Karl-Mikael Perfekt

activity

20112026

most citedThe multiplicative Hilbert matrix

57 citations · 347 across the 45 of their papers we have counts for

collaborators

49 papers

math.FA2026

A Fejér--Riesz inequality for Dirichlet series

Karl-Mikael Perfekt

We prove the following inequality for Dirichlet polynomials: \[ \int_0^1 |f(1/2+σ)|\,dσ\lesssim \lim_{T\to\infty} \frac{1}{2T} \int_{-T}^T |f(it)| \, dt. \] In particular, for a Di…

math.CA2026

Boundary-Weighted Fourier Inequalities for Convex Domains

Konstantinos Bampouras, Karl-Mikael Perfekt

We consider the natural family of Fourier inequalities for the Paley--Wiener space $PW^{q} (Ω)$ , consisting of $L^{q}$ -functions with Fourier support in a convex set $Ω\subset…

math.SP2026

Comparison inequalities for Dirichlet-to-Neumann maps

Denis S. Grebenkov, Michael Levitin, Karl-Mikael Perfekt +1

We prove comparison inequalities for Dirichlet-to-Neumann maps corresponding to different non-positive Helmholtz parameters. For convex domains our bounds are sharp, and the result…

math.FA2026

Recovering Product BMO from Schatten Hankel operators

Konstantinos Bampouras, Karl-Mikael Perfekt

We prove that if a small Hankel operator on the product Hardy space belongs to some Schatten class $S^{p}$ , $p < \infty$ , then it has a symbol in product BMO. In other words, the con…

math.CA2025

Characterizations for arbitrary Békollé-Bonami weights

Carlos Mudarra, Karl-Mikael Perfekt

We precisely characterize the relationships between the reverse Hölder inequality, the Fujii-Wilson condition, the Békollé-Bonami $B_{p}$ condition, the $B_{\infty}$ …

math.FA2024

Besov spaces and Schatten class Hankel operators for Hardy and Paley--Wiener spaces in higher dimensions

Konstantinos Bampouras, Karl-Mikael Perfekt

We consider Schatten class membership of Hankel operators on Paley--Wiener spaces of convex $Ω \subset R^{n}$ , both for bounded and unbounded domains. In particular, the clas…

math.CA2024

Almost periodicity and boundary values of Dirichlet series

Ole Fredrik Brevig, Athanasios Kouroupis, Karl-Mikael Perfekt

We employ almost periodicity to establish analogues of the Hardy--Stein identity and the Littlewood--Paley formula for Hardy spaces of Dirichlet series. A construction of Saksman a…

math.CA2023★ 1 cited

Restrictions of Békollé--Bonami weights and Bloch functions

Alberto Dayan, Adrián Llinares, Karl-Mikael Perfekt

We characterize the restrictions of Békollé--Bonami weights of bounded hyperbolic oscillation, to subsets of the unit disc, thus proving an analogue of Wolff's restriction theorem…

math.FA2023

Cyclicity and iterated logarithms in the Drury-Arveson space

Alexandru Aleman, Karl-Mikael Perfekt, Stefan Richter +2

Let $H_{d}^{2}$ be the Drury-Arveson space, and let $f \in H_{d}^{2}$ have bounded argument and no zeros in $B_{d}$ . We show that $f$ is cyclic in $H_{d}^{2}$ if and only if $lo g f$ bel…

math.FA2023

Cyclicity in the Drury-Arveson space and other weighted Besov spaces

Alexandru Aleman, Karl-Mikael Perfekt, Stefan Richter +2

Let $H$ be a space of analytic functions on the unit ball $B_{d}$ in $C^{d}$ with multiplier algebra $Mult (H)$ . A function $f\in \mathcal{H…

math.NA2023

On the spectrum of the double-layer operator on locally-dilation-invariant Lipschitz domains

Simon N. Chandler-Wilde, Raffael Hagger, Karl-Mikael Perfekt +1

We say that $Γ$ , the boundary of a bounded Lipschitz domain, is locally dilation invariant if, at each $x \in Γ$ , $Γ$ is either locally $C^{1}$ or locally coincides (in some coordinat…

math.NT2023

A note on Bohr's theorem for Beurling integer systems

Frederik Broucke, Athanasios Kouroupis, Karl-Mikael Perfekt

Given a sequence of frequencies ${λ_{n}}_{n \geq 1}$ , a corresponding generalized Dirichlet series is of the form $f (s) = \sum_{n \geq 1} a_{n} e^{- λ_{n} s}$ . We are interested in multiplicati…

math.FA2022★ 2 cited

Correction to: Weak product spaces of Dirichlet series

Ole Fredrik Brevig, Karl-Mikael Perfekt

We correct the proof of Theorem~8 in [\emph{Weak product spaces of Dirichlet series}, Integral Equations Operator Theory \textbf{86} (2016), no.~4, 453--473.]

