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In this work, we consider the problem of learning nonlinear operators that correspond to discrete-time nonlinear dynamical systems with inputs. Given an initial state and a finite input trajectory, such operators yield a finite output…

Optimization and Control · Mathematics 2024-12-25 Mircea Lazar

This is the third part in a series of papers developing a tensor product theory for modules for a vertex operator algebra. The goal of this theory is to construct a ``vertex tensor category'' structure on the category of modules for a…

q-alg · Mathematics 2008-02-03 Yi-Zhi Huang , James Lepowsky

This paper considers universal Hilbert space operators in the sense of Rota, and gives criteria for universality of semigroups in the context of uniformly continuous semigroups and contraction semigroups. Specific examples are given.…

Functional Analysis · Mathematics 2018-05-09 B. Célariès , I. Chalendar , J. R. Partington

A regular generalized sampling theory in some structured T-invariant subspaces of a Hilbert space H, where T denotes a bounded invertible operator in H, is established in this paper. This is done by walking through the most important cases…

Functional Analysis · Mathematics 2018-04-10 Antonio G. García , María J. Muñoz-Bouzo , Gerardo Pérez-Villalón

Given a separable unital C*algebra $C$, let $E_n$ denote the Hilbert module equal to the completion of the Schwartz space of rapidly decreasing smooth functions from $R^n$ to $C$ equipped with the $C$-valued inner product given by…

Operator Algebras · Mathematics 2007-05-23 Severino T. Melo , Marcela I. Merklen

In this paper, we extend the definition of hyperinner product defined on weak hypervector spaces with a hyperoperation scalar product to weak hypervector spaces with the hyperoperations sum and scalar products.

Functional Analysis · Mathematics 2016-10-04 Ali Taghavi , Roja Hosseinzadeh

We introduce a notion of $(S+N)$-triangular operators in the Hilbert space using some basic ideas from triangular representation theory. Our notion generalizes the well-known notion of the spectral operators so that many properties of the…

Spectral Theory · Mathematics 2016-11-03 Lev Sakhnovich

The concept of a relatively weakly injective pair of operator systems is introduced and studied in this paper, motivated by relative weak injectivity in the C*-algebra category. E. Kirchberg \cite{Kr} proved that the C*-algebra…

Operator Algebras · Mathematics 2014-05-13 Angshuman Bhattacharya

We study several classes of indecomposable representations of quivers on infinite-dimensional Hilbert spaces and their relation. Many examples are constructed using strongly irreducible operators. Some problems in operator theory are…

Operator Algebras · Mathematics 2013-03-12 Masatoshi Enomoto , Yasuo Watatani

We present several operator and norm inequalities for Hilbert space operators. In particular, we prove that if $A_{1},A_{2},...,A_{n}\in {\mathbb B}({\mathscr H})$, then…

Functional Analysis · Mathematics 2011-01-21 M. Erfanian Omidvar , M. S. Moslehian , A. Niknam

We generalize the tensor product theory for modules for a vertex operator algebra previously developed in a series of papers by the first two authors to suitable module categories for a ''conformal vertex algebra'' or even more generally,…

Quantum Algebra · Mathematics 2008-07-07 Yi-Zhi Huang , James Lepowsky , Lin Zhang

Jordan operator algebras are norm-closed spaces of operators on a Hilbert space which are closed under the Jordan product. The discovery of the present paper is that there exists a huge and tractable theory of possibly nonselfadjoint Jordan…

Operator Algebras · Mathematics 2017-12-20 David P. Blecher , Zhenhua Wang

We shall say that a densely defined closed operator $T$ on a Hilbert space is balanced if $\cD(T)=\cD(T^*)$. Balanced operators are described in terms of their phase operators abnd their moduli. Examples of balanced operators are developed.…

Functional Analysis · Mathematics 2021-03-15 Konrad Schmüdgen

We consider a tensor product of two spaces of holomorphic functions on a Hermitian symmetric space of tube type. Then generically this is decomposed into a direct sum of irreducible subrepresentations. In this manuscript, we construct the…

Representation Theory · Mathematics 2026-03-24 Ryosuke Nakahama

In this paper, we characterize hypercyclic generalized bilateral weighted shift operators on the standard Hilbert module over the C*-algebra of compact operators on the separable Hilbert space. Moreover, we give necessary and sufficient…

Operator Algebras · Mathematics 2024-01-17 Stefan Ivkovic

We study crossed products of arbitrary operator algebras by locally compact groups of completely isometric automorphisms. We develop an abstract theory that allows for generalizations of many of the fundamental results from the selfadjoint…

Operator Algebras · Mathematics 2018-11-21 Elias Katsoulis , Christopher Ramsey

This paper delves into several characterizations of $A$-approximate point spectrum of A-bounded operators acting on a complex semi-Hilbertian space $H$ and also investigates properties of the $A$-approximate point spectrum for the tensor…

Functional Analysis · Mathematics 2024-03-11 Arup Majumdar , P. Sam Johnson

Let $H$ be a reflexive, dense, separable, infinite dimensional complex Hilbert space and let $B(H)$ be the algebra of all bounded linear operators on $H$. In this paper, we carry out characterizations of norm-attainable operators in normed…

Functional Analysis · Mathematics 2020-04-14 Benard Okelo

Some preliminaries and basic facts regarding unbounded Wiener-Hopf operators (WH) are provided. WH with rational symbols are studied in detail showing that they are densely defined closed and have finite dimensional kernels and deficiency…

Functional Analysis · Mathematics 2021-05-18 Domenico P. L. Castrigiano

In this paper we introduce a generalization of Hilbert C-modules which are pre- Finsler module namely C-semi-inner product spaces. Some properties and results of such spaces are investigated, specially the orthogonality in these spaces will…

Functional Analysis · Mathematics 2013-09-06 Saeedeh Shamsi Gamchi , Mohammad Janfada , Asadollah Niknam