The descriptive complexity of the set of arc-connected compact subsets of the plane

Fuente: arXiv
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Main Authors: Debs, Gabriel, Raymond, Jean Saint
Format: Preprint
Published: 2026
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author Debs, Gabriel
Raymond, Jean Saint
author_facet Debs, Gabriel
Raymond, Jean Saint
contents We compute the exact complexity of the set of all arc-connected compact subsets of $\boldmath R^2$, which turns out to be strictly higher than the classical $\boldmath Σ^1_1$ and $\boldmath Π^1_1$ classes of analytic and coanalytic sets, but stricly lower than the class $\boldmath Π^1_2$ which is the exact descriptive class of the set of all arc-connected compact subsets of $\boldmath R^3$.
format Preprint
id arxiv_https___arxiv_org_abs_2601_13135
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle The descriptive complexity of the set of arc-connected compact subsets of the plane
Debs, Gabriel
Raymond, Jean Saint
General Topology
Logic
54H05, 03E15
We compute the exact complexity of the set of all arc-connected compact subsets of $\boldmath R^2$, which turns out to be strictly higher than the classical $\boldmath Σ^1_1$ and $\boldmath Π^1_1$ classes of analytic and coanalytic sets, but stricly lower than the class $\boldmath Π^1_2$ which is the exact descriptive class of the set of all arc-connected compact subsets of $\boldmath R^3$.
title The descriptive complexity of the set of arc-connected compact subsets of the plane
topic General Topology
Logic
54H05, 03E15
url https://arxiv.org/abs/2601.13135