Upper Bound for Permanent Saturation of Metric Graphs using Interval Exchange Transformations

TL;DR

This paper improves upper bounds on the saturation time of metric graphs by leveraging the ergodic and minimal properties of interval exchange transformations, providing sharper estimates and new dynamical tools.

Contribution

It introduces a refined upper bound for saturation time using IETs and relates the Lyapunov spectrum to the system's dynamics, extending previous results.

Findings

Sharper upper bounds for saturation time are established.

The ergodic and minimal properties of IETs are utilized for analysis.

Simulations confirm the theoretical estimates on specific graph configurations.

Abstract

We refine upper bounds on the permanent saturation time of metric graphs using interval exchange transformations (IETs). Earlier results gave bounds under incommensurable edge lengths, we improve and generalize them by using the ergodic and minimal properties of IETs. By associating an IET to a metric graph, we show that the induced interval dynamics are ergodic and minimal, which ensures uniform coverage over time. Our main theorem gives a sharper upper bound for the saturation time in terms of edge lengths and structural constants of the graph. We also define the Lyapunov spectrum of the Kontsevich-Zorich cocycle for these maps and relate it to the system's dynamics. We validate our theoretical findings through simulations on specific graph configurations, such as the complete graph $K_4$ and star graphs, confirming the accuracy of our estimates. These results strengthen existing estimates and provide tools for studying connectivity at the interface of graph theory and dynamical systems.