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We give a simplified exposition of Kummert's approach to proving that every matrix-valued rational inner function in two variables has a minimal unitary transfer function realization. A slight modification of the approach extends to…

Complex Variables · Mathematics 2022-03-04 Greg Knese

We generalize the notion of semi-normalized classes of systems of differential equations, study properties of such classes and extend the algebraic method of group classification to them. In particular, we prove the important theorems on…

Mathematical Physics · Physics 2024-09-02 Celestin Kurujyibwami , Dmytro R. Popovych , Roman O. Popovych

We carry out the complete group classification of the class of (1+1)-dimensional linear Schr\"odinger equations with complex-valued potentials. After introducing the notion of uniformly semi-normalized classes of differential equations, we…

Mathematical Physics · Physics 2018-03-07 Célestin Kurujyibwami , Peter Basarab-Horwath , Roman O. Popovych

We consider quasi-polynomial spaces of differential forms defined as weighted (with a positive weight) spaces of differential forms with polynomial coefficients. We show that the unisolvent set of functionals for such spaces on a simplex in…

Numerical Analysis · Mathematics 2020-04-01 Shuonan Wu , Ludmil T. Zikatanov

We give an explicit solution formula for the polynomial regression problem in terms of Schur polynomials and Vandermonde determinants. We thereby generalize the work of Chang, Deng, and Floater to the case of model functions of the form…

Rings and Algebras · Mathematics 2026-02-24 Hans-Christian Herbig , Daniel Herden , Christopher Seaton

Determining if a symmetric function is Schur-positive is a prevalent and, in general, a notoriously difficult problem. In this paper we study the Schur-positivity of a family of symmetric functions. Given a partition \lambda, we denote by…

Combinatorics · Mathematics 2013-10-11 Cristina Ballantine , Rosa Orellana

In this paper, we investigate the geometric properties of complex-valued pluriharmonic mappings defined over convex Reinhardt domains in $\mathbb{C}^n$. We first establish a multidimensional analogue of the Noshiro-Warschawski Theorem,…

Complex Variables · Mathematics 2026-02-03 Molla Basir Ahamed , Sujoy Majumder , Debabrata Pramanik

The probability content of a convex polyhedron with a multivariate normal distribution can be regarded as a real analytic function. We give a system of linear partial differential equations with polynomial coefficients for the function and…

Classical Analysis and ODEs · Mathematics 2015-07-31 Tamio Koyama

The Schur index in four-dimensional $\mathcal{N}=4$ super Yang-Mills theory with $U(N)$ gauge group has a natural two-parameter deformation. We find that a matrix integral in such a deformed Schur index can be exactly evaluated by using…

High Energy Physics - Theory · Physics 2025-03-07 Yasuyuki Hatsuda

We prove several results about functions which preserve the Schur-Agler class under Hadamard or coefficient-wise product. First, functions which preserve the Schur class necessarily preserve the Schur-Agler class. Second, ``moments'' of…

Functional Analysis · Mathematics 2025-07-15 Greg Knese

This paper is devoted to the study of general (Laurent) polynomial modifications of moment functionals on the unit circle, i.e., associated with hermitian Toeplitz matrices. We present a new approach which allows us to study polynomial…

Classical Analysis and ODEs · Mathematics 2009-08-19 M. J. Cantero , L. Moral , L. Velazquez

It is common in stability analysis to linearize a system and investigate the spectrum of the Jacobian matrix. This approach faces the challenge of determining the matrix spectrum when the coefficients depend on parameters or when the…

Dynamical Systems · Mathematics 2025-03-17 Ziyad AlSharawi , Jose S. Cánovas , Sadok Kallel

We provide a new proof of Alesker's Irreducibility Theorem. We first introduce a new localization technique for polynomial valuations on convex bodies, which we use to independently prove that smooth and translation invariant valuations are…

Metric Geometry · Mathematics 2025-12-01 Georg C. Hofstätter , Jonas Knoerr

DR-submodular functions encompass a broad class of functions which are generally non-convex and non-concave. We study the problem of minimizing any DR-submodular function, with continuous and general integer variables, under box constraints…

Optimization and Control · Mathematics 2023-09-07 Qimeng Yu , Simge Küçükyavuz

The affine inverse eigenvalue problem consists of identifying a real symmetric matrix with a prescribed set of eigenvalues in an affine space. Due to its ubiquity in applications, various instances of the problem have been widely studied in…

Optimization and Control · Mathematics 2019-11-07 Utkan Candogan , Yong Sheng Soh , Venkat Chandrasekaran

Let $\Omega$ be a bounded pseudoconvex domain in $\mathbb{C}^N$. Given a continuous plurisubharmonic function $u$ on $\Omega$, we construct a sequence of Gaussian analytic functions $f_n$ on $\Omega$ associated with $u$ such that…

Complex Variables · Mathematics 2025-03-21 Kiyoon Eum

The operator-valued Schur-class is defined to be the set of holomorphic functions $S$ mapping the unit disk into the space of contraction operators between two Hilbert spaces. There are a number of alternate characterizations: the operator…

Classical Analysis and ODEs · Mathematics 2011-11-09 Joseph A. Ball , Animikh Biswas , Quanlei Fang , Sanne ter Horst

We obtain a new formula to relate the value of a Schur polynomial with variables $(x_1,\ldots,x_N)$ with values of Schur polynomials at $(1,\ldots,1)$. This allows to study the limit shape of perfect matchings on a square hexagon lattice…

Probability · Mathematics 2021-09-30 Zhongyang Li

Explicit expressions are given for the actions and radial matrix elements of basic radial observables on multi-dimensional spaces in a continuous sequence of orthonormal bases for unitary SU(1,1) irreps. Explicit expressions are also given…

Mathematical Physics · Physics 2009-11-11 D. J. Rowe

In this note we show that on any compact subdomain of a K\"ahler manifold that admits sufficiently many global holomorphic functions, the products of harmonic functions form a complete set. This gives a positive answer to the linearized…

Analysis of PDEs · Mathematics 2018-05-03 Colin Guillarmou , Mikko Salo , Leo Tzou
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