The Dynamical Landscape of Beggar-My-Neighbour: Ultra-long Matches, Loops, and Infinite Matches

TL;DR

This paper provides a rigorous analysis of the Beggar-My-Neighbour card game, revealing statistical properties of match durations, identifying oscillatory patterns in ultra-long matches, and demonstrating the existence of non-terminating cycles through an automated detection algorithm.

Contribution

It introduces a formal state-space framework, analyzes the game's dynamical landscape, and develops an automated algorithm to identify infinite game cycles, addressing longstanding questions about game termination.

Findings

Match durations follow an approximate exponential decay with deviations.

Ultra-long matches exhibit multi-scale oscillatory and entropic patterns.

Non-terminating cycles are confirmed in standard and generalized game settings.

Abstract

We present a rigorous mathematical and computational analysis of the deterministic card game \emph{Beggar-My-Neighbour}. By establishing a formal state-space framework, we investigate the game's dynamical landscape, focussing on the dichotomy between terminating and non-terminating matches. Extensive numerical simulations reveal that the distribution of finite match durations \emph{approximates} an exponential decay, with relevant deviations, confirming an emergent memory-less dynamics. This statistical behaviour is further analysed in the context of ultra-long matches, where we identify characteristic multi-scale oscillatory patterns and entropic regimes. Theoretically, we address the problem of backwards determinism, formalising the lack of injectivity of the trick function even within the set of reachable states. Crucially, we contribute to the recent resolution of the long-standing question regarding the existence of infinite games. We introduce an automated `Infinite Loop Factory' algorithm which, by implementing adaptive insertion strategies, proves effective in identifying non-terminating cycles with balanced initial deck configurations, thereby confirming the existence of non-terminating dynamics in standard and generalised settings of the game.