Non-Markovian temporal networks with auto- and cross-correlated link dynamics

Abstract

Many of the biological, social and man-made networks around us are inherently dynamic, with their links switching on and off over time. The evolution of these networks is often non-Markovian, and the dynamics of their links correlated. Hence, to accurately model these networks, predict their evolution, and understand how information and other quantities propagate over them, the inclusion of both memory and dynamical dependencies between links is key. We here introduce a general class of models of temporal networks based on discrete autoregressive processes. As a case study we concentrate on a specific model within this class, generating temporal networks with a specified underlying backbone, and with precise control over the dynamical dependencies between links and the strength and length of their memories. In this network model the presence of each link is influenced by its own past activity and the past activities of other links, as specified by a coupling matrix, which directly controls the causal relations and correlations among links. We propose a method for estimating the models parameters and how to deal with heterogeneity and time-varying patterns, showing how the model allows for a more realistic description of real world temporal networks and also to predict their evolution. We then investigate the role that memory and correlations in link dynamics have on processes occurring over a temporal network by studying the speed of a spreading process, as measured by the time it takes for diffusion to reach equilibrium. Through both numerical simulations and analytical results, we are able to separate the roles of autocorrelations and neighbourhood correlations in link dynamics, showing that the speed of diffusion is non-monotonically dependent on the memory length, and that correlations among neighbouring links can speed up the spreading process, while autocorrelations slow it down.