Spurious phase in a model for traffic on a bridge

TL;DR

This paper uses high-precision Monte Carlo simulations to clarify the phase diagram of a two-species traffic model on a bridge, resolving debates about the existence of certain phases by showing they vanish in large or low-mobility systems.

Contribution

It provides definitive simulation evidence that one previously debated phase does not exist in large or low-mobility regimes, clarifying the model's phase structure.

Findings

Disputed phase disappears in large systems.

Disputed phase vanishes at low bulk mobility.

Clarifies the phase diagram of the traffic model.

Abstract

We present high-precision Monte Carlo data for the phase diagram of a two-species driven diffusive system, reminiscent of traffic across a narrow bridge. Earlier studies reported two phases with broken symmetry; the existence of one of these has been the subject of some debate. We show that the disputed phase disappears for sufficiently large systems and/or sufficiently low bulk mobility.