Hostname: page-component-cd9895bd7-gbm5v Total loading time: 0 Render date: 2024-12-27T19:23:30.575Z Has data issue: false hasContentIssue false

Properties of the Fixed Point Set of Contractive Multi-Functions

Published online by Cambridge University Press:  20 November 2018

Helga Schirmer*
Affiliation:
Carleton University, Ottawa, Ontario
Rights & Permissions [Opens in a new window]

Extract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

A well known theorem by S. Banach states that a contractive function f: XX on a complete metric space X has a fixed point, and that this fixed point is unique. This result has a partial extension to multi-functions: every contractive compact-valued multi-function on a complete metric space has a fixed point (see Definition 1 and Theorem 1 below). But simple examples show that this fixed point is no longer unique. We investigate some questions concerned with the properties of the fixed point set Φ of a contractive multi-function φ. Is, e.g., Φ connected if φ is connected-valued? Is Φ convex if φ is convex-valued? The answer is yes if X is the real line (§2), but examples in §3 and §4 show that in general the answer is no.

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 1970

References

1. Markin, J. T., A fixed point theorem for set valued mappings, Bull. Amer. Math. Soc. 74 (1968), 639-640.Google Scholar
2. Nadler, S. B. Jr., Multi-valued contractive mappings, Pacific J. Math. 30 (1969), 475-488.Google Scholar