncommutative Stone duality, specifically between Steinberg semigroups, a generalisation of Boolean inverse semigroups, and category bundles over ample groupoids.

通过非交换几何棱镜观察经典调和分析

Classical harmonic analysis viewed through the prism of noncommutative geometry

本文通过非交换几何框架，将经典调和分析与L^p空间分析结合，提出新的K-理论群和索引定理，揭示Hilbert变换和Riesz变换的作用。

Grothendieck's inequality in the noncommutative Schwartz space

In the spirit of Grothendieck's famous inequality from the theory of Banach spaces, we study a sequence of inequalities for the noncommutative Schwartz space, a Fréchet algebra of smooth operators. These hold in non-optimal form by a simple nuclearity argument. We obtain optimal versions and reformulate the inequalities in several different ways.

Noncommutative Lp structure encodes exactly Jordan structure

We prove that for all 1 \le p \le \infty, p not 2, the Lp spaces associated to two von Neumann algebras M,N are isometrically isomorphic if and only if M and N are Jordan *-isomorphic. This follows from a noncommutative Lp Banach-Stone theorem: a specific decomposition for surjective isometries of noncommutative Lp spaces.

Banach 空间上压缩投影的模理论及其在非交换 $\mathrm{L}^p$-空间中的应用

A modular theory of contractive projections on Banach spaces with applications to noncommutative $\mathrm{L}^p$-spaces

本文提出基于 Levi 形式的模理论，刻画 Banach 空间压缩投影，并应用于非交换 L^p 空间，证明 2-压缩投影等价于完全压缩，且值域具有三元结构。

On pointwise products of symmetric quasi Banach spaces and applications

Let $E_1,\;E_2$ be symmetric quasi Banach function spaces on $(0,α)\;(0<α\le\8)$. We study some properties of several constructions (the products $E_1(\M)\odot E_2(\M)$, the Calder$\rm\acute{o}$n spaces $E_1(\M)^θE_2(\M)^{1-θ}$, the complex interpolation spaces $(E_1(\M),E_2(\M))_θ$, the real interpolation method $(E_1(\M),E_2(\M))_{θ,p}$) in the context of noncommutative symmetric quasi Banach spaces. Under some natural assumptions, we prove $$ (E_1(\M), E_2(\M))_θ=E_1(\M)^θE_2(\M)^{1-θ}=E_1^{(\frac{1}θ)}(\M)\odot E_2^{(\frac{1}{1-θ})}(\M)\;(0<θ<1). $$ As application, we extend these result t…

Inverse-Closed Subalgebras of Noncommutative Tori

We give a systematic construction of inverse-closed (Banach) subalgebras in general higher-dimensional non-commutative tori

On noncommutative weighted local ergodic theorems

In the present paper we consider a von Neumann algebra M with a faithful normal semi-finite trace $\t$, and $\{α_ t\} $ a strongly continuous extension to $L^p(M,\t)$ of a semigroup of absolute contractions on $L^1 (M,τ)$. By means of a non-commutative Banach Principle we prove for a Besicovitch function b and $x\in L^p(M,\t)$, the averages \frac{1}{T}\int_0^Tb(t)\a_t(x)dt converge bilateral almost uniform in $L^p(M,\t)$ as $T\to 0$.

P. Jones'Interpolation theorem for noncommutative martingale Hardy spaces

Let $\mathcal{M}$ be a semifinite von Nemann algebra equipped with an increasing filtration $(\mathcal{M}_n)_{n\geq 1}$ of (semifinite) von Neumann subalgebras of $\M$. For $0<p \leq\infty$, let $\h_p^c(\mathcal{M})$ denote the noncommutative column conditioned martingale Hardy space associated with the filtration $(\mathcal{M}_n)_{n\geq 1}$ and the index $p$. We prove that for $0<p<\infty$, the compatible couple $\big(\h_p^c(\mathcal{M}), \h_\infty^c(\mathcal{M})\big)$ is $K$-closed in the couple $\big(L_p(\mathcal{N}), L_\infty(\mathcal{N}) \big)$ for an appropriate amplified semifinite von …

非交换 $L_p$-空间到非交换对称空间的等距嵌入

Isometric embeddings of noncommutative $L_p$-spaces into noncommutative symmetric spaces

本文建立了非交换版本的Johnson--Maurey--Schechtman--Tzafriri定理，证明任意$L_p$空间可等距嵌入到满足特定条件的非交换对称空间，并解决了2006年的两个公开问题。

