Stable and Historic Behavior in Replicator Equations Generated by Similar-Order Preserving Mappings

TL;DR

This paper introduces classes of replicator equations from similar-order preserving mappings that demonstrate both stable and historic behaviors, challenging traditional expectations in evolutionary game dynamics.

Contribution

It proposes new classes of replicator equations that exhibit stable and historic behaviors, expanding understanding of dynamics beyond classical zero-sum game results.

Findings

Replicator equations can have stable equilibria and historic oscillations.

Time averages may diverge in certain replicator dynamics.

New classes of equations challenge traditional Folk Theorem expectations.

Abstract

One could observe drastically different dynamics of zero-sum and non-zero-sum games under replicator equations. In zero-sum games, heteroclinic cycles naturally occur whenever the species of the population supersede each other in a cyclic fashion (like for the Rock-Paper-Scissors game). In this case, the highly erratic oscillations may cause the divergence of the time averages. In contrast, it is a common belief that the most ``reasonable" replicator equations of non-zero-sum games satisfy ``The Folk Theorem of Evolutionary Game Theory" which asserts that (i) a Nash equilibrium is a rest point; (ii) a stable rest point is a Nash equilibrium; (iii) a strictly Nash equilibrium is asymptotically stable; (iv) any interior convergent orbit evolves to a Nash equilibrium. In this paper, we propose two distinct vast classes of replicator equations generated by similar-order preserving mappings which exhibit stable as well as mean historic behavior. In the latter case, the time averages of the orbit will slowly oscillate during the evolution of the system and do not converge to any limit. This will eventually cause the divergence of higher-order repeated time averages.