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A subset P of N x N is called Schur bounded if every infinite matrix with bounded entries which is zero off of P yields a bounded Schur multiplier on B(H). Such sets are characterized as being the union of a subset with at most k entries in…

Operator Algebras · Mathematics 2007-05-23 Kenneth R. Davidson , Allan P. Donsig

Let $G$ be a discrete group. Let $\lambda : G \to B(\ell_2(G),\ell_2(G))$ be the left regular representation. A function $\ph : G \to \comp$ is called a completely bounded multiplier (= Herz-Schur multiplier) if the transformation defined…

Functional Analysis · Mathematics 2016-09-06 Gilles Pisier

In this paper, we will consider matrices with entries in the space of operators $\mathcal{B}(H)$, where $H$ is a separable Hilbert space, and consider the class of (left or right) Schur multipliers that can be approached in the multiplier…

Functional Analysis · Mathematics 2018-10-21 O. Blasco , I. García-Bayona

Let $G$ be an infinite locally compact abelian group. If $X$ is Banach space, we show that if every bounded Fourier multiplier $T$ on $L^2(G)$ has the property that $T\ot Id_X$ is bounded on $L^2(G,X)$ then the Banach space $X$ is…

Functional Analysis · Mathematics 2012-04-03 Cédric Arhancet

Schur multipliers are basic linear maps on matrix algebras. Their close albeit still intriguing connection with Fourier multipliers establishes a powerful bridge between harmonic analysis and operator algebras. In this paper, we survey…

Operator Algebras · Mathematics 2025-10-21 Javier Parcet

We study the space of functions $\phi\colon \NN\to \CC$ such that there is a Hilbert space $H$, a power bounded operator $T$ in $B(H)$ and vectors $\xi,\eta$ in $H$ such that $$\phi(n) = < T^n\xi,\eta>.$$ This implies that the matrix…

Functional Analysis · Mathematics 2007-05-23 Gilles Pisier

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…

Functional Analysis · Mathematics 2023-01-13 Erik Christensen

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…

Functional Analysis · Mathematics 2007-05-23 Nico Spronk

Consider a completely bounded Fourier multiplier phi of a locally compact group G, and take 1 <= p <= infinity. One can associate to phi a Schur multiplier on the Schatten classes S_p(L^2 G), as well as a Fourier multiplier on Lp(LG), the…

Functional Analysis · Mathematics 2017-10-05 Martijn Caspers , Mikael de la Salle

We introduce partially defined Schur multipliers and obtain necessary and sufficient conditions for the existence of extensions to fully defined positive Schur multipliers, in terms of operator systems canonically associated with their…

Operator Algebras · Mathematics 2018-08-29 Rupert H. Levene , Ying-Fen Lin , Ivan G. Todorov

We obtain descriptions of central operator-valued Schur and Herz-Schur multipliers, akin to a classical characterisation due to Grothendieck, that reveals a close link between central (linear) multipliers and bilinear multipliers into the…

Functional Analysis · Mathematics 2021-01-05 Andrew McKee , Reyhaneh Pourshahami , Ivan G. Todorov , Lyudmila Turowska

We define the Schur multipliers of a separable von Neumann algebra M with Cartan masa A, generalising the classical Schur multipliers of $B(\ell^2)$. We characterise these as the normal A-bimodule maps on M. If M contains a direct summand…

Operator Algebras · Mathematics 2018-08-22 Rupert H. Levene , Nico Spronk , Ivan G. Todorov , Lyudmila Turowska

We study in this paper properties of Schur multipliers of Schatten von Neumann classes $\boldsymbol{S}_p$. We prove that for $p\le1$, Schur multipliers of $\boldsymbol{S}_p$ are necessarily completely bounded. We also introduce for $p\le1$…

Functional Analysis · Mathematics 2019-10-21 Aleksei Aleksandrov , Vladimir Peller

A map between operator spaces is called completely coarse if the sequence of its amplifications is equi-coarse. We prove that all completely coarse maps must be $\mathbb R$-linear. On the opposite direction of this result, we introduce a…

Operator Algebras · Mathematics 2020-06-02 Bruno M. Braga , Javier Alejandro Chávez-Domínguez

We introduce a noncommutative analogue of the Fig\'a-Talamanca-Herz algebra $A_p(G)$ on the natural predual of the operator space $\frak{M}_{p,cb}$ of completely bounded Schur multipliers on Schatten space $S_p$. We determine the isometric…

Operator Algebras · Mathematics 2011-09-26 Cédric Arhancet

A Schur multiplier is a linear map on matrices which acts on its entries by multiplication with some function, called the symbol. We consider idempotent Schur multipliers, whose symbols are indicator functions of smooth Euclidean domains.…

Functional Analysis · Mathematics 2025-04-02 Javier Parcet , Mikael de la Salle , Eduardo Tablate

It is well-known that if T is a D_m-D_n bimodule map on the m by n complex matrices, then T is a Schur multiplier and $\|T\|_{cb}=\|T\|$. If n=2 and T is merely assumed to be a right D_2-module map, then we show that $\|T\|_{cb}=\|T\|$.…

Functional Analysis · Mathematics 2016-05-27 Rupert H. Levene , Richard M. Timoney

We prove several versions of Grothendieck's Theorem for completely bounded linear maps $T\colon E \to F^*$, when E and F are operator spaces. We prove that if E,F are $C^*$-algebras, of which at least one is exact, then every completely…

Operator Algebras · Mathematics 2015-06-26 Gilles Pisier , Dimitri Shlyakhtenko

For the Fourier Algebra of SL(2,R) any bounded multiplier is completely bounded.

Functional Analysis · Mathematics 2019-12-03 Viktor Losert

In this paper, we characterize the multiple operator integrals mappings which are bounded on the Haagerup tensor product of spaces of compact operators. We show that such maps are automatically completely bounded and prove that this is…

Functional Analysis · Mathematics 2019-08-22 Clément Coine
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