Extended real number arithmetics via Dedekind cuts

Fuente: arXiv
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1. Verfasser: Hamel, Andreas H
Format: Preprint
Veröffentlicht: 2026
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author Hamel, Andreas H
author_facet Hamel, Andreas H
contents It is shown how Dedekind cuts can be used to introduce the extended real numbers along with sound arithmetic laws via one simple rule for the addition of sets. The crucial idea is that the use of the lower and the upper part of the cuts, respectively, leads to two different additions which are known in the literature as inf-addition and sup-addition. Moreover, the two resulting structures are conlinear spaces which at the same time are complete lattices with respect to the natural order. This admits the definition of pseudo-differences on the extended reals which also provide formulas for expressions like $(+\infty) - (+\infty)$, $(-\infty) - (-\infty)$. There are two major motivations: one is that proper and improper extended real-valued functions can be treated in a unified manner, the other that set-valued functions can often be represented by families of scalar functions which may include improper ones.
format Preprint
id arxiv_https___arxiv_org_abs_2601_02229
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Extended real number arithmetics via Dedekind cuts
Hamel, Andreas H
Optimization and Control
49J53
It is shown how Dedekind cuts can be used to introduce the extended real numbers along with sound arithmetic laws via one simple rule for the addition of sets. The crucial idea is that the use of the lower and the upper part of the cuts, respectively, leads to two different additions which are known in the literature as inf-addition and sup-addition. Moreover, the two resulting structures are conlinear spaces which at the same time are complete lattices with respect to the natural order. This admits the definition of pseudo-differences on the extended reals which also provide formulas for expressions like $(+\infty) - (+\infty)$, $(-\infty) - (-\infty)$. There are two major motivations: one is that proper and improper extended real-valued functions can be treated in a unified manner, the other that set-valued functions can often be represented by families of scalar functions which may include improper ones.
title Extended real number arithmetics via Dedekind cuts
topic Optimization and Control
49J53
url https://arxiv.org/abs/2601.02229