arXiv subjects

Thiago R. Alves

Publications and source records attributed to Thiago R. Alves.

7 recordsLinked to original sources

arXiv2026

On hypercyclic spaces and (common) $\mathscr{U}$-frequently hypercyclic spaces

Let $B$ be an unilateral weighted backward shift on $\ell_p$, $1 \leq p < \infty$, that admits a $\mathscr{U}$-frequently hypercyclic subspace. We prove that $B$ admits such a subspace free of frequently hypercyclic vectors. The proof technique we develop also allows us to prove that $B$ admits a hypercyclic subspace free of $\mathscr{U}$-frequently hypercyclic vectors, and to solve a question posed by Bès and Menet in 2015 on the existence of common $\mathscr{U}$-frequently hypercyclic subspaces.

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arXiv2024

On frequently supercyclic operators and an F_Γ-hypercyclicity criterior with applications

Given a Furstenberg family F and a subset Γ of C, we introduce and explore the notions of F_Γ-hypercyclic operator and F-hypercyclic scalar set. First, the study of F_C-hypercyclic operators yields new interesting information about frequently supercyclic, U-frequently supercyclic, reiteratively supercyclic and supercyclic operators. Then we provide a criterion for identifying F_Γ-hypercyclic operators. As applications of this criterion, we show that any unilateral pseudo-shift operator on c_0(N) or l_p(N) is F_Γ-hypercyclic for every unbounded subset Γ of C. Moreover, under the same condition on Γ, we show that any separable infinite-dimensional Banach space supports an F_Γ-hypercyclic operator. Finally, our study provides sufficient and necessary conditions for a subset Γ of C to be a hypercyclic scalar set. These results give partial answers to a question raised by Charpentier, Ernst, and Menet in 2016.

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arXiv2024

On the set of supercyclic operators

In this article, we address a problem posed by F. Bayart regarding the existence of an infinite-dimensional closed vector subspace (excluding the null operator) within the set of supercyclic operators on Banach spaces. We resolve this problem by establishing the existence of the closed subspace. Furthermore, we prove that the set of supercyclic operators on $\ell_1$ contains, up to the null operator, an isometric copy of $\ell_1$.

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arXiv2023

On sets of extreme functions for Fatou's theorem

Bounded holomorphic functions on the disk have radial limits in almost every direction, as follows from Fatou's theorem. Given a zero-measure set $E$ in the torus $\mathbb T$, we study the set of functions such that $\lim_{r \to 1^{-}} f(r \, w)$ fails to exist for every $w\in E$ (such functions were first constructed by Lusin). We show that the set of Lusin-type functions, for a fixed zero-measure set $E$, contain algebras of algebraic dimension $\mathfrak{c}$ (except for the zero function). When the set $E$ is countable, we show also in the several-variable case that the Lusin-type functions contain infinite dimensional Banach spaces and, moreover, contain plenty of $\mathfrak{c}$-dimensional algebras. We also address the question for functions on infinitely many variables.

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arXiv2021

Spaceability of sets of p-compact maps

We provide quite sufficient conditions on the Banach spaces $E$ and $F$ in order to obtain the spaceability of the set of all linear operators from $E$ into $F$ which are $q$-compact but not $p$-compact. Also, under similar conditions over $E$, we prove that this set contains (up to the null operator) a copy of $\ell_s$ whenever $F = \ell_s$. Finally, we give some applications of our previous results to show the spaceability of some sets formed by non-linear mappings (polynomial and Lipschitz) which are $q$-compact but not $p$-compact. The spaceability in the space of holomorphic mappings determined by $p$-compact sets is also considered.

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arXiv2021

Algebras and Banach spaces of Dirichlet series with maximal Bohr's strip

We study linear and algebraic structures in sets of Dirichlet series with maximal Bohr's strip. More precisely, we consider a set $\mathscr M$ of Dirichlet series which are uniformly continuous on the right half plane and whose strip of uniform but not absolute convergence has maximal width, i.e., $\frac{1}{2}$. Considering the uniform norm, we show that $\mathscr M$ contains an isometric copy of $\ell_1$ (except zero) and is strongly $\aleph_0$-algebrable. Also, there is a dense $G_δ$ set such that any of its elements generates a free algebra contained in $\mathscr M\cup \{0\}$. Furthermore, we investigate $\mathscr{M}$ as a subset of the Hilbert space of Dirichlet series whose coefficients are square-summable. In this case, we prove that $\mathscr M$ contains an isometric copy of $\ell_2$ (except zero).

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arXiv2019

Holomorphic functions with large cluster sets

We study linear and algebraic structures in sets of bounded holomorphic functions on the ball which have large cluster sets at every possible point (i.e., every point on the sphere in several complex variables and every point of the closed unit ball of the bidual in the infinite dimensional case). We show that this set is strongly c-algebrable for all separable Banach spaces. For specific spaces including lp or duals of Lorentz sequence spaces, we have strongly c-algebrability and spaceability even for the subalgebra of uniformly continuous holomorphic functions on the ball.

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