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We review how some multianalytic inner functions of the Beurling type theorem are associated to row contractions following works of G.Popescu. Motivated by a result on weak Markov dilations, we define a notion of characteristic function for…

Operator Algebras · Mathematics 2009-03-30 Santanu Dey

The characteristic function of row contractions and liftings of row contractions are complete invariants up to unitary equivalence for row contractions and liftings of row contractions, respectively. We provide alternate proofs for these…

Functional Analysis · Mathematics 2023-02-01 Neeru Bala , Santanu Dey , Reshmi M. N

We introduce characteristic functions for certain contractive liftings of row contractions. These are multi-analytic operators which classify the liftings up to unitary equivalence and provide a kind of functional model. The most important…

Operator Algebras · Mathematics 2007-07-11 Santanu Dey , Rolf Gohm

The characteristic function has been an important tool for studying completely non unitary contractions on Hilbert spaces. In this note, we consider completely non-coisometric contractive tuples of commuting operators on a Hilbert space…

Operator Algebras · Mathematics 2007-05-23 T. Bhattacharyya , J. Eschmeier , J. Sarkar

Characteristic functions of linear operators are analytic functions that serve as complete unitary invariants. Such functions, as long as they are built in a natural and canonical manner, provide representations of inner functions on a…

Functional Analysis · Mathematics 2025-02-04 Ramlal Debnath , Deepak K. Pradhan , Jaydeb Sarkar

We introduce the notion of characteristic functions for commuting tuples of hypercontractions on Hilbert spaces, as a generalization of the notion of Sz.-Nagy and Foias characteristic functions of contractions. We present an explicit method…

Functional Analysis · Mathematics 2019-05-22 Monojit Bhattacharjee , B. Krishna Das , Jaydeb Sarkar

A characteristic function is a special operator-valued analytic function defined on the open unit ball of $\mathbb{C}^n$ associated with an $n$-tuple of commuting row contraction on some Hilbert space. In this paper, we continue our study…

Functional Analysis · Mathematics 2020-08-06 Monojit Bhattacharjee , Kalpesh J. Haria , Jaydeb Sarkar

We show that the constrained characteristic function is a complete unitary invariant for J-constrained completely non-coisometric (c.n.c.) row contractions, where J is a WOT-closed two-sided ideal of the noncommutative analytic Toeplitz…

Operator Algebras · Mathematics 2007-05-23 Gelu Popescu

This article investigates $k$-regular factorizations of characteristic functions associated with completely non-coisometric row contractions. In this setting, a one-to-one correspondence is established between chains of joint invariant…

Functional Analysis · Mathematics 2026-05-29 Kalpesh J. Haria , Aashish Kumar Maurya

Let T:=[T_1,..., T_n] be an n-tuple of operators on a Hilbert space such that T is a completely non-coisometric row contraction. We establish the existence of a "one-to-one" correspondence between the joint invariant subspaces under…

Functional Analysis · Mathematics 2007-05-23 Gelu Popescu

Ergodic optimization aims to describe dynamically invariant probability measures that maximize the integral of a given function. For a wide class of intrinsically ergodic subshifts over a finite alphabet, we show that the space of…

Dynamical Systems · Mathematics 2026-04-15 Mao Shinoda , Hiroki Takahasi , Kenichiro Yamamoto

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

Based on a careful analysis of functional models for contractive multi-analytic operators we establish a one-to-one correspondence between unitary equivalence classes of minimal contractive liftings of a row contraction and injective…

Operator Algebras · Mathematics 2014-07-16 Santanu Dey , Rolf Gohm , Kalpesh J. Haria

The characteristic function for a contraction is a classical complete unitary invariant devised by Sz.-Nagy and Foias. Just as a contraction is related to the Szego kernel $k_S(z,w) = (1 - z\ow)^{-1}$ for $|z|, |w| < 1$, by means of…

Functional Analysis · Mathematics 2011-05-19 Angshuman Bhattacharya , Tirthankar Bhattacharyya

In this paper The Ergodic Hypothesis is proven for one class of functions defined in the infinite dimensional unite cube where is given an action of some semigroup of mappings without the condition on metric transitivity. The result has not…

General Mathematics · Mathematics 2011-03-01 Ilgar Sh. Jabbarov

We study a class of homeomorphisms of surfaces collectively known as linked-twist maps. We introduce an abstract definition which enables us to give a precise characterisation of a property observed by other authors, namely that such maps…

Dynamical Systems · Mathematics 2008-12-05 James Springham

This paper studies ergodic properties of certain measures arising in the dynamics of holomorphic correspondences. These measures, in general, are not invariant in the classical sense of ergodic theory. We define a notion of ergodicity, and…

Dynamical Systems · Mathematics 2024-12-11 Mayuresh Londhe

This is a survey on Reidemeister torsion for hyperbolic three-manifolds of finite volume. Torsions are viewed as topological invariants and also as functions on the variety of representations in $\operatorname{ SL}_2(\mathbb C)$. In both…

Geometric Topology · Mathematics 2016-05-27 Joan Porti

It is shown that a contraction on a Hilbert space is complex symmetric if and only if the values of its characteristic function are all symmetric with respect to a fixed conjugation. Applications are given to the description of complex…

Functional Analysis · Mathematics 2007-05-23 Nicolas Chevrot , Emmanuel Fricain , Dan Timotin

For any connected component $H_0$ of the space of real meromorphic functions we build a compactification $N(H_0)$ of the space $H_0$. Then we express the Euler characteristics of the spaces $H_0$ and $N(H_0)$ in terms of topological…

Complex Variables · Mathematics 2017-08-22 S. V. Shadrin
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