Geivison Ribeiro

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20242026

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math.DS2025

The endpoint problem for $ε$ -hypercyclicity

Vinícius V. Fávaro, Geivison Ribeiro, Daniel Pellegrino +1

For a fixed $0 < ε < 1$ , F. Bayart asked in 2024 whether there exists an operator $T$ such that, for every $0 < δ < 1$ , $T$ is $δ$ -hypercyclic if and only if $δ\in[\varepsilon,1)…

math.FA2025

Operator Ranges and Spaceability: Extending a Result of Kitson and Timoney

Geivison Ribeiro

We revisit the results of Kitson and Timoney \emph{[J.~Math.~Anal.~Appl.~\textbf{378} (2011), 680--686]} on the spaceability of complements of operator ranges, extending one of the…

math.FA2025

An $ℓ^{1}$ -Isometric Subspace of $C [0, 1]$ with Countable Oscillating Spectrum

Geivison Ribeiro

In this paper we construct a closed subspace $X \subset C [0, 1]$ with countable oscillating spectrum $Ω (X)$ such that $X$ is isometric to $ℓ^{1}$ . This provides a negative answer to…

The endpoint problem for ε-hypercyclicity

Operator Ranges and Spaceability: Extending a Result of Kitson and Timoney

An ℓ1-Isometric Subspace of C[0,1] with Countable Oscillating Spectrum

The endpoint problem for $ε$ -hypercyclicity

An $ℓ^{1}$ -Isometric Subspace of $C [0, 1]$ with Countable Oscillating Spectrum