Turbulent Closed Relations

TL;DR

This paper extends the concept of turbulence from continuous dynamical systems to closed relations on compact metric spaces, exploring their entropy, structural properties, and implications for homeomorphisms with new examples and counterexamples.

Contribution

It introduces CR-turbulence and reverse CR-turbulence, analyzes their relation to entropy, and constructs explicit turbulent relations, advancing the understanding of turbulence beyond classical systems.

Findings

Finite closed relations have equivalent turbulence and entropy properties.

Examples show turbulence can exist without high entropy in general relations.

Homeomorphisms cannot exhibit turbulence or its weakened forms.

Abstract

This paper generalizes the classical notion of turbulence from dynamical systems generated by continuous functions to those defined by closed relations on compact metric spaces. Using the Mahavier product and the associated shift map, we introduce and explore CR-turbulence and reverse CR-turbulence, analyzing their relationship to topological entropy. A key focus is understanding when turbulence implies entropy and vice versa, with results showing that for finite closed relations, these properties are equivalent. However, examples are provided to demonstrate that this equivalence can fail for more general relations. We also construct a large class of explicit turbulent closed relations on the unit interval that are dynamically rich yet structurally simple. Additionally, since homeomorphisms cannot admit turbulence, we investigate a weakened notion of turbulence: separated, continuum-wise semi-turbulence for homeomorphisms, and then prove that smooth fans cannot support even this weaker form of turbulent dynamics. The paper includes new examples, counterexamples, and open questions that deepen the understanding of turbulence in non-classical settings.