C. Sahu

activity

20212026

collaborators

12 papers

math.FA2026

The operator-valued Schur-Agler class in infinitely many variables

Shubham Rastogi, Chaman Kumar Sahu

Motivated by a recent work of G. Knese [Canad. Math. Bull., 2026], we introduce the operator-valued Schur-Agler class in infinitely many variables, consisting of functions whose re…

math.FA2026

Isometric rigidity of complete Pick algebras on monomial varieties

Hamidul Ahmed, B. Krishna Das, Chaman Kumar Sahu

We establish a geometric rigidity theorem for a class of monomial varieties in finite-dimensional unit balls. Every ball automorphism mapping one such variety onto another is unita…

math-ph2026

Noncommutative Marcus-Ree inequality and Erdős channels

Repana Devendra, Chaman Kumar Sahu

Unital quantum channels are the noncommutative analogues of doubly stochastic matrices. In 1959, Marcus and Ree showed that the squared Frobenius norm of a doubly stochastic matrix…

math.FA2026

Unbounded Toeplitz operators and finite rank de Branges-Rovnyak spaces

Soumitra Ghara, MD Ramiz Reza, Chaman Kumar Sahu

Motivated by the recent developments of de Branges-Rovnyak spaces, we investigate the function theoretic aspects of finite rank de Branges-Rovnyak spaces $H (B)$ generated by row-va…

math.FA2026

Multiplicative linear functionals on reproducing kernel Hilbert spaces

Tirthankar Bhattacharyya, Jaikishan, Poornendu Kumar +1

The classical Gleason--Kahane--Zelazko theorem characterizes multiplicative linear functionals on a unital Banach algebra through the scalar identity $Λ (x^{2}) = Λ (x)^{2}$ . We develo…

math.FA2025

Multiplier varieties and multiplier algebras of CNP Dirichlet series kernels

Hamidul Ahmed, B. Krishna Das, Chaman Kumar Sahu

We investigate isometric and algebraic isomorphism problems for multiplier algebras associated with Dirichlet series kernels that possess the complete Nevanlinna-Pick (CNP) propert…

math.FA2025

Nevanlinna-Pick interpolation in the right half-plane

Sameer Chavan, Chaman Kumar Sahu

The Szegö-Dirichlet kernel of the right half-plane $H_{1/2}$ is given by $ϰ (s, u) = ζ (s + u),$ $s, u \in H_{1/2},$ where $ζ$ denotes the Riemann…

math.NT2025

On the abscissas of a Dirichlet series and its subseries supported on prime factorization

Chaman Kumar Sahu

For a sequence ${a_{n}}_{n \geq 1} \subseteq (0, \infty)$ and a Dirichlet series $f (s) = \sum_{n = 1}^{\infty} a_{n} n^{- s},$ let $σ_{a} (f)$ denote the abscissa of absolute convergence of…

math.FA2024

Helson matrices induced by measures

Sameer Chavan, Chaman Kumar Sahu, Kalyan B. Sinha

We discuss the boundedness, Schatten-class properties and scattering theory of Helson matrices. We also discuss a class of Helson matrices induced by positive and signed measures.…

math.FA2023

Multipliers of the Hilbert spaces of Dirichlet series

Chaman Kumar Sahu

For a sequence $w = {w_{j}}_{j = 2}^{\infty}$ of positive real numbers, consider the positive semi-definite kernel $κ_{\mathbf w}(s, u) = \sum_{j = 2}^\infty w_j j^{-s - \ove…

math.FA2021

Quasi-Invariance of the Dirichlet series kernels, Analytic symbols and Homogeneous operators

Sameer Chavan, Chaman Kumar Sahu

For a scalar matrix $a = (a_{m, n})_{m, n = 1}^{\infty},$ the Dirichlet series kernel $κ_{a}$ is the double Dirichlet series $κ_{\mathbf a}(s, u) = \sum_{m, n =1}^{\inf…

math.FA2021

Dirichlet polynomials and a moment problem

Sameer Chavan, Chaman Kumar Sahu

Consider a linear functional $L$ defined on the space $D [s]$ of Dirichlet polynomials with real coefficients and the set $D_{+} [s]$ of non-negative elements in $\ma…