酉不变理想球面之间的均匀同胚

Uniform homeomorphisms between spheres of unitarily invariant ideals

本文证明非交换版本的Odell-Schlumprecht定理，通过两类广义Mazur映射（基于p-凸化和量子相对熵最小化）建立酉不变理想球面与Hilbert空间球面间的均匀同胚，提供满足性质(H)的新例子。

Approximation properties for noncommutative $L^p$-spaces of high rank lattices and nonembeddability of expanders

This article contains two rigidity type results for $\mathrm{SL}(n,\mathbb{Z})$ for large $n$ that share the same proof. Firstly, we prove that for every $p \in [1,\infty]$ different from $2$, the noncommutative $L^p$-space associated with $\mathrm{SL}(n,\mathbb{Z})$ does not have the completely bounded approximation property for sufficiently large $n$ depending on $p$. The second result concerns the coarse embeddability of expander families constructed from $\mathrm{SL}(n,\mathbb{Z})$. Let $X$ be a Banach space and suppose that there exist $β< \frac{1}{2}$ and $C>0$ such that the Banach-Mazur…

非交换极大遍历定理：算子值权重的调制$(C,\alpha)$平均

Noncommutative Maximal Ergodic Theorems for Modulated $(C,α)$-Averages with Operator-Valued Weights

本文在半有限冯·诺依曼代数上，通过引入$p$-凸Orlicz函数条件，建立了带算子值权重的调制$(C,\alpha)$平均的极大遍历定理与逐点收敛，并推广了Rota定理。

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 …

A Ribe theorem for noncommutative L$_1$-spaces and Lipschitz free operator spaces

These notes have the intent to introduce the study of the nonlinear aspects of operator space theory. We investigate some results on the nonlinear theory of Banach spaces which remain valid in the noncommutative case. In particular, we show that Ribe's theorem has a complete analog to preduals of von Neumann algebras and introduce the concept of the Lipschitz free operator space of an operator space. We use those to prove results about injective von Neumann algebras, Pisier's operator space OH, and the existence of complete linear isometric embeddings between operator spaces.

Von Neumann algebra conditional expectations with applications to generalized representing measures for noncommutative function algebras

We establish several deep existence criteria for conditional expectations on von Neumann algebras, and then apply this theory to develop a noncommutative theory of representing measures of characters of a function algebra. Our main cycle of results describes what may be understood as a `noncommutative Hoffman-Rossi theorem' giving the existence of weak* continuous `noncommutative representing measures' for so-called D-characters. These results may also be viewed as `module' Hahn-Banach extension theorems for weak* continuous `characters' into possibly noninjective von Neumann algebras. In clos…

Noncommutative Wiener-Wintner type ergodic theorems

In this article, we obtain a version of the noncommutative Banach Principle suitable to prove Wiener-Wintner type results for weights in W1-space. This is used to obtain noncommutative Wiener-Wintner type ergodic theorems for various types of weights for certain types of positive Dunford-Schwartz operators. We also study the b.a.u. (a.u.) convergence of some subsequential averages and moving averages of such operators

非交换正则性结构

Noncommutative Regularity Structures

本文推广正则性结构理论至局部$m$-凸拓扑代数，涵盖局部$C^*$-代数及$q$-高斯过程，并引入新范数解决非交换重整化估计挑战。

Interpolation between noncommutative martingale Hardy and BMO spaces: the case $0<p<1$

Let $\mathcal{M}$ be a semifinite von Nemann algebra equipped with an increasing filtration $(\mathcal{M}_n)_{n\geq 1}$ of (semifinite) von Neumann subalgebras of $\mathcal{M}$. For $0<p <\infty$, let $\mathsf{h}_p^c(\mathcal{M})$ denote the noncommutative column conditioned martingale Hardy space and $\bmo^c(\M)$ denote the column \lq\lq little\rq\rq \ martingale BMO space associated with the filtration $(\mathcal{M}_n)_{n\geq 1}$. We prove the following real interpolation identity: if $0<p <\infty$ and $0<θ<1$, then for $1/r=(1-θ)/p$, \[ \big(\mathsf{h}_p^c(\mathcal{M}), \bmo^c(\mathcal{M})\…

C*-Segal algebras with order unit

We introduce the notion of a (noncommutative) C*-Segal algebra as a Banach algebra which is a dense ideal in a C*-algebra. Several basic properties are investigated and, with the aid of the theory of multiplier modules, the structure of C*-Segal algebras with order unit is determined.

