Maximizing the algebraic connectivity in multilayer networks with arbitrary interconnections

TL;DR

This paper explores how to maximize the algebraic connectivity of multilayer networks with arbitrary interconnections by optimizing interlink weights within a budget, providing analytical bounds, convex reformulations, and heuristic placement strategies.

Contribution

It introduces a comprehensive framework for optimizing interlayer connections in multilayer networks, including analytical bounds, convex formulations, and heuristics for limited interlink placement.

Findings

Upper bounds for algebraic connectivity at low budgets independent of interconnection patterns

Convex reformulation of the optimization problem for numerical solutions

Heuristic algorithms for interlink placement based on Fiedler vector analysis

Abstract

The second smallest eigenvalue of the Laplacian matrix is determinative in characterizing many network properties and is known as algebraic connectivity. In this paper, we investigate the problem of maximizing algebraic connectivity in multilayer networks by allocating interlink weights subject to a budget while allowing arbitrary interconnections. For budgets below a threshold, we identify an upper-bound for maximum algebraic connectivity which is independent of interconnections pattern and is reachable with satisfying a certain regularity condition. For efficient numerical approaches in regions of no analytical solution, we cast the problem into a convex framework that explores the problem from several perspectives and, particularly, transforms into a graph embedding problem that is easier to interpret and related to the optimum diffusion phase. Allowing arbitrary interconnections entails regions of multiple transitions, giving more diverse diffusion phases with respect to one-to-one interconnection case. When there is no limitation on the interconnections pattern, we derive several analytical results characterizing the optimal weights by individual Fiedler vectors. We use the ratio of algebraic connectivity and the layer sizes to explain the results. Finally, we study the placement of a limited number of interlinks by greedy heuristics, using the Fiedler vector components of each layer.