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Main Author: Bridges, Douglas S.
Format: Preprint
Published: 2025
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Online Access:https://arxiv.org/abs/2510.15123
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author Bridges, Douglas S.
author_facet Bridges, Douglas S.
contents In constructive mathematics the metric complement of a subset S of a metric space X is the set -S of points in X that are bounded away from S. In this note we discuss, within Bishop's constructive mathematics, the connection between the metric double complement, -(-K), and the logical double complement, not not K, where K is a convex subset of a normed linear space X. In particular, we prove that if K has inhabited interior, then -(-K) equals the interior of not not K, that the hypothesis of inhabited interior can be dropped in the finite-dimensional case, and that we cannot constructively replace the interior of not not K by that of K in these results.
format Preprint
id arxiv_https___arxiv_org_abs_2510_15123
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Metric Double Complements of Convex Sets
Bridges, Douglas S.
Logic
03F60, 52A05
In constructive mathematics the metric complement of a subset S of a metric space X is the set -S of points in X that are bounded away from S. In this note we discuss, within Bishop's constructive mathematics, the connection between the metric double complement, -(-K), and the logical double complement, not not K, where K is a convex subset of a normed linear space X. In particular, we prove that if K has inhabited interior, then -(-K) equals the interior of not not K, that the hypothesis of inhabited interior can be dropped in the finite-dimensional case, and that we cannot constructively replace the interior of not not K by that of K in these results.
title Metric Double Complements of Convex Sets
topic Logic
03F60, 52A05
url https://arxiv.org/abs/2510.15123