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 …

A Beurling-Chen-Hadwin-Shen Theorem for Noncommutative Hardy Spaces Associated with Semifinite von Neumann Algebras with Unitarily Invariant Norms

We introduce a class of unitarily invariant, locally $\|\cdot\|_1$-dominating, mutually continuous norms with repect to $τ$ on a von Neumann algebra $\mathcal{M}$ with a faithful, normal, semifinite tracial weight $τ$. We prove a Beurling-Chen-Hadwin-Shen theorem for $H^\infty$-invariant spaces of $L^α(\mathcal{M},τ)$, where $α$ is a unitarily invariant, locally $\|\cdot\|_1$-dominating, mutually continuous norm with respect to $τ$, and $H^\infty$ is an extension of Arveson's noncommutative Hardy space. We use our main result to characterize the $H^\infty$-invariant subspaces of a noncommutati…

A classification for 2-isometries of noncommutative Lp-spaces

In this paper we extend previous results of Banach, Lamperti and Yeadon on isometries of Lp-spaces to the non-tracial case first introduced by Haagerup. Specifically, we use operator space techniques and an extrapolation argument to prove that every 2-isometry T : Lp(M) to Lp(N) between arbitrary noncommutative Lp-spaces can always be written in the form T(phi^{1/p}) = w (phi circ pi^{-1} circ E)^{1/p}, for phi in M_*^+. Here pi is a normal *-isomorphism from M onto the von Neumann subalgebra pi(M) of N, w is a partial isometry in N, and E is a normal conditional expectation from N onto pi(M).…

非交换逼近：逆封闭子代数与矩阵的非对角衰减

Noncommutative Approximation: Inverse-Closed Subalgebras and Off-Diagonal Decay of Matrices

本文受逼近论经典原理启发，研究了Banach代数或算子代数中逆封闭子代数的两种系统构造，并将其应用于具有非对角衰减的无限矩阵代数，得到了矩阵求逆下保持的新的非对角衰减条件。

Derived Analytic Geometry for Z-Valued Functions. Part I -- Topological Properties

We study the Banach algebras ${\rm C}(X, R)$ of continuous functions from a compact Hausdorff topological space $X$ to a Banach ring $R$ whose topology is discrete. We prove that the Berkovich spectrum of ${\rm C}(X, R)$ is homeomorphic to $ζ(X) \times {\mathcal M}(R)$, where $ζ(X)$ is the Banaschewski compactification of $X$ and ${\mathcal M}(R)$ is the Berkovich spectrum of $R$. We study how the topology of the spectrum of ${\rm C}(X, R)$ is related to the notion of homotopy Zariski open embedding used in derived geometry. We find that the topology of $ζ(X)$ can be easily reconstructed from …

The Shilov boundary of an operator space - and the characterization theorems

We study operator spaces, operator algebras, and operator modules, from the point of view of the `noncommutative Shilov boundary'. In this attempt to utilize some `noncommutative Choquet theory', we find that Hilbert C$^*-$modules and their properties, which we studied earlier in the operator space framework, replace certain topological tools. We introduce certain multiplier operator algebras and C$^*-$algebras of an operator space, which generalize the algebras of adjointable operators on a C$^*-$module, and the `imprimitivity C$^*-$algebra'. It also generalizes a classical Banach space notio…

Lamperti 运算符、扩张理论及其在非交换遍历理论中的应用

Lamperti Operators, Dilation Theory, and Applications in Noncommutative Ergodic Theory

本文提出非交换环境下定量遍历定理的新框架，结合Lamperti运算符和扩张理论，扩展了经典定理并应用于非交换 $L_p$-空间。

The disappearance of causality at small scale in almost-commutative manifolds

This paper continues the investigations of noncommutative ordered spaces put forward by one of the authors. These metaphoric spaces are defined dually by so-called \emph{isocones} which generalize to the noncommutative setting the convex cones of order-preserving functions. In this paper we will consider the case of isocones inside almost-commutative algebras of the form ${\cal C}(M)\otimes A_f$, with $M$ a compact metrizable space. We will give a family of isocones in such an algebra with the property that every possible isocone is contained in exactly one member of the family. We conjecture …

曲率、Dolbeault-Dirac算子以及紧Kähler流形上的$\mathrm{L}^p$-指标定理

Curvature, Dolbeault-Dirac operators, and an $\mathrm{L}^p$-index theorem on compact Kähler manifolds

本文在紧Kähler流形上建立了Dolbeault-Dirac算子的$\mathrm{L}^p$-Banach非交换几何框架，证明了其闭实现是双扇形的且具有有界$\mathrm{H}^\infty$泛函演算，并得到$\mathrm{L}^p$-Hodge分解和Fredholm算子的指标等于全纯Euler示性数。