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We prove several characterizations of $\mathscr{C}^{1,\omega}$-domains (aka Lyapunov domains), where $\omega$ is a growth function satisfying natural assumptions. For example, given an Ahlfors regular domain $\Omega\subseteq{\mathbb{R}}^n$,…

Classical Analysis and ODEs · Mathematics 2026-04-22 Juan José Marín , José María Martell , Dorina Mitrea , Marius Mitrea

We establish the full quasi-Banach range of $L^{p_1}(\mathbb R) \times L^{p_2}(\mathbb R) \rightarrow L^p(\mathbb R)$ bounds for one-dimensional bilinear singular integral operators with homogeneous kernels whose restriction $\Omega$ to the…

Classical Analysis and ODEs · Mathematics 2025-03-14 Petr Honzík , Stefanos Lappas , Lenka Slavíková

In the study of the cyclicity of a function $f$ in reproducing kernel Hilbert spaces an important role is played by sequences of polynomials $\{p_n\}_{n\in \mathbb{N}}$ called \emph{optimal polynomial approximants} (o.p.a.). For many such…

Complex Variables · Mathematics 2021-10-14 Antonio Acuaviva , Daniel Seco

The classical Enestrom-Kakeya theorem establishes upper and lower bounds on the zeros of a polynomial with positive coefficients that are explicit functions of those coefficients. We establish a unifying framework that incorporates this…

Complex Variables · Mathematics 2018-02-06 Aaron Melman

A linear map $u\colon \ E\to F$ between operator spaces is called completely co-bounded if it is completely bounded as a map from $E$ to the opposite of $F$. We give several simple results about completely co-bounded Schur multipliers on…

Functional Analysis · Mathematics 2014-12-23 Gilles Pisier

We decompose $p$ - integrable functions on the boundary of a simply connected Lipschitz domain $\Omega \subset \mathbb C$ into the sum of the boundary values of two, uniquely determined holomorphic functions, where one is holomorphic in…

Complex Variables · Mathematics 2025-02-18 Steven R. Bell , Loredana Lanzani , Nathan A. Wagner

We consider linear bounded operators acting in Banach spaces with a basis, such operators can be represented by an infinite matrix. We prove that for an invertible operator there exists a sequence of invertible finite-dimensional operators…

Functional Analysis · Mathematics 2024-03-12 Alexander Vasilyev , Vladimir Vasilyev , Abu Bakarr Kamanda Bongay

We shall give bounds on the spacing of zeros of certain functions belonging to the Laguerre-Polya class and satisfying a second order differential equation. As a corollary we establish new sharp inequalities on the extreme zeros of the…

Classical Analysis and ODEs · Mathematics 2016-09-07 Ilia Krasikov

We characterize diagonals of unbounded self-adjoint operators on a Hilbert space H that have only discrete spectrum, i.e., with empty essential spectrum. Our result extends the Schur-Horn theorem from a finite dimensional setting to an…

Functional Analysis · Mathematics 2017-05-04 Marcin Bownik , John Jasper , Bartłomiej Siudeja

We prove a polynomial Bogolyubov type lemma for the special linear group over finite fields. Specifically, we show that there exists an absolute constant $C>0,$ such that if $A$ is a density $\alpha$ subset of the special linear group, then…

Combinatorics · Mathematics 2024-12-20 Shai Evra , Guy Kindler , Noam Lifshitz

In 2009, Borcea and Br\"and\'en characterize all linear operators on multivariate polynomials which preserve the property of being non-vanishing (stable) on products of prescribed open circular regions. We give a representation theoretic…

Complex Variables · Mathematics 2021-08-09 Jonathan Leake

Given a finite set of closed rational points of affine space over a field, we give a Gr\"obner basis for the lexicographic ordering of the ideal of polynomials which vanish at all given points. Our method is an alternative to the…

Commutative Algebra · Mathematics 2007-05-23 Mathias Lederer

We prove that the roots of a smooth monic polynomial with complex-valued coefficients defined on a bounded Lipschitz domain $\Omega$ in $\mathbb R^m$ admit a parameterization by functions of bounded variation uniformly with respect to the…

Classical Analysis and ODEs · Mathematics 2021-04-06 Adam Parusinski , Armin Rainer

We study the spectrum of spherically symmetric Dirac operators in three-dimensional space with potentials tending to infinity at infinity under weak regularity assumptions. We prove that purely absolutely continuous spectrum covers the…

Spectral Theory · Mathematics 2007-05-23 Karl Michael Schmidt , Osanobu Yamada

Given an arbitrary infinite 0--1 matrix A having no identically zero rows, we define an algebra OA as the universal C*-algebra generated by partial isometries subject to conditions that generalize, to the infinite case, those introduced by…

funct-an · Mathematics 2007-05-23 Ruy Exel , Marcelo Laca

Let $\Omega$ be a bounded open interval, let $p>1$ and $\gamma>0$, and let $m:\Omega\rightarrow\mathbb{R}$ be a function that may change sign in $\Omega $. In this article we study the existence and nonexistence of positive solutions for…

Classical Analysis and ODEs · Mathematics 2015-10-06 Uriel Kaufmann , Iván Medri

Let $\Omega\subset\mathbb{R}^\nu$, $\nu\ge 2$, be a $C^{1,1}$ domain whose boundary $\partial\Omega$ is either compact or behaves suitably at infinity. For $p\in(1,\infty)$ and $\alpha>0$, define \[…

Spectral Theory · Mathematics 2017-04-27 Hynek Kovarik , Konstantin Pankrashkin

Let G be a locally compact group L^p(G) be the usual L^p-space for 1 =< p =< infty and A(G) be the Fourier algebra of G. Our goal is to study, in a new abstract context, the completely bounded multipliers of A(G), which we denote…

Functional Analysis · Mathematics 2007-05-23 Nico Spronk

In this paper, the authors establish the existence and boundedness of multilinear Littlewood--Paley operators on products of BMO spaces, including the multilinear $g$-function, multilinear Lusin's area integral and multilinear…

Classical Analysis and ODEs · Mathematics 2025-05-16 Runzhe Zhang , Hua Wang

The purpose of this paper is to provide a detailed description of the spaces that can be specified as $L^2$ domains for the operators of a first order elliptic complex on a compact manifold with conical singularities. This entails an…

Analysis of PDEs · Mathematics 2016-11-22 Thomas Krainer , Gerardo A. Mendoza