Dynamics on Correlated Networks

Projects

A large complex network is modelled mathematically by its connectivity matrix, quantifying the interaction among its constituents. In neuroscience this matrix describes the strength of the connection between neurons and in ecology the competition among different species. For realistic models a theoretical or numerical analysis of such systems is often not feasible due to their high dimensionality and incomplete knowledge of the connectivity matrix. Many quantities of interest, such as the decay rate of neural activity or the stability of ecosystems, however, do not depend on the model details. They are universal and can be described within the framework of mathematically more accessible random matrix models. Together with two postdocs we will explore and classify such dynamic phenomena in strongly correlated networks.

Universal activity decay in neural networks

The dynamic properties of activity within a neural network are split into three separate regimes, depending on the relative strength of the connectivities between neurons and their tendency to have deminishing activity without external stimulation. In the regime with strong interactions the network exhibits exponentially growing activity and the dynamics are chaotic. This leads to an overstimulation of the network. If the neural interaction is weak, the network activity depletes exponentially in time, i.e. the network does not respond to the external stimulus. In between these two cases lies the critically tuned regime for which the network activity shows a power law decay. This power law is universal for a wide range of different networks as we showed in Randomly coupled differential equations with correlations and Power law decay for systems of randomly coupled differential equations. In this project we will extend the class of models for which this power law decay can be proved and investigate the bondaries of its validity.

Information propagation

We study the speed with which information propagates through a complex network, depending on its underlying geometric features. Particular emphasis will be placed on realistic models that reflect the structure of natural neural networks where the connections depend on the anatomy of dendrites. To this end we need to understand the complex spectrum of non-symmetric random matrices with intricate correlation structures amoung their entries. Such result can be found in our recent work Inhomogeneous Circular Law for Correlated Matrices.

News

  • 18 May 2021: Local elliptic law accepted for publication in the Bernoulli journal

  • 20 March 2021: Project 'Dynamics on Correlated Networks' announced at Department of Mathematical Sciences in Copenhagen (here).

  • 01 March 2021: Jonas Raunsø Håkånsen joins the project 'Dynamics on Correlated Networks' as research assistant

  • 01 January 2021: Start of Project 'Dynamics on Correlated Networks', funded by Novo Nordisk Foundation