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We study generalized polar decompositions of densely defined, closed linear operators in Hilbert spaces and provide some applications to relatively (form) bounded and relatively (form) compact perturbations of self-adjoint, normal, and…

Functional Analysis · Mathematics 2008-11-11 Fritz Gesztesy , Mark Malamud , Marius Mitrea , Serguei Naboko

We present a unitary approach to the construction of representations and intertwining operators. We apply it to the $C^*$-algebras, groups, Gabor type unitary systems and wavelets. We give an application of our method to the theory of…

Functional Analysis · Mathematics 2007-05-23 Dorin Ervin Dutkay

Using results from theory of operators on a Hilbert space, we prove approximation results for matrix-valued holomorphic functions on the unit disc and the unit bidisc. The essential tools are the theory of unitary dilation of a contraction…

Complex Variables · Mathematics 2023-06-27 Daniel Alpay , Tirthankar Bhattacharyya , Abhay Jindal , Poornendu Kumar

We present some general theorems about operator algebras that are algebras of functions on sets, including theories of local algebras, residually finite dimensional operator algebras and algebras that can be represented as the scalar…

Operator Algebras · Mathematics 2009-07-30 Meghna Mittal , Vern Paulsen

We generalize the dual notions of "expansion" and "collapse" so they can be applied to arbitrary metric spaces. We also expand the theory to allow for infinitely many such moves. Those tools are then employed to prove a variety of…

Geometric Topology · Mathematics 2023-11-07 Craig R. Guilbault , Daniel Gulbrandsen

We will give an outline of the main results in our recent AMS Memoir, and include some new results, exposition and open problems. In that memoir we developed a general dilation theory for operator valued measures acting on Banach spaces…

Functional Analysis · Mathematics 2014-11-18 Deguang Han , David R. Larson , Bei Liu , Rui Liu

A conjugation $C$ is an anti-linear isometric involution on a complex Hilbert space $\clh$, and $T\in \clb(\clh)$ is conjugate normal if $T^*T = CTT^*C$ holds for some conjugation (C). In this paper, we provide a factorization and range…

Functional Analysis · Mathematics 2024-03-05 Sudip Ranjan Bhuia

In the present paper, we propose to give an extension to the context of Dunkl theory of the notion of translation and in connection with this a corresponding extension of Taylor's formula. More precisely, we prove some properties and…

Functional Analysis · Mathematics 2017-04-25 Chokri Abdelkefi , Safa Chabchoub

A classical result of Sz.-Nagy asserts that a Hilbert space contraction operator $T$ can be dilated to a unitary $\cU$. A more general multivariable setting for these ideas is the setup where (i) the unit disk is replaced by a domain…

Functional Analysis · Mathematics 2022-07-08 Joseph A. Ball , Haripada Sau

We establish a Wold-type decomposition for isometric and isometric Nica-covariant representations of the odometer semigroup. These generalize the Wold-type decomposition for commuting pairs of isometries due to Popovici and for pairs of…

Operator Algebras · Mathematics 2021-08-10 Boyu Li

Fix 1<R. The dilation theory for the quantum annulus, consisting of those invertible Hilbert space operators T such that the norm of T and its inverse are both at most R is determined. The proof technique involves a geometric approach to…

Functional Analysis · Mathematics 2023-01-09 Scott McCullough , James E. Pascoe

Given a bounded operator $Q$ on a Hilbert space $\mathcal{H}$, a pair of bounded operators $(T_1, T_2)$ on $\mathcal{H}$ is said to be $Q$-commuting if one of the following holds: \[ T_1T_2=QT_2T_1 \text{ or }T_1T_2=T_2QT_1 \text{ or…

Functional Analysis · Mathematics 2022-10-20 Sibaprasad Barik , Bappa Bisai

We provide an explicit normal distinguished boundary dilation to a pair of commuting operators $(S,P)$ having the closed symmetrized bidisc $\Gamma$ as a spectral set. This is called Sz.-Nagy dilation of $(S,P)$. The operator pair that…

Functional Analysis · Mathematics 2015-07-29 Sourav Pal

An analysis is given of $*$-representations of rank 2 single vertex graphs. We develop dilation theory for the non-selfadjoint algebras $\A_\theta$ and $\A_u$ which are associated with the commutation relation permutation $\theta$ of a 2…

Operator Algebras · Mathematics 2007-06-01 Kenneth R. Davidson , Stephen C. Power , Dilian Yang

We establish a finite-dimensional version of the Arveson-Stinespring dilation theorem for unital completely positive maps on operator systems. This result can be seen as a general principle to deduce finite-dimensional dilation theorems…

Functional Analysis · Mathematics 2022-04-25 Michael Hartz , Martino Lupini

Let $\mathcal{M}$ be an indefinite inner product module over a *-ring of characteristic 2. We show that every self-adjoint operator on $\mathcal{M}$ admits Halmos, Egervary and Sz.-Nagy dilations.

Rings and Algebras · Mathematics 2022-10-12 K. Mahesh Krishna

We still extend the large class of Dirac operators decribing massless fermions on the lattice found recently, only requiring that such operators decompose into Weyl operators. After deriving general relations and constructions of operators,…

High Energy Physics - Lattice · Physics 2014-11-17 Werner Kerler

The main aims of this article are to characterize a class of operators associated with the symmetrized polydisc that admit rational dilations on the minimal space and to show an interplay between rational dilation and distinguished…

Functional Analysis · Mathematics 2022-04-18 Sourav Pal

The usual Laurent expansion of the analytic tensors on the complex plane is generalized to any closed and orientable Riemann surface represented as an affine algebraic curve. As an application, the operator formalism for the $b-c$ systems…

High Energy Physics - Theory · Physics 2015-06-26 F. Ferrari , J. Sobczyk

Self-adjoint Dirac systems and subclasses of canonical systems, which generalize Dirac systems are studied. Explicit and global solutions of direct and inverse problems are obtained. A local Borg-Marchenko-type theorem, integral…

Classical Analysis and ODEs · Mathematics 2012-11-29 B. Fritzsche , B. Kirstein , A. L. Sakhnovich