Cascade processes in complex systems

Abstract

Cascade processes describe howdamages, failures, information, and influence propagate in complex systems. A small local perturbation in a complex system can often result in large-scale global devastation through a cascade of reactions. Understanding cascade processes is thus important for answering fundamental questions regarding the robust structures of complex systems and their natural evolution toward such structures. This thesis contributes to the understanding of cascade processes through an extension to the established theory and a data-driven study of real-world complex systems. The first half of this thesis is devoted to a theoretical exploration of a novel class of cascade processes known as link cascades. A simple model is proposed to elucidate the essential physics of link cascades and is then studied through both analytic solution and numerical simulation. The second half of this thesis then presents a study on two real-world complex systems, namely air traffic and wildfire. The results obtained for these systems not only illuminate how cascades emerge in complex systems, but also provide practical insights into the mitigation of air traffic congestion and reveal a possible connection between wildfire statistics and global climate change. As a coherent whole, the results presented in this thesis shed light on the intricate interplay between the dynamics and structure of complex systems in cascade processes.

Date of Award	2022
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Bradley Alan FOREMAN (Supervisor), Kwok Yee Michael WONG (Supervisor) & Sai Ping LI (Supervisor)