
arXiv: 2601.12187
Let $X$ be an uncountable Polish space and let $\mathcal{H}$ be the Hindman ideal, that is, the family of all $S\subseteq ω$ which are not $IP$-sets. For each sequence $x=(x_n)_{n \in ω}$ taking values in $X$, let $Λ_{x}(FS)$ be the set of $IP$-limit points of $x$. Also, let $Λ_{x}(\mathcal{H})$ be the set of $\mathcal{H}$-limit points of $x$, that is, the set of ordinary limits of subsequences $(x_n)_{n \in S}$ with $S\notin \mathcal{H}$. After proving that these two notions do not coincide in general, we show that both families of nonempty sets of the type $Λ_{x}(FS)$ and of the type $Λ_{x}(\mathcal{H})$ are precisely the class of nonempty analytic subsets of $X$. An analogous result holds also for Ramsey convergence. In the proofs, we use the concept of partition regular functions introduced in J. Symb. Log. (2024) [doi:10.1017/jsl.2024.8], which provide a unified approach to these types of convergence.
Logic, General Topology (math.GN), FOS: Mathematics, General Topology, Dynamical Systems (math.DS), Logic (math.LO), Dynamical Systems, 03E75, 05D10, 40A05, 54A20 (Primary) 03E05, 11B05, 28A05, 40A35 (Secondary)
Logic, General Topology (math.GN), FOS: Mathematics, General Topology, Dynamical Systems (math.DS), Logic (math.LO), Dynamical Systems, 03E75, 05D10, 40A05, 54A20 (Primary) 03E05, 11B05, 28A05, 40A35 (Secondary)
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