The Attractor of the Replicator Dynamic in Zero-Sum Games

TL;DR

This paper characterizes the long-term behavior of the replicator dynamic in zero-sum games, revealing a unique attractor determined solely by players' preferences, independent of payoff magnitudes.

Contribution

It introduces the concept of a preference graph that uniquely determines the replicator attractor in zero-sum games, regardless of payoff values.

Findings

Existence of a unique global attractor for zero-sum games.

The attractor depends only on players' preference orders.

In symmetric games, the attractor is a tournament; in asymmetric, a response graph.

Abstract

In this paper we characterise the long-run behaviour of the replicator dynamic in zero-sum games (symmetric or non-symmetric). Specifically, we prove that every zero-sum game possesses a unique global replicator attractor, which we then characterise. Most surprisingly, this attractor depends only on each player's preference order over their own strategies and not on the cardinal payoff values, defined by a finite directed graph we call the game's preference graph. When the game is symmetric, this graph is a tournament whose nodes are strategies; when the game is not symmetric, this graph is the game's response graph. We discuss the consequences of our results on chain recurrence and Nash equilibria.