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Paul Halmos' work in dilation theory began with a question and its answer: Which operators on a Hilbert space can be extended to normal operators on a larger Hilbert space? The answer is interesting and subtle. The idea of representing…

Operator Algebras · Mathematics 2009-02-24 William Arveson

We develop elements of a general dilation theory for operator-valued measures and bounded linear maps between operator algebras that are not necessarily completely-bounded. We prove our main results by extending and generalizing some known…

Operator Algebras · Mathematics 2012-07-23 Deguang Han , David R. Larson , Bei Liu , Rui Liu

Given a row contraction of operators on Hilbert space and a family of projections on the space which stabilize the operators, we show there is a unique minimal joint dilation to a row contraction of partial isometries which satisfy natural…

Functional Analysis · Mathematics 2007-05-23 Michael T. Jury , David W. Kribs

Dilation theory is a paradigm for studying operators by way of exhibiting an operator as a compression of another operator which is in some sense well behaved. For example, every contraction can be dilated to (i.e., is a compression of) a…

Operator Algebras · Mathematics 2020-02-18 Orr Shalit

Sz.-Nagy and Foias proved that each $C_{\cdot0}$-contraction has a dilation to a Hardy shift and thus established an elegant analytic functional model for contractions of class $C_{\cdot0}$. This has motivated lots of further works on model…

Functional Analysis · Mathematics 2020-04-21 Hui Dan , Kunyu Guo

We introduce the notion of $Q$-commuting operators which is a generalization of commuting operators. We prove a generalized version of commutant lifting theorem and Ando's dilation theorem in the context of $Q$-commuting operators.

Functional Analysis · Mathematics 2019-10-31 Nirupama Mallick , K. Sumesh

We obtain dilation results which simultaneously generalize Sz.-Nagy dilation theorem for contractions, Ando's dilation theorem for commuting contractions, Sz.-Nagy--Foias commutant lifting theorem, and Schur's representation for the unit…

Functional Analysis · Mathematics 2017-01-12 Gelu Popescu

The explicit constructions of minimal isometric, and minimal unitary dilations of an arbitrary linear pencil of operators $T(\lambda)=T_0+\lambda T_1$ consisting of contractions on a separable Hilbert space for $|\lambda |=1$, which…

Functional Analysis · Mathematics 2007-05-23 Dmitriy S. Kalyuzhniy

In this note, we develop a parallel theory of the classical Sz.-Nagy--Foias dilation and model theory for a single contraction operator in the setting of pairs of \em{{$q$-commuting}} contraction operators for a unimodular complex number…

Functional Analysis · Mathematics 2025-11-19 Sourav Ghosh

We develop a dilation theory for row contractions subject to constraints determined by sets of noncommutative polynomials. Under natural conditions on the constraints, we have uniqueness for the minimal dilation. A characteristic function…

Operator Algebras · Mathematics 2007-05-23 Gelu Popescu

We present a completely new structure theoretic approach to the dilation theory of linear operators. Our main result is the following theorem: if $X$ is a super-reflexive Banach space and $T$ is contained in the weakly closed convex hull of…

Functional Analysis · Mathematics 2018-10-10 Stephan Fackler , Jochen Glück

The principal theorem of Sz.-Nagy on dilation of a positive definite Hilbert space operator valued function has played a central role in the development of the non-self-adjoint operator theory. In this paper we introduce the positive…

Functional Analysis · Mathematics 2015-04-30 Dumitru Gaşpar , Păstorel Gaşpar , Nicolae Lupa

This expository essay discusses a finite dimensional approach to dilation theory. How much of dilation theory can be worked out within the realm of linear algebra? It turns out that some interesting and simple results can be obtained. These…

Functional Analysis · Mathematics 2014-12-23 Eliahu Levy , Orr Shalit

We introduce a notion called `maximal commuting piece' for tuples of Hilbert space operators. Given a commuting tuple of operators forming a row contraction there are two commonly used dilations in multivariable operator theory. Firstly…

Operator Algebras · Mathematics 2014-05-16 B. V. Rajarama Bhat , Tirthankar Bhattacharyya , Santanu Dey

We obtain intertwining dilation theorems for noncommutative regular domains D_f and noncommutative varieties V_J of n-tuples of operators, which generalize Sarason and Sz.-Nagy--Foias commutant lifting theorem for commuting contractions. We…

Functional Analysis · Mathematics 2017-01-04 Gelu Popescu

Based on explicit computations, various concepts of discrete time scattering theory are reviewed, discussed, and illustrated. The dynamics are taking place on a discrete half-space. All operators are represented graphically. The expressions…

Mathematical Physics · Physics 2024-10-07 Rafi Rizqy Firdaus , Serge Richard

This manuscript is an effort to extend the Sz.-Nagy--Foias dilation and model theory for a single contraction to the case of commuting pair of contractions. Fundamental to the Sz.-Nagy--Foias model theory is the functional model for the…

Functional Analysis · Mathematics 2023-08-16 Joseph A. Ball , Haripada Sau

Let $H_m(\mathbb B)$ be the analytic functional Hilbert space on the unit ball $\mathbb B \subset \mathbb C^n$ with reproducing kernel $K_m(z,w) = (1 - \langle z,w \rangle)^{-m}$. Using algebraic operator identities we characterize those…

Functional Analysis · Mathematics 2018-01-24 Jörg Eschmeier , Sebastian Langendörfer

Higher-rank versions of Wold decomposition are shown to hold for doubly commuting isometric representations of product systems of C*-correspondences over N^k, generalising the classical result for a doubly commuting pair of isometries due…

Operator Algebras · Mathematics 2007-05-23 Adam Skalski , Joachim Zacharias

This note introduces a special class of tuples of bounded operators on a Hilbert space. It is called the Agler Young class. Major results about this class include a Wold decomposition and a dilation theorem. The structure of the dilation is…

Functional Analysis · Mathematics 2018-09-25 Tirthankar Bhattacharyya , Subrata Shyam Roy , Tapesh Yadav
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