Konstantinos Bampouras

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20232026

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6 papers · 1 filter

math.FA2026

Helson Inequality, Hankel Operators, and Weak Factorization on Paley-Wiener spaces of Convex Domains

Konstantinos Bampouras

For any convex set $Ω \subset R^{n}$ that does not contain affine lines, we prove the inequality $$\int_Ω\frac{|\hat{f}(x)|^2}{ω_Ω(x)}\,dx\leq C(n)\|f\|_{L^1}^2,\quad \supp\ha…

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.FA2025

Nehari's Theorem and Hardy's inequality for Paley--Wiener spaces

Konstantinos Bampouras

Recently it was proven that for a convex subset of $R^{n}$ that has infinitely many extreme vectors, the Nehari theorem fails, that is, there exists a bounded Hankel opera…

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.FA2023

Norm attaining vectors and Hilbert points

Konstantinos Bampouras, Ole Fredrik Brevig

Let $H$ be a Hilbert space that can be embedded as a dense subspace of a Banach space $X$ such that the norm of the embedding is equal to $1$ . We consider the following statements…

math.FA2023

On the failure of the Nehari Theorem for Paley-Wiener spaces

Konstantinos Bampouras

Let $Ω$ be a nonempty, open and convex subset of $R^{n}$ . The Paley-Wiener space with respect to $Ω$ is defined to be the closed subspace of $L^{2} (R^{n})$ of fun…