Teaching an Old Dynamics New Tricks: Regularization-free Last-iterate Convergence in Zero-sum Games via BNN Dynamics

Fuente: arXiv
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Main Authors: Zhang, Tuo, Stella, Leonardo
Format: Preprint
Published: 2026
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author Zhang, Tuo
Stella, Leonardo
author_facet Zhang, Tuo
Stella, Leonardo
contents Zero-sum games are a fundamental setting for adversarial training and decision-making in multi-agent learning (MAL). Existing methods often ensure convergence to (approximate) Nash equilibria by introducing a form of regularization. Yet, regularization requires additional hyperparameters, which must be carefully tuned--a challenging task when the payoff structure is known, and considerably harder when the structure is unknown or subject to change. Motivated by this problem, we repurpose a classical model in evolutionary game theory, i.e., the Brown-von Neumann-Nash (BNN) dynamics, by leveraging the intrinsic convergence of this dynamics in zero-sum games without regularization, and provide last-iterate convergence guarantees in noisy normal-form games (NFGs). Importantly, to make this approach more applicable, we develop a novel framework with theoretical guarantees that integrates the BNN dynamics in extensive-form games (EFGs) through counterfactual weighting. Furthermore, we implement an algorithm that instantiates our framework with neural function approximation, enabling scalable learning in both NFGs and EFGs. Empirical results show that our method quickly adapts to nonstationarities, outperforming the state-of-the-art regularization-based approach.
format Preprint
id arxiv_https___arxiv_org_abs_2602_08938
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Teaching an Old Dynamics New Tricks: Regularization-free Last-iterate Convergence in Zero-sum Games via BNN Dynamics
Zhang, Tuo
Stella, Leonardo
Multiagent Systems
Zero-sum games are a fundamental setting for adversarial training and decision-making in multi-agent learning (MAL). Existing methods often ensure convergence to (approximate) Nash equilibria by introducing a form of regularization. Yet, regularization requires additional hyperparameters, which must be carefully tuned--a challenging task when the payoff structure is known, and considerably harder when the structure is unknown or subject to change. Motivated by this problem, we repurpose a classical model in evolutionary game theory, i.e., the Brown-von Neumann-Nash (BNN) dynamics, by leveraging the intrinsic convergence of this dynamics in zero-sum games without regularization, and provide last-iterate convergence guarantees in noisy normal-form games (NFGs). Importantly, to make this approach more applicable, we develop a novel framework with theoretical guarantees that integrates the BNN dynamics in extensive-form games (EFGs) through counterfactual weighting. Furthermore, we implement an algorithm that instantiates our framework with neural function approximation, enabling scalable learning in both NFGs and EFGs. Empirical results show that our method quickly adapts to nonstationarities, outperforming the state-of-the-art regularization-based approach.
title Teaching an Old Dynamics New Tricks: Regularization-free Last-iterate Convergence in Zero-sum Games via BNN Dynamics
topic Multiagent Systems
url https://arxiv.org/abs/2602.08938