Amiable and Almost Amiable Fixed Sets. Extension of the Brouwer Fixed Point Theorem

TL;DR

This paper extends fixed point theorems within descriptive proximity spaces, introducing amiable and almost amiable fixed sets, and provides new theoretical results including a variation of the Jordan Curve Theorem and a Fixed Cell Complex Theorem.

Contribution

It introduces the concepts of amiable and almost amiable fixed sets in descriptive proximity spaces, extending the Brouwer Fixed Point Theorem with new theoretical insights.

Findings

Definition of amiable fixed sets and their Betti numbers

Introduction of almost amiable fixed sets for approximate applications

Extension of the Brouwer Fixed Point Theorem and related topological results

Abstract

This paper introduces shape boundary regions in descriptive proximity forms of CW (Closure-finite Weak) spaces as a source of amiable fixed subsets as well as almost amiable fixed subsets of descriptive proximally continuous (dpc) maps. A dpc map is an extension of an Efremovi\v{c}-Smirnov proximally continuous (pc) map introduced during the early-1950s by V.A. Efremovi\v{c} and Yu. M. Smirnov. Amiable fixed sets and the Betti numbers of their free Abelian group representations are derived from dpc's relative to the description of the boundary region of the sets. Almost amiable fixed sets are derived from dpc's by relaxing the matching description requirement for the descriptive closeness of the sets. This relaxed form of amiable fixed sets works well for applications in which closeness of fixed sets is approximate rather than exact. A number of examples of amiable fixed sets are given in terms of wide ribbons. A bi-product of this work is a variation of the Jordan Curve Theorem and a Fixed Cell Complex Theorem, which is an extension of the Brouwer Fixed Point Theorem.