math.FA2022★ 8 cited

Composition operators on weighted Hilbert spaces of Dirichlet series

Athanasios Kouroupis, Karl-Mikael Perfekt

We study composition operators of characteristic zero on weighted Hilbert spaces of Dirichlet series. For this purpose we demonstrate the existence of weighted mean counting functi…

math.FA2022★ 2 cited

The Nehari problem for the Paley--Wiener space of a disc

Ole Fredrik Brevig, Karl-Mikael Perfekt

There is a bounded Hankel operator on the Paley--Wiener space of a disc in $R^{2}$ which does not arise from a bounded symbol.

math.FA2021★ 2 cited

Orthogonal decomposition of composition operators on the $H^{2}$ space of Dirichlet series

Ole Fredrik Brevig, Karl-Mikael Perfekt

Let $H^{2}$ denote the Hilbert space of Dirichlet series with square-summable coefficients. We study composition operators $C_{φ}$ on $H^{2}$ which are gene…

math.FA2021★ 6 cited

The quasi-static plasmonic problem for polyhedra

Marta de León-Contreras, Karl-Mikael Perfekt

We characterize the essential spectrum of the plasmonic problem for polyhedra in $R^{3}$ . The description is particularly simple for convex polyhedra and permittivities $ε<…

math.NA2020

The Complex-Scaled Half-Space Matching Method

Anne-Sophie Bonnet-Ben Dhia, Simon N. Chandler-Wilde, Sonia Fliss +3

The Half-Space Matching (HSM) method has recently been developed as a new method for the solution of 2D scattering problems with complex backgrounds, providing an alternative to Pe…

math.FA2020★ 1 cited

Infinitely many embedded eigenvalues for the Neumann-Poincaré operator in 3D

Wei Li, Karl-Mikael Perfekt, Stephen P. Shipman

This article constructs a surface whose Neumann-Poincaré (NP) integral operator has infinitely many eigenvalues embedded in its essential spectrum. The surface is a sphere perturbe…

math.FA2020★ 17 cited

A mean counting function for Dirichlet series and compact composition operators

Ole Fredrik Brevig, Karl-Mikael Perfekt

We introduce a mean counting function for Dirichlet series, which plays the same role in the function theory of Hardy spaces of Dirichlet series as the Nevanlinna counting function…

math.FA2020★ 4 cited

The spectrum of some Hardy kernel matrices

Ole Fredrik Brevig, Karl-Mikael Perfekt, Alexander Pushnitski

For $α > 0$ we consider the operator $K_{α} : ℓ^{2} \to ℓ^{2}$ corresponding to the matrix \[\left(\frac{(nm)^{-\frac{1}{2}+α}}{[\max(n,m)]^{2α}}\right)_{n,m=1}^\infty.\] By int…

math.SP2019★ 10 cited

Plasmonic eigenvalue problem for corners: limiting absorption principle and absolute continuity in the essential spectrum

Karl-Mikael Perfekt

We consider the plasmonic eigenvalue problem for a general 2D domain with a curvilinear corner, studying the spectral theory of the Neumann--Poincaré operator of the boundary. A li…

math.FA2019

Atomic decompositions, two stars theorems, and distances for the Bourgain-Brezis-Mironescu space and other big spaces

Luigi D'Onofrio, Luigi Greco, Karl-Mikael Perfekt +2

Given a Banach space $E$ with a supremum-type norm induced by a collection of operators, we prove that $E$ is a dual space and provide an atomic decomposition of its predual. We ap…

math.CA2019

Rectangular summation of multiple Fourier series and multi-parametric capacity

Karl-Mikael Perfekt

We consider the class of multiple Fourier series associated with functions in the Dirichlet space of the polydisc. We prove that every such series is summable with respect to unres…

A Fejér--Riesz inequality for Dirichlet series

Boundary-Weighted Fourier Inequalities for Convex Domains

Comparison inequalities for Dirichlet-to-Neumann maps

Recovering Product BMO from Schatten Hankel operators

Characterizations for arbitrary Békollé-Bonami weights

Besov spaces and Schatten class Hankel operators for Hardy and Paley--Wiener spaces in higher dimensions

Almost periodicity and boundary values of Dirichlet series

Restrictions of Békollé--Bonami weights and Bloch functions

Cyclicity and iterated logarithms in the Drury-Arveson space

Cyclicity in the Drury-Arveson space and other weighted Besov spaces

On the spectrum of the double-layer operator on locally-dilation-invariant Lipschitz domains

A note on Bohr's theorem for Beurling integer systems

Correction to: Weak product spaces of Dirichlet series

Composition operators on weighted Hilbert spaces of Dirichlet series

The Nehari problem for the Paley--Wiener space of a disc

Orthogonal decomposition of composition operators on the H2 space of Dirichlet series

The quasi-static plasmonic problem for polyhedra

The Complex-Scaled Half-Space Matching Method

Infinitely many embedded eigenvalues for the Neumann-Poincaré operator in 3D

A mean counting function for Dirichlet series and compact composition operators

The spectrum of some Hardy kernel matrices

Plasmonic eigenvalue problem for corners: limiting absorption principle and absolute continuity in the essential spectrum

Atomic decompositions, two stars theorems, and distances for the Bourgain-Brezis-Mironescu space and other big spaces

Rectangular summation of multiple Fourier series and multi-parametric capacity

Orthogonal decomposition of composition operators on the $H^{2}$ space of Dirichlet series